rp/clocks: store clock frequencies in ram

don't recalculate clock frequencies every time they are asked for. while
this is not very often in practice it does consume a bunch of flash
space that cannot be optimized away, and was pulled in unconditionally
previously. while we technically only need the configured rosc, xosc and
gpin frequencies it is easier to store all frequencies (and much cheaper
at runtime too).

2 files changed, 184 insertions, 207 deletions

diff --git a/embassy-rp/src/clocks.rs b/embassy-rp/src/clocks.rs
index 2305a1e34..9e581f105 100644
--- a/embassy-rp/src/clocks.rs
+++ b/embassy-rp/src/clocks.rs
@@ -1,10 +1,39 @@
+use core::sync::atomic::{AtomicU16, AtomicU32, Ordering};
+
 use embassy_hal_common::{into_ref, PeripheralRef};
 use pac::clocks::vals::*;
 
 use crate::{pac, reset, Peripheral};
 
-// TODO fix terrible use of global here
-static mut XIN_HZ: u32 = 0;
+struct Clocks {
+    xosc: AtomicU32,
+    sys: AtomicU32,
+    reference: AtomicU32,
+    pll_sys: AtomicU32,
+    pll_usb: AtomicU32,
+    usb: AtomicU32,
+    adc: AtomicU32,
+    gpin0: AtomicU32,
+    gpin1: AtomicU32,
+    rosc: AtomicU32,
+    peri: AtomicU32,
+    rtc: AtomicU16,
+}
+
+static CLOCKS: Clocks = Clocks {
+    xosc: AtomicU32::new(0),
+    sys: AtomicU32::new(0),
+    reference: AtomicU32::new(0),
+    pll_sys: AtomicU32::new(0),
+    pll_usb: AtomicU32::new(0),
+    usb: AtomicU32::new(0),
+    adc: AtomicU32::new(0),
+    gpin0: AtomicU32::new(0),
+    gpin1: AtomicU32::new(0),
+    rosc: AtomicU32::new(0),
+    peri: AtomicU32::new(0),
+    rtc: AtomicU16::new(0),
+};
 
 #[repr(u8)]
 #[non_exhaustive]
@@ -29,12 +58,15 @@ pub struct ClockConfig {
     pub usb_clk: Option<UsbClkConfig>,
     pub adc_clk: Option<AdcClkConfig>,
     pub rtc_clk: Option<RtcClkConfig>,
+    pub gpin0_hz: Option<u32>,
+    pub gpin1_hz: Option<u32>,
 }
 
 impl ClockConfig {
     pub fn crystal(crystal_hz: u32) -> Self {
         Self {
             rosc: Some(RoscConfig {
+                hz: 6_500_000,
                 range: RoscRange::Medium,
                 drive_strength: [0; 8],
                 div: 16,
@@ -83,12 +115,15 @@ impl ClockConfig {
                 div_frac: 0,
                 phase: 0,
             }),
+            gpin0_hz: None,
+            gpin1_hz: None,
         }
     }
 
     pub fn rosc() -> Self {
         Self {
             rosc: Some(RoscConfig {
+                hz: 140_000_000,
                 range: RoscRange::High,
                 drive_strength: [0; 8],
                 div: 1,
@@ -118,6 +153,8 @@ impl ClockConfig {
                 div_frac: 171,
                 phase: 0,
             }),
+            gpin0_hz: None,
+            gpin1_hz: None,
         }
     }
 }
@@ -133,6 +170,11 @@ pub enum RoscRange {
 }
 
 pub struct RoscConfig {
+    /// Final frequency of the oscillator, after the divider has been applied.
+    /// The oscillator has a nominal frequency of 6.5MHz at medium range with
+    /// divider 16 and all drive strengths set to 0, other values should be
+    /// measured in situ.
+    pub hz: u32,
     pub range: RoscRange,
     pub drive_strength: [u8; 8],
     pub div: u16,
@@ -145,7 +187,7 @@ pub struct XoscConfig {
 }
 
 pub struct PllConfig {
-    pub refdiv: u32,
+    pub refdiv: u8,
     pub fbdiv: u16,
     pub post_div1: u8,
     pub post_div2: u8,
@@ -277,41 +319,60 @@ pub(crate) unsafe fn init(config: ClockConfig) {
     reset::reset(peris);
     reset::unreset_wait(peris);
 
