Merge #1170

1170: nrf: add support for UICR configuration. r=Dirbaio a=Dirbaio

- APPROTECT enable/disable. Notably this fixes issues with nrf52-rev3 and nrf53 from locking itself at reset.
- Use NFC pins as GPIO.
- Use RESET pin as GPIO.

NFC and RESET pins singletons are made available only when usable as GPIO, for compile-time checking.

TODO: test
- [x] nrf52 rev1
- [x] nrf52 rev3
- [x] nrf53
- [x] nrf91

Co-authored-by: Dario Nieuwenhuis <[email protected]>

12 files changed, 284 insertions, 19 deletions

diff --git a/ci.sh b/ci.sh
index 4199f91d3..417937d07 100755
--- a/ci.sh
+++ b/ci.sh
@@ -46,8 +46,8 @@ cargo batch  \
     --- build --release --manifest-path embassy-nrf/Cargo.toml --target thumbv7em-none-eabi --features nightly,nrf52810,gpiote,time-driver-rtc1 \
     --- build --release --manifest-path embassy-nrf/Cargo.toml --target thumbv7em-none-eabi --features nightly,nrf52811,gpiote,time-driver-rtc1 \
     --- build --release --manifest-path embassy-nrf/Cargo.toml --target thumbv7em-none-eabi --features nightly,nrf52820,gpiote,time-driver-rtc1 \
-    --- build --release --manifest-path embassy-nrf/Cargo.toml --target thumbv7em-none-eabi --features nightly,nrf52832,gpiote,time-driver-rtc1 \
-    --- build --release --manifest-path embassy-nrf/Cargo.toml --target thumbv7em-none-eabi --features nightly,nrf52833,gpiote,time-driver-rtc1,unstable-traits \
+    --- build --release --manifest-path embassy-nrf/Cargo.toml --target thumbv7em-none-eabi --features nightly,nrf52832,gpiote,time-driver-rtc1,reset-pin-as-gpio \
+    --- build --release --manifest-path embassy-nrf/Cargo.toml --target thumbv7em-none-eabi --features nightly,nrf52833,gpiote,time-driver-rtc1,unstable-traits,nfc-pins-as-gpio \
     --- build --release --manifest-path embassy-nrf/Cargo.toml --target thumbv8m.main-none-eabihf --features nightly,nrf9160-s,gpiote,time-driver-rtc1 \
     --- build --release --manifest-path embassy-nrf/Cargo.toml --target thumbv8m.main-none-eabihf --features nightly,nrf9160-ns,gpiote,time-driver-rtc1,unstable-traits \
     --- build --release --manifest-path embassy-nrf/Cargo.toml --target thumbv8m.main-none-eabihf --features nightly,nrf5340-app-s,gpiote,time-driver-rtc1,unstable-traits \
diff --git a/embassy-nrf/Cargo.toml b/embassy-nrf/Cargo.toml
index 6b06d5d05..c31ce199b 100644
--- a/embassy-nrf/Cargo.toml
+++ b/embassy-nrf/Cargo.toml
@@ -34,22 +34,30 @@ unstable-pac = []
 # Implement embedded-hal-async traits if `nightly` is set as well.
 unstable-traits = ["embedded-hal-1"]
 
-nrf52805 = ["nrf52805-pac", "_ppi"]
-nrf52810 = ["nrf52810-pac", "_ppi"]
-nrf52811 = ["nrf52811-pac", "_ppi"]
-nrf52820 = ["nrf52820-pac", "_ppi"]
-nrf52832 = ["nrf52832-pac", "_ppi"]
-nrf52833 = ["nrf52833-pac", "_ppi", "_gpio-p1"]
-nrf52840 = ["nrf52840-pac", "_ppi", "_gpio-p1"]
-nrf5340-app-s = ["_nrf5340-app"]
-nrf5340-app-ns = ["_nrf5340-app"]
+nrf52805 = ["nrf52805-pac", "_nrf52"]
+nrf52810 = ["nrf52810-pac", "_nrf52"]
+nrf52811 = ["nrf52811-pac", "_nrf52"]
+nrf52820 = ["nrf52820-pac", "_nrf52"]
+nrf52832 = ["nrf52832-pac", "_nrf52"]
+nrf52833 = ["nrf52833-pac", "_nrf52", "_gpio-p1"]
+nrf52840 = ["nrf52840-pac", "_nrf52", "_gpio-p1"]
+nrf5340-app-s = ["_nrf5340-app", "_s"]
+nrf5340-app-ns = ["_nrf5340-app", "_ns"]
 nrf5340-net = ["_nrf5340-net"]
-nrf9160-s = ["_nrf9160"]
-nrf9160-ns = ["_nrf9160"]
+nrf9160-s = ["_nrf9160", "_s"]
+nrf9160-ns = ["_nrf9160", "_ns"]
 
 gpiote = []
 time-driver-rtc1 = ["_time-driver"]
 
