4 files changed, 821 insertions, 522 deletions

diff --git a/src/clocks/config.rs b/src/clocks/config.rs
new file mode 100644
index 000000000..a517afcca
--- /dev/null
+++ b/src/clocks/config.rs
@@ -0,0 +1,199 @@
+//! Clock Configuration
+//!
+//! This module holds configuration types used for the system clocks. For
+//! configuration of individual peripherals, see [`super::periph_helpers`].
+
+use super::PoweredClock;
+
+/// This type represents a divider in the range 1..=256.
+///
+/// At a hardware level, this is an 8-bit register from 0..=255,
+/// which adds one.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub struct Div8(pub(super) u8);
+
+impl Div8 {
+    /// Store a "raw" divisor value that will divide the source by
+    /// `(n + 1)`, e.g. `Div8::from_raw(0)` will divide the source
+    /// by 1, and `Div8::from_raw(255)` will divide the source by
+    /// 256.
+    pub const fn from_raw(n: u8) -> Self {
+        Self(n)
+    }
+
+    /// Store a specific divisor value that will divide the source
+    /// by `n`. e.g. `Div8::from_divisor(1)` will divide the source
+    /// by 1, and `Div8::from_divisor(256)` will divide the source
+    /// by 256.
+    ///
+    /// Will return `None` if `n` is not in the range `1..=256`.
+    /// Consider [`Self::from_raw`] for an infallible version.
+    pub const fn from_divisor(n: u16) -> Option<Self> {
+        let Some(n) = n.checked_sub(1) else {
+            return None;
+        };
+        if n > (u8::MAX as u16) {
+            return None;
+        }
+        Some(Self(n as u8))
+    }
+
+    /// Convert into "raw" bits form
+    #[inline(always)]
+    pub const fn into_bits(self) -> u8 {
+        self.0
+    }
+
+    /// Convert into "divisor" form, as a u32 for convenient frequency math
+    #[inline(always)]
+    pub const fn into_divisor(self) -> u32 {
+        self.0 as u32 + 1
+    }
+}
+
+/// ```text
+///               ┌─────────────────────────────────────────────────────────┐
+///               │                                                         │
+///               │   ┌───────────┐  clk_out   ┌─────────┐                  │
+///    XTAL ──────┼──▷│ System    │───────────▷│         │       clk_in     │
+///               │   │  OSC      │ clkout_byp │   MUX   │──────────────────┼──────▷
+///   EXTAL ──────┼──▷│           │───────────▷│         │                  │
+///               │   └───────────┘            └─────────┘                  │
+///               │                                                         │
+///               │   ┌───────────┐ fro_hf_root  ┌────┐          fro_hf     │
+///               │   │ FRO180    ├───────┬─────▷│ CG │─────────────────────┼──────▷
+///               │   │           │       │      ├────┤         clk_45m     │
+///               │   │           │       └─────▷│ CG │─────────────────────┼──────▷
+///               │   └───────────┘              └────┘                     │
+///               │   ┌───────────┐ fro_12m_root  ┌────┐         fro_12m    │
+///               │   │ FRO12M    │────────┬─────▷│ CG │────────────────────┼──────▷
+///               │   │           │        │      ├────┤          clk_1m    │
+///               │   │           │        └─────▷│1/12│────────────────────┼──────▷
+///               │   └───────────┘               └────┘                    │
+///               │                                                         │
+///               │                  ┌──────────┐                           │
+///               │                  │000       │                           │
+///               │      clk_in      │          │                           │
+///               │  ───────────────▷│001       │                           │
+///               │      fro_12m     │          │                           │
+///               │  ───────────────▷│010       │                           │
+///               │    fro_hf_root   │          │                           │
+///               │  ───────────────▷│011       │              main_clk     │
+///               │                  │          │───────────────────────────┼──────▷
+/// clk_16k ──────┼─────────────────▷│100       │                           │
+///               │       none       │          │                           │
+///               │  ───────────────▷│101       │                           │
+///               │     pll1_clk     │          │                           │
+///               │  ───────────────▷│110       │                           │
+///               │       none       │          │                           │
+///               │  ───────────────▷│111       │                           │
+///               │                  └──────────┘                           │
+///               │                        ▲                                │
+///               │                        │                                │
+///               │                     SCG SCS                             │
+///               │ SCG-Lite                                                │
+///               └─────────────────────────────────────────────────────────┘
+///
+///
+///                      clk_in      ┌─────┐
+///                  ───────────────▷│00   │
+///                      clk_45m     │     │
+///                  ───────────────▷│01   │      ┌───────────┐   pll1_clk
+///                       none       │     │─────▷│   SPLL    │───────────────▷
+///                  ───────────────▷│10   │      └───────────┘
+///                      fro_12m     │     │
+///                  ───────────────▷│11   │
+///                                  └─────┘
+/// ```
+#[non_exhaustive]
+pub struct ClocksConfig {
+    /// FIRC, FRO180, 45/60/90/180M clock source
+    pub firc: Option<FircConfig>,
+    /// SIRC, FRO12M, clk_12m clock source
+    // NOTE: I don't think we *can* disable the SIRC?
+    pub sirc: SircConfig,
+    /// FRO16K clock source
+    pub fro16k: Option<Fro16KConfig>,
+}
+
+// FIRC/FRO180M
+
+/// ```text
+/// ┌───────────┐ fro_hf_root  ┌────┐   fro_hf
+/// │ FRO180M   ├───────┬─────▷│GATE│──────────▷
+/// │           │       │      ├────┤  clk_45m
+/// │           │       └─────▷│GATE│──────────▷
+/// └───────────┘              └────┘
+/// ```
+#[non_exhaustive]
+pub struct FircConfig {
+    /// Selected clock frequency
+    pub frequency: FircFreqSel,
+    /// Selected power state of the clock
+    pub power: PoweredClock,
+    /// Is the "fro_hf" gated clock enabled?
+    pub fro_hf_enabled: bool,
+    /// Is the "clk_45m" gated clock enabled?
+    pub clk_45m_enabled: bool,
+    /// Is the "fro_hf_div" clock enabled? Requires `fro_hf`!
+    pub fro_hf_div: Option<Div8>,
+}
+
+/// Selected FIRC frequency
+pub enum FircFreqSel {
+    /// 45MHz Output
+    Mhz45,
+    /// 60MHz Output
+    Mhz60,
+    /// 90MHz Output
+    Mhz90,
+    /// 180MHz Output
+    Mhz180,
+}
+
+// SIRC/FRO12M
+
+/// ```text
+/// ┌───────────┐ fro_12m_root  ┌────┐ fro_12m
+/// │ FRO12M    │────────┬─────▷│ CG │──────────▷
+/// │           │        │      ├────┤  clk_1m
+/// │           │        └─────▷│1/12│──────────▷
+/// └───────────┘               └────┘
+/// ```
+#[non_exhaustive]
+pub struct SircConfig {
+    pub power: PoweredClock,
+    // peripheral output, aka sirc_12mhz
+    pub fro_12m_enabled: bool,
+    /// Is the "fro_lf_div" clock enabled? Requires `fro_12m`!
+    pub fro_lf_div: Option<Div8>,
+}
+
+#[non_exhaustive]
+pub struct Fro16KConfig {
+    pub vsys_domain_active: bool,
+    pub vdd_core_domain_active: bool,
+}
+
+impl Default for ClocksConfig {
+    fn default() -> Self {
+        Self {
+            firc: Some(FircConfig {
+                frequency: FircFreqSel::Mhz45,
+                power: PoweredClock::NormalEnabledDeepSleepDisabled,
+                fro_hf_enabled: true,
+                clk_45m_enabled: true,
+                fro_hf_div: None,
+            }),
+            sirc: SircConfig {
+                power: PoweredClock::AlwaysEnabled,
+                fro_12m_enabled: true,
+                fro_lf_div: None,
+            },
+            fro16k: Some(Fro16KConfig {
+                vsys_domain_active: true,
+                vdd_core_domain_active: true,
+            }),
+        }
+    }
+}
diff --git a/src/clocks/mod.rs b/src/clocks/mod.rs
index e04f63b8e..c6606b1b6 100644
--- a/src/clocks/mod.rs
+++ b/src/clocks/mod.rs
@@ -1,47 +1,335 @@
-//! Clock control helpers (no magic numbers, PAC field access only).
-//! Provides reusable gate abstractions for peripherals used by the examples.
+//! # Clock Module
+//!
+//! For the MCX-A, we separate clock and peripheral control into two main stages:
+//!
+//! 1. At startup, e.g. when `embassy_mcxa::init()` is called, we configure the
+//!    core system clocks, including external and internal oscillators. This
+//!    configuration is then largely static for the duration of the program.
+//! 2. When HAL drivers are created, e.g. `Lpuart::new()` is called, the driver
+//!    is responsible for two main things:
+//!     * Ensuring that any required "upstream" core system clocks necessary for
+//!       clocking the peripheral is active and configured to a reasonable value
+//!     * Enabling the clock gates for that peripheral, and resetting the peripheral
+//!
+//! From a user perspective, only step 1 is visible. Step 2 is automatically handled
+//! by HAL drivers, using interfaces defined in this module.
+//!
+//! It is also possible to *view* the state of the clock configuration after [`init()`]
+//! has been called, using the [`with_clocks()`] function, which provides a view of the
+//! [`Clocks`] structure.
+//!
+//! ## For HAL driver implementors
+//!
+//! The majority of peripherals in the MCXA chip are fed from either a "hard-coded" or
+//! configurable clock source, e.g. selecting the FROM12M or `clk_1m` as a source. This
+//! selection, as well as often any pre-scaler division from that source clock, is made
+//! through MRCC registers.
+//!
+//! Any peripheral that is controlled through the MRCC register can automatically implement
+//! the necessary APIs using the `impl_cc_gate!` macro in this module. You will also need
+//! to define the configuration surface and steps necessary to fully configure that peripheral
+//! from a clocks perspective by:
+//!
+//! 1. Defining a configuration type in the [`periph_helpers`] module that contains any selects
+//!    or divisions available to the HAL driver
+//! 2. Implementing the [`periph_helpers::SPConfHelper`] trait, which should check that the
+//!    necessary input clocks are reasonable
+
 use core::cell::RefCell;
 