-    if let Some(config) = config.rosc {
-        configure_rosc(config);
-    }
-
-    if let Some(config) = config.xosc {
-        XIN_HZ = config.hz;
+    let gpin0_freq = config.gpin0_hz.unwrap_or(0);
+    CLOCKS.gpin0.store(gpin0_freq, Ordering::Relaxed);
+    let gpin1_freq = config.gpin1_hz.unwrap_or(0);
+    CLOCKS.gpin1.store(gpin1_freq, Ordering::Relaxed);
 
-        pac::WATCHDOG.tick().write(|w| {
-            w.set_cycles((config.hz / 1_000_000) as u16);
-            w.set_enable(true);
-        });
+    let rosc_freq = match config.rosc {
+        Some(config) => configure_rosc(config),
+        None => 0,
+    };
+    CLOCKS.rosc.store(rosc_freq, Ordering::Relaxed);
 
-        // start XOSC
-        // datasheet mentions support for clock inputs into XIN, but doesn't go into
-        // how this is achieved. pico-sdk doesn't support this at all.
-        start_xosc(config.hz);
+    let (xosc_freq, pll_sys_freq, pll_usb_freq) = match config.xosc {
+        Some(config) => {
+            pac::WATCHDOG.tick().write(|w| {
+                w.set_cycles((config.hz / 1_000_000) as u16);
+                w.set_enable(true);
+            });
 
-        if let Some(sys_pll_config) = config.sys_pll {
-            configure_pll(pac::PLL_SYS, config.hz, sys_pll_config);
-        }
-        if let Some(usb_pll_config) = config.usb_pll {
-            configure_pll(pac::PLL_USB, config.hz, usb_pll_config);
+            // start XOSC
+            // datasheet mentions support for clock inputs into XIN, but doesn't go into
+            // how this is achieved. pico-sdk doesn't support this at all.
+            start_xosc(config.hz);
+
+            let pll_sys_freq = match config.sys_pll {
+                Some(sys_pll_config) => configure_pll(pac::PLL_SYS, config.hz, sys_pll_config),
+                None => 0,
+            };
+            let pll_usb_freq = match config.usb_pll {
+                Some(usb_pll_config) => configure_pll(pac::PLL_USB, config.hz, usb_pll_config),
+                None => 0,
+            };
+
+            (config.hz, pll_sys_freq, pll_usb_freq)
         }
-    }
+        None => (0, 0, 0),
+    };
+    CLOCKS.xosc.store(xosc_freq, Ordering::Relaxed);
+    CLOCKS.pll_sys.store(pll_sys_freq, Ordering::Relaxed);
+    CLOCKS.pll_usb.store(pll_usb_freq, Ordering::Relaxed);
 