+# Allow using the NFC pins as regular GPIO pins (P0_09/P0_10 on nRF52, P0_02/P0_03 on nRF53)
+nfc-pins-as-gpio = []
+
+# Allow using the RST pin as a regular GPIO pin.
+# nrf52805, nrf52810, nrf52811, nrf52832: P0_21
+# nrf52820, nrf52833, nrf52840: P0_18
+reset-pin-as-gpio = []
+
 # Features starting with `_` are for internal use only. They're not intended
 # to be enabled by other crates, and are not covered by semver guarantees.
 
@@ -57,9 +65,14 @@ _nrf5340-app = ["_nrf5340", "nrf5340-app-pac"]
 _nrf5340-net = ["_nrf5340", "nrf5340-net-pac"]
 _nrf5340 = ["_gpio-p1", "_dppi"]
 _nrf9160 = ["nrf9160-pac", "_dppi"]
+_nrf52 = ["_ppi"]
 
 _time-driver = ["dep:embassy-time", "embassy-time?/tick-hz-32_768"]
 
+# trustzone state.
+_s = []
+_ns = []
+
 _ppi = []
 _dppi = []
 _gpio-p1 = []
diff --git a/embassy-nrf/src/chips/nrf52805.rs b/embassy-nrf/src/chips/nrf52805.rs
index bf4019c13..3c74a2a63 100644
--- a/embassy-nrf/src/chips/nrf52805.rs
+++ b/embassy-nrf/src/chips/nrf52805.rs
@@ -6,6 +6,8 @@ pub const FORCE_COPY_BUFFER_SIZE: usize = 256;
 
 pub const FLASH_SIZE: usize = 192 * 1024;
 
+pub const RESET_PIN: u32 = 21;
+
 embassy_hal_common::peripherals! {
     // RTC
     RTC0,
@@ -108,6 +110,7 @@ embassy_hal_common::peripherals! {
     P0_18,
     P0_19,
     P0_20,
+    #[cfg(feature="reset-pin-as-gpio")]
     P0_21,
     P0_22,
     P0_23,
@@ -162,6 +165,7 @@ impl_pin!(P0_17, 0, 17);
 impl_pin!(P0_18, 0, 18);
 impl_pin!(P0_19, 0, 19);
 impl_pin!(P0_20, 0, 20);
+#[cfg(feature = "reset-pin-as-gpio")]
 impl_pin!(P0_21, 0, 21);
 impl_pin!(P0_22, 0, 22);
 impl_pin!(P0_23, 0, 23);
diff --git a/embassy-nrf/src/chips/nrf52810.rs b/embassy-nrf/src/chips/nrf52810.rs
index 6c28a3bea..6b5c134b8 100644
--- a/embassy-nrf/src/chips/nrf52810.rs
+++ b/embassy-nrf/src/chips/nrf52810.rs
@@ -6,6 +6,8 @@ pub const FORCE_COPY_BUFFER_SIZE: usize = 256;
 
 pub const FLASH_SIZE: usize = 192 * 1024;
 
+pub const RESET_PIN: u32 = 21;
+
 embassy_hal_common::peripherals! {
     // RTC
     RTC0,
@@ -111,6 +113,7 @@ embassy_hal_common::peripherals! {
     P0_18,
     P0_19,
     P0_20,
+    #[cfg(feature="reset-pin-as-gpio")]
     P0_21,
     P0_22,
     P0_23,
@@ -170,6 +173,7 @@ impl_pin!(P0_17, 0, 17);
 impl_pin!(P0_18, 0, 18);
 impl_pin!(P0_19, 0, 19);
 impl_pin!(P0_20, 0, 20);
+#[cfg(feature = "reset-pin-as-gpio")]
 impl_pin!(P0_21, 0, 21);
 impl_pin!(P0_22, 0, 22);
 impl_pin!(P0_23, 0, 23);
diff --git a/embassy-nrf/src/chips/nrf52811.rs b/embassy-nrf/src/chips/nrf52811.rs
index e7214cf5c..c5de9a447 100644
--- a/embassy-nrf/src/chips/nrf52811.rs
+++ b/embassy-nrf/src/chips/nrf52811.rs
@@ -6,6 +6,8 @@ pub const FORCE_COPY_BUFFER_SIZE: usize = 256;
 
 pub const FLASH_SIZE: usize = 192 * 1024;
 