+use config::{ClocksConfig, FircConfig, FircFreqSel, Fro16KConfig, SircConfig};
 use mcxa_pac::scg0::firccsr::{FircFclkPeriphEn, FircSclkPeriphEn, Fircsten};
 use mcxa_pac::scg0::sirccsr::{SircClkPeriphEn, Sircsten};
 use periph_helpers::SPConfHelper;
 
 use crate::pac;
+pub mod config;
 pub mod periph_helpers;
 
+//
+// Statics/Consts
+//
+
+/// The state of system core clocks.
+///
+/// Initialized by [`init()`], and then unchanged for the remainder of the program.
+static CLOCKS: critical_section::Mutex<RefCell<Option<Clocks>>> = critical_section::Mutex::new(RefCell::new(None));
+
+//
+// Free functions
+//
+
+/// Initialize the core system clocks with the given [`ClocksConfig`].
+///
+/// This function should be called EXACTLY once at start-up, usually via a
+/// call to [`embassy_mcxa::init()`](crate::init()). Subsequent calls will
+/// return an error.
+pub fn init(settings: ClocksConfig) -> Result<(), ClockError> {
+    critical_section::with(|cs| {
+        if CLOCKS.borrow_ref(cs).is_some() {
+            Err(ClockError::AlreadyInitialized)
+        } else {
+            Ok(())
+        }
+    })?;
+
+    let mut clocks = Clocks::default();
+    let mut operator = ClockOperator {
+        clocks: &mut clocks,
+        config: &settings,
+
+        _mrcc0: unsafe { pac::Mrcc0::steal() },
+        scg0: unsafe { pac::Scg0::steal() },
+        syscon: unsafe { pac::Syscon::steal() },
+        vbat0: unsafe { pac::Vbat0::steal() },
+    };
+
+    operator.configure_firc_clocks()?;
+    operator.configure_sirc_clocks()?;
+    operator.configure_fro16k_clocks()?;
+    // TODO, everything downstream
+
+    critical_section::with(|cs| {
+        let mut clks = CLOCKS.borrow_ref_mut(cs);
+        assert!(clks.is_none(), "Clock setup race!");
+        *clks = Some(clocks);
+    });
+
+    Ok(())
+}
+
+/// Obtain the full clocks structure, calling the given closure in a critical section.
+///
+/// The given closure will be called with read-only access to the state of the system
+/// clocks. This can be used to query and return the state of a given clock.
+///
+/// As the caller's closure will be called in a critical section, care must be taken
+/// not to block or cause any other undue delays while accessing.
+///
+/// Calls to this function will not succeed until after a successful call to `init()`,
+/// and will always return None.
+pub fn with_clocks<R: 'static, F: FnOnce(&Clocks) -> R>(f: F) -> Option<R> {
+    critical_section::with(|cs| {
+        let c = CLOCKS.borrow_ref(cs);
+        let c = c.as_ref()?;
+        Some(f(c))
+    })
+}
+
+//
+// Structs/Enums
+//
+
+/// The `Clocks` structure contains the initialized state of the core system clocks
+///
+/// These values are configured by providing [`config::ClocksConfig`] to the [`init()`] function
+/// at boot time.
+#[derive(Default, Debug, Clone)]
+#[non_exhaustive]
+pub struct Clocks {
+    /// The `clk_in` is a clock provided by an external oscillator
+    pub clk_in: Option<Clock>,
+
+    // FRO180M stuff
+    //
+    /// `fro_hf_root` is the direct output of the `FRO180M` internal oscillator
+    ///
+    /// It is used to feed downstream clocks, such as `fro_hf`, `clk_45m`,
+    /// and `fro_hf_div`.
+    pub fro_hf_root: Option<Clock>,
+
+    /// `fro_hf` is the same frequency as `fro_hf_root`, but behind a gate.
+    pub fro_hf: Option<Clock>,
+
+    /// `clk_45` is a 45MHz clock, sourced from `fro_hf`.
+    pub clk_45m: Option<Clock>,
+
+    /// `fro_hf_div` is a configurable frequency clock, sourced from `fro_hf`.
+    pub fro_hf_div: Option<Clock>,
+
+    //
+    // End FRO180M
+
+    // FRO12M stuff
+    //
+    /// `fro_12m_root` is the direct output of the `FRO12M` internal oscillator
+    ///
+    /// It is used to feed downstream clocks, such as `fro_12m`, `clk_1m`,
+    /// `and `fro_lf_div`.
+    pub fro_12m_root: Option<Clock>,
+
+    /// `fro_12m` is the same frequency as `fro_12m_root`, but behind a gate.
+    pub fro_12m: Option<Clock>,
+
+    /// `clk_1m` is a 1MHz clock, sourced from `fro_12m`
+    pub clk_1m: Option<Clock>,
+
+    /// `fro_lf_div` is a configurable frequency clock, sourced from `fro_12m`
+    pub fro_lf_div: Option<Clock>,
+    //
+    // End FRO12M stuff
+    /// `clk_16k_vsys` is one of two outputs of the `FRO16K` internal oscillator.
+    ///
+    /// Also referred to as `clk_16k[0]` in the datasheet, it feeds peripherals in
+    /// the system domain, such as the CMP and RTC.
+    pub clk_16k_vsys: Option<Clock>,
+
+    /// `clk_16k_vdd_core` is one of two outputs of the `FRO16K` internal oscillator.
+    ///
+    /// Also referred to as `clk_16k[1]` in the datasheet, it feeds peripherals in
+    /// the VDD Core domain, such as the OSTimer or LPUarts.
+    pub clk_16k_vdd_core: Option<Clock>,
+
+    /// `main_clk` is the main clock used by the CPU, AHB, APB, IPS bus, and some
+    /// peripherals.
+    pub main_clk: Option<Clock>,
+
+    /// `pll1_clk` is the output of the main system PLL, `pll1`.
+    pub pll1_clk: Option<Clock>,
+}
+
+/// `ClockError` is the main error returned when configuring or checking clock state
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+#[non_exhaustive]
+pub enum ClockError {
+    /// The system clocks were never initialized by calling [`init()`]
+    NeverInitialized,
+    /// The [`init()`] function was called more than once
+    AlreadyInitialized,
+    /// The requested configuration was not possible to fulfill, as the system clocks
+    /// were not configured in a compatible way
+    BadConfig { clock: &'static str, reason: &'static str },
+    /// The requested configuration was not possible to fulfill, as the required system
+    /// clocks have not yet been implemented.
+    NotImplemented { clock: &'static str },
+    /// The requested peripheral could not be configured, as the steps necessary to
+    /// enable it have not yet been implemented.
+    UnimplementedConfig,
+}
+
+/// Information regarding a system clock
+#[derive(Debug, Clone)]
+pub struct Clock {
+    /// The frequency, in Hz, of the given clock
+    pub frequency: u32,
+    /// The power state of the clock, e.g. whether it is active in deep sleep mode
+    /// or not.
+    pub power: PoweredClock,
+}
+
+/// The power state of a given clock.
+///
+/// On the MCX-A, when Deep-Sleep is entered, any clock not configured for Deep Sleep
+/// mode will be stopped. This means that any downstream usage, e.g. by peripherals,
+/// will also stop.
+///
+/// In the future, we will provide an API for entering Deep Sleep, and if there are
+/// any peripherals that are NOT using an `AlwaysEnabled` clock active, entry into
+/// Deep Sleep will be prevented, in order to avoid misbehaving peripherals.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum PoweredClock {
+    /// The given clock will NOT continue running in Deep Sleep mode
+    NormalEnabledDeepSleepDisabled,
+    /// The given clock WILL continue running in Deep Sleep mode
+    AlwaysEnabled,
+}
+
+/// The ClockOperator is a private helper type that contains the methods used
+/// during system clock initialization.
+///
+/// # SAFETY
+///
+/// Concurrent access to clock-relevant peripheral registers, such as `MRCC`, `SCG`,
+/// `SYSCON`, and `VBAT` should not be allowed for the duration of the [`init()`] function.
+struct ClockOperator<'a> {
+    /// A mutable reference to the current state of system clocks
+    clocks: &'a mut Clocks,
+    /// A reference to the requested configuration provided by the caller of [`init()`]
+    config: &'a ClocksConfig,
+
+    // We hold on to stolen peripherals
+    _mrcc0: pac::Mrcc0,
+    scg0: pac::Scg0,
+    syscon: pac::Syscon,
+    vbat0: pac::Vbat0,
+}
+
 /// Trait describing an AHB clock gate that can be toggled through MRCC.
 pub trait Gate {
     type MrccPeriphConfig: SPConfHelper;
 