-    let (ref_src, ref_aux) = {
+    let (ref_src, ref_aux, clk_ref_freq) = {
         use {ClkRefCtrlAuxsrc as Aux, ClkRefCtrlSrc as Src};
+        let div = config.ref_clk.div as u32;
+        assert!(div >= 1 && div <= 4);
         match config.ref_clk.src {
-            RefClkSrc::Xosc => (Src::XOSC_CLKSRC, Aux::CLKSRC_PLL_USB),
-            RefClkSrc::Rosc => (Src::ROSC_CLKSRC_PH, Aux::CLKSRC_PLL_USB),
-            RefClkSrc::PllUsb => (Src::CLKSRC_CLK_REF_AUX, Aux::CLKSRC_PLL_USB),
-            RefClkSrc::Gpin0 => (Src::CLKSRC_CLK_REF_AUX, Aux::CLKSRC_GPIN0),
-            RefClkSrc::Gpin1 => (Src::CLKSRC_CLK_REF_AUX, Aux::CLKSRC_GPIN1),
+            RefClkSrc::Xosc => (Src::XOSC_CLKSRC, Aux::CLKSRC_PLL_USB, xosc_freq / div),
+            RefClkSrc::Rosc => (Src::ROSC_CLKSRC_PH, Aux::CLKSRC_PLL_USB, rosc_freq / div),
+            RefClkSrc::PllUsb => (Src::CLKSRC_CLK_REF_AUX, Aux::CLKSRC_PLL_USB, pll_usb_freq / div),
+            RefClkSrc::Gpin0 => (Src::CLKSRC_CLK_REF_AUX, Aux::CLKSRC_GPIN0, gpin0_freq / div),
+            RefClkSrc::Gpin1 => (Src::CLKSRC_CLK_REF_AUX, Aux::CLKSRC_GPIN1, gpin1_freq / div),
         }
     };
+    assert!(clk_ref_freq != 0);
+    CLOCKS.reference.store(clk_ref_freq, Ordering::Relaxed);
     c.clk_ref_ctrl().write(|w| {
         w.set_src(ref_src);
         w.set_auxsrc(ref_aux);
@@ -322,22 +383,27 @@ pub(crate) unsafe fn init(config: ClockConfig) {
     });
 
     pac::WATCHDOG.tick().write(|w| {
-        w.set_cycles((clk_ref_freq() / 1_000_000) as u16);
+        w.set_cycles((clk_ref_freq / 1_000_000) as u16);
         w.set_enable(true);
     });
 
-    let (sys_src, sys_aux) = {
+    let (sys_src, sys_aux, clk_sys_freq) = {
         use {ClkSysCtrlAuxsrc as Aux, ClkSysCtrlSrc as Src};
-        match config.sys_clk.src {
-            SysClkSrc::Ref => (Src::CLK_REF, Aux::CLKSRC_PLL_SYS),
-            SysClkSrc::PllSys => (Src::CLKSRC_CLK_SYS_AUX, Aux::CLKSRC_PLL_SYS),
-            SysClkSrc::PllUsb => (Src::CLKSRC_CLK_SYS_AUX, Aux::CLKSRC_PLL_USB),
-            SysClkSrc::Rosc => (Src::CLKSRC_CLK_SYS_AUX, Aux::ROSC_CLKSRC),
-            SysClkSrc::Xosc => (Src::CLKSRC_CLK_SYS_AUX, Aux::XOSC_CLKSRC),
-            SysClkSrc::Gpin0 => (Src::CLKSRC_CLK_SYS_AUX, Aux::CLKSRC_GPIN0),
-            SysClkSrc::Gpin1 => (Src::CLKSRC_CLK_SYS_AUX, Aux::CLKSRC_GPIN1),
-        }
+        let (src, aux, freq) = match config.sys_clk.src {
+            SysClkSrc::Ref => (Src::CLK_REF, Aux::CLKSRC_PLL_SYS, clk_ref_freq),
+            SysClkSrc::PllSys => (Src::CLKSRC_CLK_SYS_AUX, Aux::CLKSRC_PLL_SYS, pll_sys_freq),
+            SysClkSrc::PllUsb => (Src::CLKSRC_CLK_SYS_AUX, Aux::CLKSRC_PLL_USB, pll_usb_freq),
+            SysClkSrc::Rosc => (Src::CLKSRC_CLK_SYS_AUX, Aux::ROSC_CLKSRC, rosc_freq),
+            SysClkSrc::Xosc => (Src::CLKSRC_CLK_SYS_AUX, Aux::XOSC_CLKSRC, xosc_freq),
+            SysClkSrc::Gpin0 => (Src::CLKSRC_CLK_SYS_AUX, Aux::CLKSRC_GPIN0, gpin0_freq),
+            SysClkSrc::Gpin1 => (Src::CLKSRC_CLK_SYS_AUX, Aux::CLKSRC_GPIN1, gpin1_freq),
+        };
+        assert!(config.sys_clk.div_int <= 0x1000000);
+        let div = config.sys_clk.div_int as u64 * 256 + config.sys_clk.div_frac as u64;
+        (src, aux, ((freq as u64 * 256) / div) as u32)
     };
+    assert!(clk_sys_freq != 0);
+    CLOCKS.sys.store(clk_sys_freq, Ordering::Relaxed);
     if sys_src != ClkSysCtrlSrc::CLK_REF {
         c.clk_sys_ctrl().write(|w| w.set_src(ClkSysCtrlSrc::CLK_REF));
         while c.clk_sys_selected().read() != 1 << ClkSysCtrlSrc::CLK_REF.0 {}
@@ -359,11 +425,23 @@ pub(crate) unsafe fn init(config: ClockConfig) {
             w.set_enable(true);
             w.set_auxsrc(ClkPeriCtrlAuxsrc(src as _));
         });
+        let peri_freq = match src {
+            PeriClkSrc::Sys => clk_sys_freq,
+            PeriClkSrc::PllSys => pll_sys_freq,
+            PeriClkSrc::PllUsb => pll_usb_freq,
+            PeriClkSrc::Rosc => rosc_freq,
+            PeriClkSrc::Xosc => xosc_freq,
+            PeriClkSrc::Gpin0 => gpin0_freq,
+            PeriClkSrc::Gpin1 => gpin1_freq,
+        };
+        assert!(peri_freq != 0);
+        CLOCKS.peri.store(peri_freq, Ordering::Relaxed);
     } else {
         peris.set_spi0(false);
         peris.set_spi1(false);
         peris.set_uart0(false);
         peris.set_uart1(false);
+        CLOCKS.peri.store(0, Ordering::Relaxed);
     }
 