+pub const RESET_PIN: u32 = 21;
+
 embassy_hal_common::peripherals! {
     // RTC
     RTC0,
@@ -111,6 +113,7 @@ embassy_hal_common::peripherals! {
     P0_18,
     P0_19,
     P0_20,
+    #[cfg(feature="reset-pin-as-gpio")]
     P0_21,
     P0_22,
     P0_23,
@@ -172,6 +175,7 @@ impl_pin!(P0_17, 0, 17);
 impl_pin!(P0_18, 0, 18);
 impl_pin!(P0_19, 0, 19);
 impl_pin!(P0_20, 0, 20);
+#[cfg(feature = "reset-pin-as-gpio")]
 impl_pin!(P0_21, 0, 21);
 impl_pin!(P0_22, 0, 22);
 impl_pin!(P0_23, 0, 23);
diff --git a/embassy-nrf/src/chips/nrf52820.rs b/embassy-nrf/src/chips/nrf52820.rs
index 21d1d16cc..81b07f32c 100644
--- a/embassy-nrf/src/chips/nrf52820.rs
+++ b/embassy-nrf/src/chips/nrf52820.rs
@@ -6,6 +6,8 @@ pub const FORCE_COPY_BUFFER_SIZE: usize = 512;
 
 pub const FLASH_SIZE: usize = 256 * 1024;
 
+pub const RESET_PIN: u32 = 18;
+
 embassy_hal_common::peripherals! {
     // USB
     USBD,
@@ -106,6 +108,7 @@ embassy_hal_common::peripherals! {
     P0_15,
     P0_16,
     P0_17,
+    #[cfg(feature="reset-pin-as-gpio")]
     P0_18,
     P0_19,
     P0_20,
@@ -168,6 +171,7 @@ impl_pin!(P0_14, 0, 14);
 impl_pin!(P0_15, 0, 15);
 impl_pin!(P0_16, 0, 16);
 impl_pin!(P0_17, 0, 17);
+#[cfg(feature = "reset-pin-as-gpio")]
 impl_pin!(P0_18, 0, 18);
 impl_pin!(P0_19, 0, 19);
 impl_pin!(P0_20, 0, 20);
diff --git a/embassy-nrf/src/chips/nrf52832.rs b/embassy-nrf/src/chips/nrf52832.rs
index 152dad4e3..c2b23fc5b 100644
--- a/embassy-nrf/src/chips/nrf52832.rs
+++ b/embassy-nrf/src/chips/nrf52832.rs
@@ -10,6 +10,8 @@ pub const FORCE_COPY_BUFFER_SIZE: usize = 255;
 // nrf52832xxAB = 256kb
 pub const FLASH_SIZE: usize = 512 * 1024;
 
+pub const RESET_PIN: u32 = 21;
+
 embassy_hal_common::peripherals! {
     // RTC
     RTC0,
@@ -109,7 +111,9 @@ embassy_hal_common::peripherals! {
     P0_06,
     P0_07,
     P0_08,
+    #[cfg(feature = "nfc-pins-as-gpio")]
     P0_09,
+    #[cfg(feature = "nfc-pins-as-gpio")]
     P0_10,
     P0_11,
     P0_12,
@@ -121,6 +125,7 @@ embassy_hal_common::peripherals! {
     P0_18,
     P0_19,
     P0_20,
+    #[cfg(feature="reset-pin-as-gpio")]
     P0_21,
     P0_22,
     P0_23,
@@ -178,7 +183,9 @@ impl_pin!(P0_05, 0, 5);
 impl_pin!(P0_06, 0, 6);
 impl_pin!(P0_07, 0, 7);
 impl_pin!(P0_08, 0, 8);
+#[cfg(feature = "nfc-pins-as-gpio")]
 impl_pin!(P0_09, 0, 9);
+#[cfg(feature = "nfc-pins-as-gpio")]
 impl_pin!(P0_10, 0, 10);
 impl_pin!(P0_11, 0, 11);
 impl_pin!(P0_12, 0, 12);
@@ -190,6 +197,7 @@ impl_pin!(P0_17, 0, 17);
 impl_pin!(P0_18, 0, 18);
 impl_pin!(P0_19, 0, 19);
 impl_pin!(P0_20, 0, 20);
+#[cfg(feature = "reset-pin-as-gpio")]
 impl_pin!(P0_21, 0, 21);
 impl_pin!(P0_22, 0, 22);
 impl_pin!(P0_23, 0, 23);
diff --git a/embassy-nrf/src/chips/nrf52833.rs b/embassy-nrf/src/chips/nrf52833.rs
index a99ca6343..95f71ade7 100644
--- a/embassy-nrf/src/chips/nrf52833.rs
+++ b/embassy-nrf/src/chips/nrf52833.rs
@@ -6,6 +6,8 @@ pub const FORCE_COPY_BUFFER_SIZE: usize = 512;
 