     /// Enable the clock gate.
+    ///
+    /// # SAFETY
+    ///
+    /// The current peripheral must be disabled prior to calling this method
     unsafe fn enable_clock();
 
     /// Disable the clock gate.
+    ///
+    /// # SAFETY
+    ///
+    /// There must be no active user of this peripheral when calling this method
     unsafe fn disable_clock();
 
     /// Drive the peripheral into reset.
+    ///
+    /// # SAFETY
+    ///
+    /// There must be no active user of this peripheral when calling this method
     unsafe fn assert_reset();
 
     /// Drive the peripheral out of reset.
+    ///
+    /// # SAFETY
+    ///
+    /// There must be no active user of this peripheral when calling this method
     unsafe fn release_reset();
 
-    /// Return whether the clock gate is currently enabled.
+    /// Return whether the clock gate for this peripheral is currently enabled.
     fn is_clock_enabled() -> bool;
 
-    /// .
+    /// Return whether the peripheral is currently held in reset.
     fn is_reset_released() -> bool;
 }
 
+/// This is the primary helper method HAL drivers are expected to call when creating
+/// an instance of the peripheral.
+///
+/// This method:
+///
+/// 1. Enables the MRCC clock gate for this peripheral
+/// 2. Calls the `G::MrccPeriphConfig::post_enable_config()` method, returning an error
+///    and re-disabling the peripheral if this fails.
+/// 3. Pulses the MRCC reset line, to reset the peripheral to the default state
+/// 4. Returns the frequency, in Hz that is fed into the peripheral, taking into account
+///    the selected upstream clock, as well as any division specified by `cfg`.
+///
+/// NOTE: if a clock is disabled, sourced from an "ambient" clock source, this method
+/// may return `Ok(0)`. In the future, this might be updated to return the correct
+/// "ambient" clock, e.g. the AHB/APB frequency.
+///
+/// # SAFETY
+///
+/// This peripheral must not yet be in use prior to calling `enable_and_reset`.
 #[inline]
-pub unsafe fn enable_and_reset<G: Gate>(cfg: &G::MrccPeriphConfig) -> Result<u32, ClockError> {
-    let freq = enable::<G>(cfg)?;
+pub(crate) unsafe fn enable_and_reset<G: Gate>(cfg: &G::MrccPeriphConfig) -> Result<u32, ClockError> {
+    let freq = enable::<G>(cfg).inspect_err(|_| disable::<G>())?;
     pulse_reset::<G>();
     Ok(freq)
 }
 
-/// Enable a clock gate for the given peripheral set.
+/// Enable the clock gate for the given peripheral.
+///
+/// Prefer [`enable_and_reset`] unless you are specifically avoiding a pulse of the reset, or need
+/// to control the duration of the pulse more directly.
+///
+/// # SAFETY
+///
+/// This peripheral must not yet be in use prior to calling `enable`.
 #[inline]
-pub unsafe fn enable<G: Gate>(cfg: &G::MrccPeriphConfig) -> Result<u32, ClockError> {
+pub(crate) unsafe fn enable<G: Gate>(cfg: &G::MrccPeriphConfig) -> Result<u32, ClockError> {
     G::enable_clock();
     while !G::is_clock_enabled() {}
     core::arch::asm!("dsb sy; isb sy", options(nomem, nostack, preserves_flags));
@@ -57,239 +345,184 @@ pub unsafe fn enable<G: Gate>(cfg: &G::MrccPeriphConfig) -> Result<u32, ClockErr
     })
 }
 
-pub unsafe fn disable<G: Gate>() {
+/// Disable the clock gate for the given peripheral.
+///
+/// # SAFETY
+///
+/// This peripheral must no longer be in use prior to calling `enable`.
+#[allow(dead_code)]
+#[inline]
+pub(crate) unsafe fn disable<G: Gate>() {
     G::disable_clock();
 }
 
 /// Check whether a gate is currently enabled.
+#[allow(dead_code)]
 #[inline]
-pub fn is_clock_enabled<G: Gate>() -> bool {
+pub(crate) fn is_clock_enabled<G: Gate>() -> bool {
     G::is_clock_enabled()
 }
 
 /// Release a reset line for the given peripheral set.
+///
+/// Prefer [`enable_and_reset`].
+///
+/// # SAFETY
+///
+/// This peripheral must not yet be in use prior to calling `release_reset`.
 #[inline]
-pub unsafe fn release_reset<G: Gate>() {
+pub(crate) unsafe fn release_reset<G: Gate>() {
     G::release_reset();
 }
 