     if let Some(conf) = config.usb_clk {
@@ -373,8 +451,20 @@ pub(crate) unsafe fn init(config: ClockConfig) {
             w.set_enable(true);
             w.set_auxsrc(ClkUsbCtrlAuxsrc(conf.src as _));
         });
+        let usb_freq = match conf.src {
+            UsbClkSrc::PllUsb => pll_usb_freq,
+            UsbClkSrc::PllSys => pll_sys_freq,
+            UsbClkSrc::Rosc => rosc_freq,
+            UsbClkSrc::Xosc => xosc_freq,
+            UsbClkSrc::Gpin0 => gpin0_freq,
+            UsbClkSrc::Gpin1 => gpin1_freq,
+        };
+        assert!(usb_freq != 0);
+        assert!(conf.div >= 1 && conf.div <= 4);
+        CLOCKS.usb.store(usb_freq / conf.div as u32, Ordering::Relaxed);
     } else {
         peris.set_usbctrl(false);
+        CLOCKS.usb.store(0, Ordering::Relaxed);
     }
 
     if let Some(conf) = config.adc_clk {
@@ -384,8 +474,20 @@ pub(crate) unsafe fn init(config: ClockConfig) {
             w.set_enable(true);
             w.set_auxsrc(ClkAdcCtrlAuxsrc(conf.src as _));
         });
+        let adc_in_freq = match conf.src {
+            AdcClkSrc::PllUsb => pll_usb_freq,
+            AdcClkSrc::PllSys => pll_sys_freq,
+            AdcClkSrc::Rosc => rosc_freq,
+            AdcClkSrc::Xosc => xosc_freq,
+            AdcClkSrc::Gpin0 => gpin0_freq,
+            AdcClkSrc::Gpin1 => gpin1_freq,
+        };
+        assert!(adc_in_freq != 0);
+        assert!(conf.div >= 1 && conf.div <= 4);
+        CLOCKS.adc.store(adc_in_freq / conf.div as u32, Ordering::Relaxed);
     } else {
         peris.set_adc(false);
+        CLOCKS.adc.store(0, Ordering::Relaxed);
     }
 