 pub const FLASH_SIZE: usize = 512 * 1024;
 
+pub const RESET_PIN: u32 = 18;
+
 embassy_hal_common::peripherals! {
     // USB
     USBD,
@@ -111,7 +113,9 @@ embassy_hal_common::peripherals! {
     P0_06,
     P0_07,
     P0_08,
+    #[cfg(feature = "nfc-pins-as-gpio")]
     P0_09,
+    #[cfg(feature = "nfc-pins-as-gpio")]
     P0_10,
     P0_11,
     P0_12,
@@ -120,6 +124,7 @@ embassy_hal_common::peripherals! {
     P0_15,
     P0_16,
     P0_17,
+    #[cfg(feature="reset-pin-as-gpio")]
     P0_18,
     P0_19,
     P0_20,
@@ -207,7 +212,9 @@ impl_pin!(P0_05, 0, 5);
 impl_pin!(P0_06, 0, 6);
 impl_pin!(P0_07, 0, 7);
 impl_pin!(P0_08, 0, 8);
+#[cfg(feature = "nfc-pins-as-gpio")]
 impl_pin!(P0_09, 0, 9);
+#[cfg(feature = "nfc-pins-as-gpio")]
 impl_pin!(P0_10, 0, 10);
 impl_pin!(P0_11, 0, 11);
 impl_pin!(P0_12, 0, 12);
@@ -216,6 +223,7 @@ impl_pin!(P0_14, 0, 14);
 impl_pin!(P0_15, 0, 15);
 impl_pin!(P0_16, 0, 16);
 impl_pin!(P0_17, 0, 17);
+#[cfg(feature = "reset-pin-as-gpio")]
 impl_pin!(P0_18, 0, 18);
 impl_pin!(P0_19, 0, 19);
 impl_pin!(P0_20, 0, 20);
diff --git a/embassy-nrf/src/chips/nrf52840.rs b/embassy-nrf/src/chips/nrf52840.rs
index 4f7463be2..5e7479e88 100644
--- a/embassy-nrf/src/chips/nrf52840.rs
+++ b/embassy-nrf/src/chips/nrf52840.rs
@@ -6,6 +6,8 @@ pub const FORCE_COPY_BUFFER_SIZE: usize = 512;
 
 pub const FLASH_SIZE: usize = 1024 * 1024;
 
+pub const RESET_PIN: u32 = 18;
+
 embassy_hal_common::peripherals! {
     // USB
     USBD,
@@ -117,7 +119,9 @@ embassy_hal_common::peripherals! {
     P0_06,
     P0_07,
     P0_08,
+    #[cfg(feature = "nfc-pins-as-gpio")]
     P0_09,
+    #[cfg(feature = "nfc-pins-as-gpio")]
     P0_10,
     P0_11,
     P0_12,
@@ -126,6 +130,7 @@ embassy_hal_common::peripherals! {
     P0_15,
     P0_16,
     P0_17,
+    #[cfg(feature="reset-pin-as-gpio")]
     P0_18,
     P0_19,
     P0_20,
@@ -212,7 +217,9 @@ impl_pin!(P0_05, 0, 5);
 impl_pin!(P0_06, 0, 6);
 impl_pin!(P0_07, 0, 7);
 impl_pin!(P0_08, 0, 8);
+#[cfg(feature = "nfc-pins-as-gpio")]
 impl_pin!(P0_09, 0, 9);
+#[cfg(feature = "nfc-pins-as-gpio")]
 impl_pin!(P0_10, 0, 10);
 impl_pin!(P0_11, 0, 11);
 impl_pin!(P0_12, 0, 12);
@@ -221,6 +228,7 @@ impl_pin!(P0_14, 0, 14);
 impl_pin!(P0_15, 0, 15);
 impl_pin!(P0_16, 0, 16);
 impl_pin!(P0_17, 0, 17);
+#[cfg(feature = "reset-pin-as-gpio")]
 impl_pin!(P0_18, 0, 18);
 impl_pin!(P0_19, 0, 19);
 impl_pin!(P0_20, 0, 20);
diff --git a/embassy-nrf/src/chips/nrf5340_app.rs b/embassy-nrf/src/chips/nrf5340_app.rs
index c600fcbf6..2b8b55e77 100644
--- a/embassy-nrf/src/chips/nrf5340_app.rs
+++ b/embassy-nrf/src/chips/nrf5340_app.rs
@@ -304,7 +304,9 @@ embassy_hal_common::peripherals! {
     // GPIO port 0
     P0_00,
     P0_01,
+    #[cfg(feature = "nfc-pins-as-gpio")]
     P0_02,
+    #[cfg(feature = "nfc-pins-as-gpio")]
     P0_03,
     P0_04,
     P0_05,
@@ -393,7 +395,9 @@ impl_timer!(TIMER2, TIMER2, TIMER2);
 