 /// Assert a reset line for the given peripheral set.
+///
+/// Prefer [`enable_and_reset`].
+///
+/// # SAFETY
+///
+/// This peripheral must not yet be in use prior to calling `assert_reset`.
 #[inline]
-pub unsafe fn assert_reset<G: Gate>() {
+pub(crate) unsafe fn assert_reset<G: Gate>() {
     G::assert_reset();
 }
 
+/// Check whether the peripheral is held in reset.
 #[inline]
-pub unsafe fn is_reset_released<G: Gate>() -> bool {
+pub(crate) unsafe fn is_reset_released<G: Gate>() -> bool {
     G::is_reset_released()
 }
 
 /// Pulse a reset line (assert then release) with a short delay.
+///
+/// Prefer [`enable_and_reset`].
+///
+/// # SAFETY
+///
+/// This peripheral must not yet be in use prior to calling `release_reset`.
 #[inline]
-pub unsafe fn pulse_reset<G: Gate>() {
+pub(crate) unsafe fn pulse_reset<G: Gate>() {
     G::assert_reset();
     cortex_m::asm::nop();
     cortex_m::asm::nop();
     G::release_reset();
 }
 
-macro_rules! impl_cc_gate {
-    ($name:ident, $reg:ident, $field:ident, $config:ty) => {
-        impl Gate for crate::peripherals::$name {
-            type MrccPeriphConfig = $config;
-
-            #[inline]
-            unsafe fn enable_clock() {
-                let mrcc = unsafe { pac::Mrcc0::steal() };
-                mrcc.$reg().modify(|_, w| w.$field().enabled());
-            }
-
-            #[inline]
-            unsafe fn disable_clock() {
-                let mrcc = unsafe { pac::Mrcc0::steal() };
-                mrcc.$reg().modify(|_r, w| w.$field().disabled());
-            }
-
-            #[inline]
-            fn is_clock_enabled() -> bool {
-                let mrcc = unsafe { pac::Mrcc0::steal() };
-                mrcc.$reg().read().$field().is_enabled()
-            }
-
-            #[inline]
-            unsafe fn release_reset() {
-                let mrcc = unsafe { pac::Mrcc0::steal() };
-                mrcc.$reg().modify(|_, w| w.$field().enabled());
-            }
+//
+// `impl`s for structs/enums
+//
 
-            #[inline]
-            unsafe fn assert_reset() {
-                let mrcc = unsafe { pac::Mrcc0::steal() };
-                mrcc.$reg().modify(|_, w| w.$field().disabled());
-            }
-
-            #[inline]
-            fn is_reset_released() -> bool {
-                let mrcc = unsafe { pac::Mrcc0::steal() };
-                mrcc.$reg().read().$field().is_enabled()
-            }
+/// The [`Clocks`] type's methods generally take the form of "ensure X clock is active".
+///
+/// These methods are intended to be used by HAL peripheral implementors to ensure that their
+/// selected clocks are active at a suitable level at time of construction. These methods
+/// return the frequency of the requested clock, in Hertz, or a [`ClockError`].
+impl Clocks {
+    /// Ensure the `fro_lf_div` clock is active and valid at the given power state.
+    pub fn ensure_fro_lf_div_active(&self, at_level: &PoweredClock) -> Result<u32, ClockError> {
+        let Some(clk) = self.fro_lf_div.as_ref() else {
+            return Err(ClockError::BadConfig {
+                clock: "fro_lf_div",
+                reason: "required but not active",
+            });
+        };
+        if !clk.power.meets_requirement_of(at_level) {
+            return Err(ClockError::BadConfig {
+                clock: "fro_lf_div",
+                reason: "not low power active",
+            });
         }
-    };
-}
-
-pub struct UnimplementedConfig;
-impl SPConfHelper for UnimplementedConfig {
-    fn post_enable_config(&self, _clocks: &Clocks) -> Result<u32, ClockError> {
-        Err(ClockError::UnimplementedConfig)
+        Ok(clk.frequency)
     }
-}
 
-pub struct NoConfig;
-impl SPConfHelper for NoConfig {
-    fn post_enable_config(&self, _clocks: &Clocks) -> Result<u32, ClockError> {
-        Ok(0)
+    /// Ensure the `fro_hf` clock is active and valid at the given power state.
+    pub fn ensure_fro_hf_active(&self, at_level: &PoweredClock) -> Result<u32, ClockError> {
+        let Some(clk) = self.fro_hf.as_ref() else {
+            return Err(ClockError::BadConfig {
+                clock: "fro_hf",
+                reason: "required but not active",
+            });
+        };
+        if !clk.power.meets_requirement_of(at_level) {
+            return Err(ClockError::BadConfig {
+                clock: "fro_hf",
+                reason: "not low power active",
+            });
+        }
+        Ok(clk.frequency)
     }
-}
 
-pub mod gate {
-    use super::periph_helpers::{AdcConfig, LpuartConfig, OsTimerConfig};
-    use super::*;
+    /// Ensure the `fro_hf_div` clock is active and valid at the given power state.
+    pub fn ensure_fro_hf_div_active(&self, at_level: &PoweredClock) -> Result<u32, ClockError> {
+        let Some(clk) = self.fro_hf_div.as_ref() else {
+            return Err(ClockError::BadConfig {
+                clock: "fro_hf_div",
+                reason: "required but not active",
+            });
+        };
+        if !clk.power.meets_requirement_of(at_level) {
+            return Err(ClockError::BadConfig {
+                clock: "fro_hf_div",
+                reason: "not low power active",
+            });
+        }
+        Ok(clk.frequency)
+    }
 
-    // These peripherals have no additional upstream clocks or configuration required
-    // other than enabling through the MRCC gate.
-    impl_cc_gate!(PORT1, mrcc_glb_cc1, port1, NoConfig);
-    impl_cc_gate!(PORT2, mrcc_glb_cc1, port2, NoConfig);
-    impl_cc_gate!(PORT3, mrcc_glb_cc1, port3, NoConfig);
-    impl_cc_gate!(GPIO3, mrcc_glb_cc2, gpio3, NoConfig);
+    /// Ensure the `clk_in` clock is active and valid at the given power state.
+    pub fn ensure_clk_in_active(&self, _at_level: &PoweredClock) -> Result<u32, ClockError> {
+        Err(ClockError::NotImplemented { clock: "clk_in" })
+    }
 
-    impl_cc_gate!(OSTIMER0, mrcc_glb_cc1, ostimer0, OsTimerConfig);
-    impl_cc_gate!(LPUART2, mrcc_glb_cc0, lpuart2, LpuartConfig);
-    impl_cc_gate!(ADC1, mrcc_glb_cc1, adc1, AdcConfig);
-}
+    /// Ensure the `clk_16k_vsys` clock is active and valid at the given power state.
+    pub fn ensure_clk_16k_vsys_active(&self, _at_level: &PoweredClock) -> Result<u32, ClockError> {
+        // NOTE: clk_16k is always active in low power mode
+        Ok(self
+            .clk_16k_vsys
+            .as_ref()
+            .ok_or(ClockError::BadConfig {
+                clock: "clk_16k_vsys",
+                reason: "required but not active",
+            })?
+            .frequency)
+    }
 