     if let Some(conf) = config.rtc_clk {
@@ -401,15 +503,30 @@ pub(crate) unsafe fn init(config: ClockConfig) {
             w.set_enable(true);
             w.set_auxsrc(ClkRtcCtrlAuxsrc(conf.src as _));
         });
+        let rtc_in_freq = match conf.src {
+            RtcClkSrc::PllUsb => pll_usb_freq,
+            RtcClkSrc::PllSys => pll_sys_freq,
+            RtcClkSrc::Rosc => rosc_freq,
+            RtcClkSrc::Xosc => xosc_freq,
+            RtcClkSrc::Gpin0 => gpin0_freq,
+            RtcClkSrc::Gpin1 => gpin1_freq,
+        };
+        assert!(rtc_in_freq != 0);
+        assert!(config.sys_clk.div_int <= 0x1000000);
+        CLOCKS.rtc.store(
+            ((rtc_in_freq as u64 * 256) / (conf.div_int as u64 * 256 + conf.div_frac as u64)) as u16,
+            Ordering::Relaxed,
+        );
     } else {
         peris.set_rtc(false);
+        CLOCKS.rtc.store(0, Ordering::Relaxed);
     }
 
     // Peripheral clocks should now all be running
     reset::unreset_wait(peris);
 }
 
-unsafe fn configure_rosc(config: RoscConfig) {
+unsafe fn configure_rosc(config: RoscConfig) -> u32 {
     let p = pac::ROSC;
 
     p.freqa().write(|w| {
@@ -436,193 +553,55 @@ unsafe fn configure_rosc(config: RoscConfig) {
         w.set_enable(pac::rosc::vals::Enable::ENABLE);
         w.set_freq_range(pac::rosc::vals::FreqRange(config.range as u16));
     });
-}
 
-pub fn estimate_rosc_freq() -> u32 {
-    let p = pac::ROSC;
-
-    let base = match unsafe { p.ctrl().read().freq_range() } {
-        pac::rosc::vals::FreqRange::LOW => 84_000_000,
-        pac::rosc::vals::FreqRange::MEDIUM => 104_000_000,
-        pac::rosc::vals::FreqRange::HIGH => 140_000_000,
-        pac::rosc::vals::FreqRange::TOOHIGH => 208_000_000,
-        _ => unreachable!(),
-    };
-    let mut div = unsafe { p.div().read().0 - pac::rosc::vals::Div::PASS.0 as u32 };
-    if div == 0 {
-        div = 32
-    }
+    config.hz
+}
 
-    base / div
+pub fn rosc_freq() -> u32 {
+    CLOCKS.rosc.load(Ordering::Relaxed)
 }
 
 pub fn xosc_freq() -> u32 {
-    unsafe { XIN_HZ }
+    CLOCKS.xosc.load(Ordering::Relaxed)
 }
 
 pub fn gpin0_freq() -> u32 {
-    todo!()
+    CLOCKS.gpin0.load(Ordering::Relaxed)
 }
 pub fn gpin1_freq() -> u32 {
-    todo!()
+    CLOCKS.gpin1.load(Ordering::Relaxed)
 }
 
 pub fn pll_sys_freq() -> u32 {
-    let p = pac::PLL_SYS;
-
-    let input_freq = xosc_freq();
-    let cs = unsafe { p.cs().read() };
-
-    let refdiv = cs.refdiv() as u32;
-    let fbdiv = unsafe { p.fbdiv_int().read().fbdiv_int() } as u32;
-    let (postdiv1, postdiv2) = unsafe {
-        let prim = p.prim().read();
-        (prim.postdiv1() as u32, prim.postdiv2() as u32)
-    };
-
-    (((input_freq / refdiv) * fbdiv) / postdiv1) / postdiv2
+    CLOCKS.pll_sys.load(Ordering::Relaxed)
 }
 