-// /// Convenience helper enabling the PORT2 and LPUART2 gates required for the debug UART.
-// pub unsafe fn enable_uart2_port2(peripherals: &pac::Peripherals) {
-//     enable::<gate::Port2>(peripherals);
-//     enable::<gate::Lpuart2>(peripherals);
-// }
-
-// /// Convenience helper enabling the PORT3 and GPIO3 gates used by the LED in the examples.
-// pub unsafe fn enable_led_port(peripherals: &pac::Peripherals) {
-//     enable::<gate::Port3>(peripherals);
-//     enable::<gate::Gpio3>(peripherals);
-// }
-
-// /// Convenience helper enabling the OSTIMER0 clock gate.
-// pub unsafe fn enable_ostimer0(peripherals: &pac::Peripherals) {
-//     enable::<gate::Ostimer0>(peripherals);
-// }
-
-// pub unsafe fn select_uart2_clock(peripherals: &pac::Peripherals) {
-//     // Use FRO_LF_DIV (already running) MUX=0 DIV=0
-//     let mrcc = &peripherals.mrcc0;
-//     mrcc.mrcc_lpuart2_clksel().write(|w| w.mux().clkroot_func_0());
-//     mrcc.mrcc_lpuart2_clkdiv().write(|w| unsafe { w.bits(0) });
-// }
-
-// pub unsafe fn ensure_frolf_running(peripherals: &pac::Peripherals) {
-//     // Ensure FRO_LF divider clock is running (reset default HALT=1 stops it)
-//     let sys = &peripherals.syscon;
-//     sys.frolfdiv().modify(|_, w| {
-//         // DIV defaults to 0; keep it explicit and clear HALT
-//         unsafe { w.div().bits(0) }.halt().run()
-//     });
-// }
-
-// /// Compute the FRO_LF_DIV output frequency currently selected for LPUART2.
-// /// Assumes select_uart2_clock() has chosen MUX=0 (FRO_LF_DIV) and DIV is set in SYSCON.FRO_LF_DIV.
-// pub unsafe fn uart2_src_hz(peripherals: &pac::Peripherals) -> u32 {
-//     // SYSCON.FRO_LF_DIV: DIV field is simple divider: freq_out = 12_000_000 / (DIV+1) for many NXP parts.
-//     // On MCXA276 FRO_LF base is 12 MHz; our init keeps DIV=0, so result=12_000_000.
-//     // Read it anyway for future generality.
-//     let div = peripherals.syscon.frolfdiv().read().div().bits() as u32;
-//     let base = 12_000_000u32;
-//     base / (div + 1)
-// }
-
-// /// Enable clock gate and release reset for OSTIMER0.
-// /// Select OSTIMER0 clock source = 1 MHz root (working bring-up configuration).
-// pub unsafe fn select_ostimer0_clock_1m(peripherals: &pac::Peripherals) {
-//     let mrcc = &peripherals.mrcc0;
-//     mrcc.mrcc_ostimer0_clksel().write(|w| w.mux().clkroot_1m());
-// }
-
-// pub unsafe fn enable_adc(peripherals: &pac::Peripherals) {
-//     enable::<gate::Port1>(peripherals);
-//     enable::<gate::Adc1>(peripherals);
-// }
-
-// pub unsafe fn select_adc_clock(peripherals: &pac::Peripherals) {
-//     // Use FRO_LF_DIV (already running) MUX=0 DIV=0
-//     let mrcc = &peripherals.mrcc0;
-//     mrcc.mrcc_adc_clksel().write(|w| w.mux().clkroot_func_0());
-//     mrcc.mrcc_adc_clkdiv().write(|w| unsafe { w.bits(0) });
-// }
-
-// ==============================================
-
-/// This type represents a divider in the range 1..=256.
-///
-/// At a hardware level, this is an 8-bit register from 0..=255,
-/// which adds one.
-#[derive(Copy, Clone, Debug, PartialEq, Eq)]
-pub struct Div8(pub(super) u8);
-
-impl Div8 {
-    /// Store a "raw" divisor value that will divide the source by
-    /// `(n + 1)`, e.g. `Div8::from_raw(0)` will divide the source
-    /// by 1, and `Div8::from_raw(255)` will divide the source by
-    /// 256.
-    pub const fn from_raw(n: u8) -> Self {
-        Self(n)
+    /// Ensure the `clk_16k_vdd_core` clock is active and valid at the given power state.
+    pub fn ensure_clk_16k_vdd_core_active(&self, _at_level: &PoweredClock) -> Result<u32, ClockError> {
+        // NOTE: clk_16k is always active in low power mode
+        Ok(self
+            .clk_16k_vdd_core
+            .as_ref()
+            .ok_or(ClockError::BadConfig {
+                clock: "clk_16k_vdd_core",
+                reason: "required but not active",
+            })?
+            .frequency)
     }
 
-    /// Store a specific divisor value that will divide the source
-    /// by `n`. e.g. `Div8::from_divisor(1)` will divide the source
-    /// by 1, and `Div8::from_divisor(256)` will divide the source
-    /// by 256.
-    ///
-    /// Will return `None` if `n` is not in the range `1..=256`.
-    /// Consider [`Self::from_raw`] for an infallible version.
-    pub const fn from_divisor(n: u16) -> Option<Self> {
-        let Some(n) = n.checked_sub(1) else {
-            return None;
+    /// Ensure the `clk_1m` clock is active and valid at the given power state.
+    pub fn ensure_clk_1m_active(&self, at_level: &PoweredClock) -> Result<u32, ClockError> {
+        let Some(clk) = self.clk_1m.as_ref() else {
+            return Err(ClockError::BadConfig {
+                clock: "clk_1m",
+                reason: "required but not active",
+            });
         };
-        if n > (u8::MAX as u16) {
-            return None;
+        if !clk.power.meets_requirement_of(at_level) {
+            return Err(ClockError::BadConfig {
+                clock: "clk_1m",
+                reason: "not low power active",
+            });
         }
-        Some(Self(n as u8))
-    }
-
-    /// Convert into "raw" bits form
-    #[inline(always)]
-    pub const fn into_bits(self) -> u8 {
-        self.0
+        Ok(clk.frequency)
     }
 
-    /// Convert into "divisor" form, as a u32 for convenient frequency math
-    #[inline(always)]
-    pub const fn into_divisor(self) -> u32 {
-        self.0 as u32 + 1
+    /// Ensure the `pll1_clk_div` clock is active and valid at the given power state.
+    pub fn ensure_pll1_clk_div_active(&self, _at_level: &PoweredClock) -> Result<u32, ClockError> {
+        Err(ClockError::NotImplemented { clock: "pll1_clk_div" })
     }
 }
 
-#[derive(Debug, Clone)]
-pub struct Clock {
-    pub frequency: u32,
-    pub power: PoweredClock,
-}
-
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
-pub enum PoweredClock {
-    NormalEnabledDeepSleepDisabled,
-    AlwaysEnabled,
-}
-
 impl PoweredClock {
     /// Does THIS clock meet the power requirements of the OTHER clock?
     pub fn meets_requirement_of(&self, other: &Self) -> bool {
@@ -302,172 +535,11 @@ impl PoweredClock {
     }
 }
 
-/// ```text
-///               ┌─────────────────────────────────────────────────────────┐
-///               │                                                         │
-///               │   ┌───────────┐  clk_out   ┌─────────┐                  │
-///    XTAL ──────┼──▷│ System    │───────────▷│         │       clk_in     │
-///               │   │  OSC      │ clkout_byp │   MUX   │──────────────────┼──────▷
-///   EXTAL ──────┼──▷│           │───────────▷│         │                  │
-///               │   └───────────┘            └─────────┘                  │
-///               │                                                         │
-///               │   ┌───────────┐ fro_hf_root  ┌────┐          fro_hf     │
-///               │   │ FRO180    ├───────┬─────▷│ CG │─────────────────────┼──────▷
-///               │   │           │       │      ├────┤         clk_45m     │
-///               │   │           │       └─────▷│ CG │─────────────────────┼──────▷
-///               │   └───────────┘              └────┘                     │
-///               │   ┌───────────┐ fro_12m_root  ┌────┐         fro_12m    │
-///               │   │ FRO12M    │────────┬─────▷│ CG │────────────────────┼──────▷
-///               │   │           │        │      ├────┤          clk_1m    │
-///               │   │           │        └─────▷│1/12│────────────────────┼──────▷
-///               │   └───────────┘               └────┘                    │
-///               │                                                         │
-///               │                  ┌──────────┐                           │
-///               │                  │000       │                           │
-///               │      clk_in      │          │                           │
-///               │  ───────────────▷│001       │                           │
-///               │      fro_12m     │          │                           │
-///               │  ───────────────▷│010       │                           │
-///               │    fro_hf_root   │          │                           │
-///               │  ───────────────▷│011       │              main_clk     │
-///               │                  │          │───────────────────────────┼──────▷
-/// clk_16k ──────┼─────────────────▷│100       │                           │
-///               │       none       │          │                           │
-///               │  ───────────────▷│101       │                           │
-///               │     pll1_clk     │          │                           │
-///               │  ───────────────▷│110       │                           │
-///               │       none       │          │                           │
-///               │  ───────────────▷│111       │                           │
-///               │                  └──────────┘                           │
-///               │                        ▲                                │
-///               │                        │                                │
-///               │                     SCG SCS                             │
-///               │ SCG-Lite                                                │
-///               └─────────────────────────────────────────────────────────┘
-///
-///
-///                      clk_in      ┌─────┐
-///                  ───────────────▷│00   │
-///                      clk_45m     │     │
-///                  ───────────────▷│01   │      ┌───────────┐   pll1_clk
-///                       none       │     │─────▷│   SPLL    │───────────────▷
-///                  ───────────────▷│10   │      └───────────┘
-///                      fro_12m     │     │
-///                  ───────────────▷│11   │
-///                                  └─────┘
-/// ```
-#[non_exhaustive]
-pub struct ClocksConfig {
-    // FIRC, FRO180, 45/60/90/180M clock source
-    pub firc: Option<FircConfig>,
-    // NOTE: I don't think we *can* disable the SIRC?
-    pub sirc: SircConfig,
-    pub fro16k: Option<Fro16KConfig>,
-}
-
-// FIRC/FRO180M
-
-/// ```text
-/// ┌───────────┐ fro_hf_root  ┌────┐   fro_hf
-/// │ FRO180M   ├───────┬─────▷│GATE│──────────▷
-/// │           │       │      ├────┤  clk_45m
-/// │           │       └─────▷│GATE│──────────▷
-/// └───────────┘              └────┘
-/// ```
-#[non_exhaustive]
-pub struct FircConfig {
-    pub frequency: FircFreqSel,
-    pub power: PoweredClock,
-    /// Is the "fro_hf" gated clock enabled?
-    pub fro_hf_enabled: bool,
-    /// Is the "clk_45m" gated clock enabled?
-    pub clk_45m_enabled: bool,
-    /// Is the "fro_hf_div" clock enabled? Requires `fro_hf`!
-    pub fro_hf_div: Option<Div8>,
-}
-
-pub enum FircFreqSel {
-    Mhz45,
-    Mhz60,
-    Mhz90,
-    Mhz180,
-}
-
-// SIRC/FRO12M
-
-/// ```text
-/// ┌───────────┐ fro_12m_root  ┌────┐ fro_12m
-/// │ FRO12M    │────────┬─────▷│ CG │──────────▷
-/// │           │        │      ├────┤  clk_1m
-/// │           │        └─────▷│1/12│──────────▷
-/// └───────────┘               └────┘
-/// ```
-#[non_exhaustive]
-pub struct SircConfig {
-    pub power: PoweredClock,
-    // peripheral output, aka sirc_12mhz
-    pub fro_12m_enabled: bool,
-    /// Is the "fro_lf_div" clock enabled? Requires `fro_12m`!
-    pub fro_lf_div: Option<Div8>,
-}
-
-#[derive(Default, Debug, Clone)]
-#[non_exhaustive]
-pub struct Clocks {
-    pub clk_in: Option<Clock>,
-
-    // FRO180M stuff
-    //
-    pub fro_hf_root: Option<Clock>,
-    pub fro_hf: Option<Clock>,
-    pub clk_45m: Option<Clock>,
-    pub fro_hf_div: Option<Clock>,
-    //
-    // End FRO180M
-
-    // FRO12M stuff
-    pub fro_12m_root: Option<Clock>,
-    pub fro_12m: Option<Clock>,
-    pub clk_1m: Option<Clock>,
-    pub fro_lf_div: Option<Clock>,
-    //
-    // End FRO12M stuff
-    pub clk_16k_vsys: Option<Clock>,
-    pub clk_16k_vdd_core: Option<Clock>,
-    pub main_clk: Option<Clock>,
-    pub pll1_clk: Option<Clock>,
-}
-
-#[non_exhaustive]
-pub struct Fro16KConfig {
-    pub vsys_domain_active: bool,
-    pub vdd_core_domain_active: bool,
-}
-
-static CLOCKS: critical_section::Mutex<RefCell<Option<Clocks>>> = critical_section::Mutex::new(RefCell::new(None));
-
-#[derive(Debug, Copy, Clone, Eq, PartialEq)]
-#[cfg_attr(feature = "defmt", derive(defmt::Format))]
-#[non_exhaustive]
-pub enum ClockError {
-    NeverInitialized,
-    AlreadyInitialized,
-    BadConfig { clock: &'static str, reason: &'static str },
-    NotImplemented { clock: &'static str },
-    UnimplementedConfig,
-}
-
-struct ClockOperator<'a> {
-    clocks: &'a mut Clocks,
-    config: &'a ClocksConfig,
-
-    _mrcc0: pac::Mrcc0,
-    scg0: pac::Scg0,
-    syscon: pac::Syscon,
-    vbat0: pac::Vbat0,
-}
-
 impl ClockOperator<'_> {
+    /// Configure the FIRC/FRO180M clock family
+    ///
+    /// NOTE: Currently we require this to be a fairly hardcoded value, as this clock is used
+    /// as the main clock used for the CPU, AHB, APB, etc.
     fn configure_firc_clocks(&mut self) -> Result<(), ClockError> {
         const HARDCODED_ERR: Result<(), ClockError> = Err(ClockError::BadConfig {
             clock: "firc",
@@ -484,7 +556,7 @@ impl ClockOperator<'_> {
         }
         let base_freq = 45_000_000;
 
-        // Is the FIRC as expected?
+        // Now, check if the FIRC as expected for our hardcoded value
         let mut firc_ok = true;
 
         // Is the hardware currently set to the default 45MHz?
@@ -604,6 +676,7 @@ impl ClockOperator<'_> {
         Ok(())
     }
 
+    /// Configure the SIRC/FRO12M clock family
     fn configure_sirc_clocks(&mut self) -> Result<(), ClockError> {
         let SircConfig {
             power,
@@ -694,6 +767,7 @@ impl ClockOperator<'_> {
         Ok(())
     }
 
+    /// Configure the FRO16K/clk_16k clock family
     fn configure_fro16k_clocks(&mut self) -> Result<(), ClockError> {
         let Some(fro16k) = self.config.fro16k.as_ref() else {
             return Ok(());
@@ -735,145 +809,74 @@ impl ClockOperator<'_> {
     }
 }
 
-pub fn init(settings: ClocksConfig) -> Result<(), ClockError> {
-    critical_section::with(|cs| {
-        if CLOCKS.borrow_ref(cs).is_some() {
-            Err(ClockError::AlreadyInitialized)
-        } else {
-            Ok(())
-        }
-    })?;
-
-    let mut clocks = Clocks::default();
-    let mut operator = ClockOperator {
-        clocks: &mut clocks,
-        config: &settings,
-
-        _mrcc0: unsafe { pac::Mrcc0::steal() },
-        scg0: unsafe { pac::Scg0::steal() },
-        syscon: unsafe { pac::Syscon::steal() },
-        vbat0: unsafe { pac::Vbat0::steal() },
-    };
+//
+// Macros/macro impls
+//
 