 pub fn pll_usb_freq() -> u32 {
-    let p = pac::PLL_USB;
-
-    let input_freq = xosc_freq();
-    let cs = unsafe { p.cs().read() };
-
-    let refdiv = cs.refdiv() as u32;
-    let fbdiv = unsafe { p.fbdiv_int().read().fbdiv_int() } as u32;
-    let (postdiv1, postdiv2) = unsafe {
-        let prim = p.prim().read();
-        (prim.postdiv1() as u32, prim.postdiv2() as u32)
-    };
-
-    (((input_freq / refdiv) * fbdiv) / postdiv1) / postdiv2
+    CLOCKS.pll_usb.load(Ordering::Relaxed)
 }
 
 pub fn clk_sys_freq() -> u32 {
-    let c = pac::CLOCKS;
-    let ctrl = unsafe { c.clk_sys_ctrl().read() };
-
-    let base = match ctrl.src() {
-        ClkSysCtrlSrc::CLK_REF => clk_ref_freq(),
-        ClkSysCtrlSrc::CLKSRC_CLK_SYS_AUX => match ctrl.auxsrc() {
-            ClkSysCtrlAuxsrc::CLKSRC_PLL_SYS => pll_sys_freq(),
-            ClkSysCtrlAuxsrc::CLKSRC_PLL_USB => pll_usb_freq(),
-            ClkSysCtrlAuxsrc::ROSC_CLKSRC => estimate_rosc_freq(),
-            ClkSysCtrlAuxsrc::XOSC_CLKSRC => xosc_freq(),
-            ClkSysCtrlAuxsrc::CLKSRC_GPIN0 => gpin0_freq(),
-            ClkSysCtrlAuxsrc::CLKSRC_GPIN1 => gpin1_freq(),
-            _ => unreachable!(),
-        },
-        _ => unreachable!(),
-    };
-
-    let div = unsafe { c.clk_sys_div().read() };
-    let int = if div.int() == 0 { 65536 } else { div.int() };
-    // TODO handle fractional clock div
-    let _frac = div.frac();
-
-    base / int
+    CLOCKS.sys.load(Ordering::Relaxed)
 }
 
 pub fn clk_ref_freq() -> u32 {
-    let c = pac::CLOCKS;
-    let ctrl = unsafe { c.clk_ref_ctrl().read() };
-
-    let base = match ctrl.src() {
-        ClkRefCtrlSrc::ROSC_CLKSRC_PH => estimate_rosc_freq(),
-        ClkRefCtrlSrc::XOSC_CLKSRC => xosc_freq(),
-        ClkRefCtrlSrc::CLKSRC_CLK_REF_AUX => match ctrl.auxsrc() {
-            ClkRefCtrlAuxsrc::CLKSRC_PLL_USB => pll_usb_freq(),
-            ClkRefCtrlAuxsrc::CLKSRC_GPIN0 => gpin0_freq(),
-            ClkRefCtrlAuxsrc::CLKSRC_GPIN1 => gpin1_freq(),
-            _ => unreachable!(),
-        },
-        _ => unreachable!(),
-    };
-
-    let div = unsafe { c.clk_ref_div().read() };
-    let int = if div.int() == 0 { 4 } else { div.int() as u32 };
-
-    base / int
+    CLOCKS.reference.load(Ordering::Relaxed)
 }
 
 pub fn clk_peri_freq() -> u32 {
-    let c = pac::CLOCKS;
-    let src = unsafe { c.clk_peri_ctrl().read().auxsrc() };
-
-    match src {
-        ClkPeriCtrlAuxsrc::CLK_SYS => clk_sys_freq(),
-        ClkPeriCtrlAuxsrc::CLKSRC_PLL_SYS => pll_sys_freq(),
-        ClkPeriCtrlAuxsrc::CLKSRC_PLL_USB => pll_usb_freq(),
-        ClkPeriCtrlAuxsrc::ROSC_CLKSRC_PH => estimate_rosc_freq(),
-        ClkPeriCtrlAuxsrc::XOSC_CLKSRC => xosc_freq(),
-        ClkPeriCtrlAuxsrc::CLKSRC_GPIN0 => gpin0_freq(),
-        ClkPeriCtrlAuxsrc::CLKSRC_GPIN1 => gpin1_freq(),
-        _ => unreachable!(),
-    }
+    CLOCKS.peri.load(Ordering::Relaxed)
 }
 