-    operator.configure_firc_clocks()?;
-    operator.configure_sirc_clocks()?;
-    operator.configure_fro16k_clocks()?;
-    // TODO, everything downstream
+/// This macro is used to implement the [`Gate`] trait for a given peripheral
+/// that is controlled by the MRCC peripheral.
+macro_rules! impl_cc_gate {
+    ($name:ident, $reg:ident, $field:ident, $config:ty) => {
+        impl Gate for crate::peripherals::$name {
+            type MrccPeriphConfig = $config;
 
-    critical_section::with(|cs| {
-        let mut clks = CLOCKS.borrow_ref_mut(cs);
-        assert!(clks.is_none(), "Clock setup race!");
-        *clks = Some(clocks);
-    });
+            #[inline]
+            unsafe fn enable_clock() {
+                let mrcc = unsafe { pac::Mrcc0::steal() };
+                mrcc.$reg().modify(|_, w| w.$field().enabled());
+            }
 
-    Ok(())
-}
+            #[inline]
+            unsafe fn disable_clock() {
+                let mrcc = unsafe { pac::Mrcc0::steal() };
+                mrcc.$reg().modify(|_r, w| w.$field().disabled());
+            }
 
-/// Obtain the full clocks structure, calling the given closure in a critical section
-///
-/// NOTE: Clocks implements `Clone`,
-pub fn with_clocks<R: 'static, F: FnOnce(&Clocks) -> R>(f: F) -> Option<R> {
-    critical_section::with(|cs| {
-        let c = CLOCKS.borrow_ref(cs);
-        let c = c.as_ref()?;
-        Some(f(c))
-    })
-}
+            #[inline]
+            fn is_clock_enabled() -> bool {
+                let mrcc = unsafe { pac::Mrcc0::steal() };
+                mrcc.$reg().read().$field().is_enabled()
+            }
 
-impl Clocks {
-    pub fn ensure_fro_lf_div_active(&self, at_level: &PoweredClock) -> Result<u32, ClockError> {
-        let Some(clk) = self.fro_lf_div.as_ref() else {
-            return Err(ClockError::BadConfig {
-                clock: "fro_lf_div",
-                reason: "required but not active",
-            });
-        };
-        if !clk.power.meets_requirement_of(at_level) {
-            return Err(ClockError::BadConfig {
-                clock: "fro_lf_div",
-                reason: "not low power active",
-            });
-        }
-        Ok(clk.frequency)
-    }
+            #[inline]
+            unsafe fn release_reset() {
+                let mrcc = unsafe { pac::Mrcc0::steal() };
+                mrcc.$reg().modify(|_, w| w.$field().enabled());
+            }
 
-    pub fn ensure_fro_hf_active(&self, at_level: &PoweredClock) -> Result<u32, ClockError> {
-        let Some(clk) = self.fro_hf.as_ref() else {
-            return Err(ClockError::BadConfig {
-                clock: "fro_hf",
-                reason: "required but not active",
-            });
-        };
-        if !clk.power.meets_requirement_of(at_level) {
-            return Err(ClockError::BadConfig {
-                clock: "fro_hf",
-                reason: "not low power active",
-            });
-        }
-        Ok(clk.frequency)
-    }
+            #[inline]
+            unsafe fn assert_reset() {
+                let mrcc = unsafe { pac::Mrcc0::steal() };
+                mrcc.$reg().modify(|_, w| w.$field().disabled());
+            }
 
-    pub fn ensure_fro_hf_div_active(&self, at_level: &PoweredClock) -> Result<u32, ClockError> {
-        let Some(clk) = self.fro_hf_div.as_ref() else {
-            return Err(ClockError::BadConfig {
-                clock: "fro_hf_div",
-                reason: "required but not active",
-            });
-        };
-        if !clk.power.meets_requirement_of(at_level) {
-            return Err(ClockError::BadConfig {
-                clock: "fro_hf_div",
-                reason: "not low power active",
-            });
+            #[inline]
+            fn is_reset_released() -> bool {
+                let mrcc = unsafe { pac::Mrcc0::steal() };
+                mrcc.$reg().read().$field().is_enabled()
+            }
         }
-        Ok(clk.frequency)
-    }
-
-    pub fn ensure_clk_in_active(&self, _at_level: &PoweredClock) -> Result<u32, ClockError> {
-        Err(ClockError::NotImplemented { clock: "clk_in" })
-    }
-
-    pub fn ensure_clk_16k_vsys_active(&self, _at_level: &PoweredClock) -> Result<u32, ClockError> {
-        // NOTE: clk_16k is always active in low power mode
-        Ok(self
-            .clk_16k_vsys
-            .as_ref()
-            .ok_or(ClockError::BadConfig {
-                clock: "clk_16k_vsys",
-                reason: "required but not active",
-            })?
-            .frequency)
-    }
+    };
+}
 
-    pub fn ensure_clk_16k_vdd_core_active(&self, _at_level: &PoweredClock) -> Result<u32, ClockError> {
-        // NOTE: clk_16k is always active in low power mode
-        Ok(self
-            .clk_16k_vdd_core
-            .as_ref()
-            .ok_or(ClockError::BadConfig {
-                clock: "clk_16k_vdd_core",
-                reason: "required but not active",
-            })?
-            .frequency)
-    }
+/// This module contains implementations of MRCC APIs, specifically of the [`Gate`] trait,
+/// for various low level peripherals.
+pub(crate) mod gate {
+    use super::periph_helpers::{AdcConfig, LpuartConfig, NoConfig, OsTimerConfig};
+    use super::*;
 
-    pub fn ensure_clk_1m_active(&self, at_level: &PoweredClock) -> Result<u32, ClockError> {
-        let Some(clk) = self.clk_1m.as_ref() else {
-            return Err(ClockError::BadConfig {
-                clock: "clk_1m",
-                reason: "required but not active",
-            });
-        };
-        if !clk.power.meets_requirement_of(at_level) {
-            return Err(ClockError::BadConfig {
-                clock: "clk_1m",
-                reason: "not low power active",
-            });
-        }
-        Ok(clk.frequency)
-    }
+    // These peripherals have no additional upstream clocks or configuration required
+    // other than enabling through the MRCC gate. Currently, these peripherals will
+    // ALWAYS return `Ok(0)` when calling [`enable_and_reset()`] and/or
+    // [`SPConfHelper::post_enable_config()`].
+    impl_cc_gate!(PORT1, mrcc_glb_cc1, port1, NoConfig);
+    impl_cc_gate!(PORT2, mrcc_glb_cc1, port2, NoConfig);
+    impl_cc_gate!(PORT3, mrcc_glb_cc1, port3, NoConfig);
+    impl_cc_gate!(GPIO3, mrcc_glb_cc2, gpio3, NoConfig);
 
-    pub fn ensure_pll1_clk_div_active(&self, _at_level: &PoweredClock) -> Result<u32, ClockError> {
-        Err(ClockError::NotImplemented { clock: "pll1_clk_div" })
-    }
+    // These peripherals DO have meaningful configuration, and could fail if the system
+    // clocks do not match their needs.
+    impl_cc_gate!(OSTIMER0, mrcc_glb_cc1, ostimer0, OsTimerConfig);
+    impl_cc_gate!(LPUART2, mrcc_glb_cc0, lpuart2, LpuartConfig);
+    impl_cc_gate!(ADC1, mrcc_glb_cc1, adc1, AdcConfig);
 }
diff --git a/src/clocks/periph_helpers.rs b/src/clocks/periph_helpers.rs
index 1657bd7eb..e5b234c5b 100644
--- a/src/clocks/periph_helpers.rs
+++ b/src/clocks/periph_helpers.rs
@@ -1,7 +1,43 @@
+//! Peripheral Helpers
+//!
+//! The purpose of this module is to define the per-peripheral special handling
+//! required from a clocking perspective. Different peripherals have different
+//! selectable source clocks, and some peripherals have additional pre-dividers
+//! that can be used.
+//!
+//! See the docs of [`SPConfHelper`] for more details.
+
 use super::{ClockError, Clocks, PoweredClock};
 use crate::pac;
 