 pub fn clk_usb_freq() -> u32 {
-    let c = pac::CLOCKS;
-    let ctrl = unsafe { c.clk_usb_ctrl().read() };
-
-    let base = match ctrl.auxsrc() {
-        ClkUsbCtrlAuxsrc::CLKSRC_PLL_SYS => pll_sys_freq(),
-        ClkUsbCtrlAuxsrc::CLKSRC_PLL_USB => pll_usb_freq(),
-        ClkUsbCtrlAuxsrc::ROSC_CLKSRC_PH => estimate_rosc_freq(),
-        ClkUsbCtrlAuxsrc::XOSC_CLKSRC => xosc_freq(),
-        ClkUsbCtrlAuxsrc::CLKSRC_GPIN0 => gpin0_freq(),
-        ClkUsbCtrlAuxsrc::CLKSRC_GPIN1 => gpin1_freq(),
-        _ => unreachable!(),
-    };
-
-    let div = unsafe { c.clk_ref_div().read() };
-    let int = if div.int() == 0 { 4 } else { div.int() as u32 };
-
-    base / int
+    CLOCKS.usb.load(Ordering::Relaxed)
 }
 
 pub fn clk_adc_freq() -> u32 {
-    let c = pac::CLOCKS;
-    let ctrl = unsafe { c.clk_adc_ctrl().read() };
-
-    let base = match ctrl.auxsrc() {
-        ClkAdcCtrlAuxsrc::CLKSRC_PLL_SYS => pll_sys_freq(),
-        ClkAdcCtrlAuxsrc::CLKSRC_PLL_USB => pll_usb_freq(),
-        ClkAdcCtrlAuxsrc::ROSC_CLKSRC_PH => estimate_rosc_freq(),
-        ClkAdcCtrlAuxsrc::XOSC_CLKSRC => xosc_freq(),
-        ClkAdcCtrlAuxsrc::CLKSRC_GPIN0 => gpin0_freq(),
-        ClkAdcCtrlAuxsrc::CLKSRC_GPIN1 => gpin1_freq(),
-        _ => unreachable!(),
-    };
-
-    let div = unsafe { c.clk_adc_div().read() };
-    let int = if div.int() == 0 { 4 } else { div.int() as u32 };
-
-    base / int
+    CLOCKS.adc.load(Ordering::Relaxed)
 }
 
-pub fn clk_rtc_freq() -> u32 {
-    let c = pac::CLOCKS;
-    let src = unsafe { c.clk_rtc_ctrl().read().auxsrc() };
-
-    let base = match src {
-        ClkRtcCtrlAuxsrc::CLKSRC_PLL_USB => pll_usb_freq(),
-        ClkRtcCtrlAuxsrc::CLKSRC_PLL_SYS => pll_sys_freq(),
-        ClkRtcCtrlAuxsrc::ROSC_CLKSRC_PH => estimate_rosc_freq(),
-        ClkRtcCtrlAuxsrc::XOSC_CLKSRC => xosc_freq(),
-        ClkRtcCtrlAuxsrc::CLKSRC_GPIN0 => gpin0_freq(),
-        ClkRtcCtrlAuxsrc::CLKSRC_GPIN1 => gpin1_freq(),
-        _ => unreachable!(),
-    };
-
-    let div = unsafe { c.clk_rtc_div().read() };
-    let int = if div.int() == 0 { 65536 } else { div.int() };
-    // TODO handle fractional clock div
-    let _frac = div.frac();
-
-    base / int
+pub fn clk_rtc_freq() -> u16 {
+    CLOCKS.rtc.load(Ordering::Relaxed)
 }
 
 unsafe fn start_xosc(crystal_hz: u32) {
@@ -640,14 +619,15 @@ unsafe fn start_xosc(crystal_hz: u32) {
 }
 