+/// Sealed Peripheral Configuration Helper
+///
+/// NOTE: the name "sealed" doesn't *totally* make sense because its not sealed yet in the
+/// embassy-mcxa project, but it derives from embassy-imxrt where it is. We should
+/// fix the name, or actually do the sealing of peripherals.
+///
+/// This trait serves to act as a per-peripheral customization for clocking behavior.
+///
+/// This trait should be implemented on a configuration type for a given peripheral, and
+/// provide the methods that will be called by the higher level operations like
+/// `embassy_mcxa::clocks::enable_and_reset()`.
 pub trait SPConfHelper {
+    /// This method is called AFTER a given MRCC peripheral has been enabled (e.g. un-gated),
+    /// but BEFORE the peripheral reset line is reset.
+    ///
+    /// This function should check that any relevant upstream clocks are enabled, are in a
+    /// reasonable power state, and that the requested configuration can be made. If any of
+    /// these checks fail, an `Err(ClockError)` should be returned, likely `ClockError::BadConfig`.
+    ///
+    /// This function SHOULD NOT make any changes to the system clock configuration, even
+    /// unsafely, as this should remain static for the duration of the program.
+    ///
+    /// This function WILL be called in a critical section, care should be taken not to delay
+    /// for an unreasonable amount of time.
+    ///
+    /// On success, this function MUST return an `Ok(freq)`, where `freq` is the frequency
+    /// fed into the peripheral, taking into account the selected source clock, as well as
+    /// any pre-divisors.
     fn post_enable_config(&self, clocks: &Clocks) -> Result<u32, ClockError>;
 }
 
@@ -65,6 +101,33 @@ impl Div4 {
     }
 }
 
+/// A basic type that always returns an error when `post_enable_config` is called.
+///
+/// Should only be used as a placeholder.
+pub struct UnimplementedConfig;
+
+impl SPConfHelper for UnimplementedConfig {
+    fn post_enable_config(&self, _clocks: &Clocks) -> Result<u32, ClockError> {
+        Err(ClockError::UnimplementedConfig)
+    }
+}
+
+/// A basic type that always returns `Ok(0)` when `post_enable_config` is called.
+///
+/// This should only be used for peripherals that are "ambiently" clocked, like `PORTn`
+/// peripherals, which have no selectable/configurable source clock.
+pub struct NoConfig;
+impl SPConfHelper for NoConfig {
+    fn post_enable_config(&self, _clocks: &Clocks) -> Result<u32, ClockError> {
+        Ok(0)
+    }
+}
+
+//
+// LPUart
+//
+
+/// Selectable clocks for Lpuart peripherals
 #[derive(Debug, Clone, Copy)]
 pub enum LpuartClockSel {
     /// FRO12M/FRO_LF/SIRC clock source, passed through divider
@@ -86,16 +149,26 @@ pub enum LpuartClockSel {
     None,
 }
 
+/// Which instance of the Lpuart is this?
+///
+/// Should not be directly selectable by end-users.
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub enum LpuartInstance {
+    /// Instance 0
     Lpuart0,
+    /// Instance 1
     Lpuart1,
+    /// Instance 2
     Lpuart2,
+    /// Instance 3
     Lpuart3,
+    /// Instance 4
     Lpuart4,
+    /// Instance 5
     Lpuart5,
 }
 
+/// Top level configuration for `Lpuart` instances.
 pub struct LpuartConfig {
     /// Power state required for this peripheral
     pub power: PoweredClock,
@@ -108,39 +181,6 @@ pub struct LpuartConfig {
     pub(crate) instance: LpuartInstance,
 }
 
-#[derive(Copy, Clone, Debug, PartialEq, Eq)]
-pub enum OstimerClockSel {
-    /// 16k clock, sourced from FRO16K (Vdd Core)
-    Clk16kVddCore,
-    /// 1 MHz Clock sourced from FRO12M
-    Clk1M,
-    /// Disabled
-    None,
-}
-
-pub struct OsTimerConfig {
-    pub power: PoweredClock,
-    pub source: OstimerClockSel,
-}
-
-#[derive(Copy, Clone, Debug, PartialEq, Eq)]
-pub enum AdcClockSel {
-    FroLfDiv,
-    FroHf,
-    ClkIn,
-    Clk1M,
-    Pll1ClkDiv,
-    None,
-}
-
-pub struct AdcConfig {
-    pub power: PoweredClock,
-    pub source: AdcClockSel,
-    pub div: Div4,
-}
-
-// impls
-
 impl SPConfHelper for LpuartConfig {
     fn post_enable_config(&self, clocks: &Clocks) -> Result<u32, ClockError> {
         // check that source is suitable
@@ -215,6 +255,29 @@ impl SPConfHelper for LpuartConfig {
     }
 }
 
+//
+// OSTimer
+//
+
+/// Selectable clocks for the OSTimer peripheral
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum OstimerClockSel {
+    /// 16k clock, sourced from FRO16K (Vdd Core)
+    Clk16kVddCore,
+    /// 1 MHz Clock sourced from FRO12M
+    Clk1M,
+    /// Disabled
+    None,
+}
+
+/// Top level configuration for the `OSTimer` peripheral
+pub struct OsTimerConfig {
+    /// Power state required for this peripheral
+    pub power: PoweredClock,
+    /// Selected clock source for this peripheral
+    pub source: OstimerClockSel,
+}
+
 impl SPConfHelper for OsTimerConfig {
     fn post_enable_config(&self, clocks: &Clocks) -> Result<u32, ClockError> {
         let mrcc0 = unsafe { pac::Mrcc0::steal() };
@@ -237,6 +300,37 @@ impl SPConfHelper for OsTimerConfig {
     }
 }
 
+//
+// Adc
+//
+
+/// Selectable clocks for the ADC peripheral
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum AdcClockSel {
+    /// Divided `fro_lf`/`clk_12m`/FRO12M source
+    FroLfDiv,
+    /// Gated `fro_hf`/`FRO180M` source
+    FroHf,
+    /// External Clock Source
+    ClkIn,
+    /// 1MHz clock sourced by a divided `fro_lf`/`clk_12m`
+    Clk1M,
+    /// Internal PLL output, with configurable divisor
+    Pll1ClkDiv,
+    /// No clock/disabled
+    None,
+}
+
+/// Top level configuration for the ADC peripheral
+pub struct AdcConfig {
+    /// Power state required for this peripheral
+    pub power: PoweredClock,
+    /// Selected clock-source for this peripheral
+    pub source: AdcClockSel,
+    /// Pre-divisor, applied to the upstream clock output
+    pub div: Div4,
+}
+
 impl SPConfHelper for AdcConfig {
     fn post_enable_config(&self, clocks: &Clocks) -> Result<u32, ClockError> {
         use mcxa_pac::mrcc0::mrcc_adc_clksel::Mux;
diff --git a/src/config.rs b/src/config.rs
index 93aed5a99..0939c11f1 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -1,5 +1,6 @@
 // HAL configuration (minimal), mirroring embassy-imxrt style
 
+use crate::clocks::config::ClocksConfig;
 use crate::interrupt::Priority;
 
 #[non_exhaustive]
@@ -7,6 +8,7 @@ pub struct Config {
     pub time_interrupt_priority: Priority,
     pub rtc_interrupt_priority: Priority,
     pub adc_interrupt_priority: Priority,
+    pub clock_cfg: ClocksConfig,
 }
 
 impl Default for Config {
@@ -15,6 +17,7 @@ impl Default for Config {
             time_interrupt_priority: Priority::from(0),
             rtc_interrupt_priority: Priority::from(0),
             adc_interrupt_priority: Priority::from(0),
+            clock_cfg: ClocksConfig::default(),
         }
     }
 }