 #[inline(always)]
-unsafe fn configure_pll(p: pac::pll::Pll, input_freq: u32, config: PllConfig) {
-    let ref_freq = input_freq / config.refdiv;
-
+unsafe fn configure_pll(p: pac::pll::Pll, input_freq: u32, config: PllConfig) -> u32 {
+    let ref_freq = input_freq / config.refdiv as u32;
     assert!(config.fbdiv >= 16 && config.fbdiv <= 320);
     assert!(config.post_div1 >= 1 && config.post_div1 <= 7);
     assert!(config.post_div2 >= 1 && config.post_div2 <= 7);
-    assert!(config.post_div2 <= config.post_div1);
+    assert!(config.refdiv >= 1 && config.refdiv <= 63);
     assert!(ref_freq >= 5_000_000 && ref_freq <= 800_000_000);
+    let vco_freq = ref_freq.saturating_mul(config.fbdiv as u32);
+    assert!(vco_freq >= 750_000_000 && vco_freq <= 1800_000_000);
 
     // Load VCO-related dividers before starting VCO
     p.cs().write(|w| w.set_refdiv(config.refdiv as _));
@@ -671,6 +651,8 @@ unsafe fn configure_pll(p: pac::pll::Pll, input_freq: u32, config: PllConfig) {
 
     // Turn on post divider
     p.pwr().modify(|w| w.set_postdivpd(false));
+
+    vco_freq / ((config.post_div1 * config.post_div2) as u32)
 }
 
 pub trait GpinPin: crate::gpio::Pin {
@@ -812,12 +794,12 @@ impl<'d, T: GpoutPin> Gpout<'d, T> {
             ClkGpoutCtrlAuxsrc::CLKSRC_GPIN0 => gpin0_freq(),
             ClkGpoutCtrlAuxsrc::CLKSRC_GPIN1 => gpin1_freq(),
             ClkGpoutCtrlAuxsrc::CLKSRC_PLL_USB => pll_usb_freq(),
-            ClkGpoutCtrlAuxsrc::ROSC_CLKSRC => estimate_rosc_freq(),
+            ClkGpoutCtrlAuxsrc::ROSC_CLKSRC => rosc_freq(),
             ClkGpoutCtrlAuxsrc::XOSC_CLKSRC => xosc_freq(),
             ClkGpoutCtrlAuxsrc::CLK_SYS => clk_sys_freq(),
             ClkGpoutCtrlAuxsrc::CLK_USB => clk_usb_freq(),
             ClkGpoutCtrlAuxsrc::CLK_ADC => clk_adc_freq(),
-            ClkGpoutCtrlAuxsrc::CLK_RTC => clk_rtc_freq(),
+            ClkGpoutCtrlAuxsrc::CLK_RTC => clk_rtc_freq() as _,
             ClkGpoutCtrlAuxsrc::CLK_REF => clk_ref_freq(),
             _ => unreachable!(),
         };
diff --git a/embassy-rp/src/rtc/mod.rs b/embassy-rp/src/rtc/mod.rs
index c173909c7..c213ad174 100644
--- a/embassy-rp/src/rtc/mod.rs
+++ b/embassy-rp/src/rtc/mod.rs
@@ -26,12 +26,7 @@ impl<'d, T: Instance> RealTimeClock<'d, T> {
         into_ref!(inner);
 
         // Set the RTC divider
-        unsafe {
-            inner
-                .regs()
-                .clkdiv_m1()
-                .write(|w| w.set_clkdiv_m1(clk_rtc_freq() as u16 - 1))
-        };
+        unsafe { inner.regs().clkdiv_m1().write(|w| w.set_clkdiv_m1(clk_rtc_freq() - 1)) };
 
         let mut result = Self { inner };
         result.set_leap_year_check(true); // should be on by default, make sure this is the case.