 impl_pin!(P0_00, 0, 0);
 impl_pin!(P0_01, 0, 1);
+#[cfg(feature = "nfc-pins-as-gpio")]
 impl_pin!(P0_02, 0, 2);
+#[cfg(feature = "nfc-pins-as-gpio")]
 impl_pin!(P0_03, 0, 3);
 impl_pin!(P0_04, 0, 4);
 impl_pin!(P0_05, 0, 5);
diff --git a/embassy-nrf/src/lib.rs b/embassy-nrf/src/lib.rs
index 20e70a248..a9683df44 100644
--- a/embassy-nrf/src/lib.rs
+++ b/embassy-nrf/src/lib.rs
@@ -24,6 +24,12 @@
 )))]
 compile_error!("No chip feature activated. You must activate exactly one of the following features: nrf52810, nrf52811, nrf52832, nrf52833, nrf52840");
 
+#[cfg(all(feature = "reset-pin-as-gpio", not(feature = "_nrf52")))]
+compile_error!("feature `reset-pin-as-gpio` is only valid for nRF52 series chips.");
+
+#[cfg(all(feature = "nfc-pins-as-gpio", not(any(feature = "_nrf52", feature = "_nrf5340-app"))))]
+compile_error!("feature `nfc-pins-as-gpio` is only valid for nRF52, or nRF53's application core.");
+
 // This mod MUST go first, so that the others see its macros.
 pub(crate) mod fmt;
 pub(crate) mod util;
@@ -139,6 +145,19 @@ pub mod config {
         ExternalFullSwing,
     }
 
+    /// SWD access port protection setting.
+    #[non_exhaustive]
+    pub enum Debug {
+        /// Debugging is allowed (APPROTECT is disabled). Default.
+        Allowed,
+        /// Debugging is not allowed (APPROTECT is enabled).
+        Disallowed,
+        /// APPROTECT is not configured (neither to enable it or disable it).
+        /// This can be useful if you're already doing it by other means and
+        /// you don't want embassy-nrf to touch UICR.
+        NotConfigured,
+    }
+
     /// Configuration for peripherals. Default configuration should work on any nRF chip.
     #[non_exhaustive]
     pub struct Config {
@@ -152,6 +171,8 @@ pub mod config {
         /// Time driver interrupt priority. Should be lower priority than softdevice if used.
         #[cfg(feature = "_time-driver")]
         pub time_interrupt_priority: crate::interrupt::Priority,
+        /// Enable or disable the debug port.
+        pub debug: Debug,
     }
 
     impl Default for Config {
@@ -166,17 +187,204 @@ pub mod config {
                 gpiote_interrupt_priority: crate::interrupt::Priority::P0,
                 #[cfg(feature = "_time-driver")]
                 time_interrupt_priority: crate::interrupt::Priority::P0,
+
+                // In NS mode, default to NotConfigured, assuming the S firmware will do it.
+                #[cfg(feature = "_ns")]
+                debug: Debug::NotConfigured,
+                #[cfg(not(feature = "_ns"))]
+                debug: Debug::Allowed,
             }
         }
     }
 }
 
+#[cfg(feature = "_nrf9160")]
+#[allow(unused)]
+mod consts {
+    pub const UICR_APPROTECT: *mut u32 = 0x00FF8000 as *mut u32;
+    pub const UICR_SECUREAPPROTECT: *mut u32 = 0x00FF802C as *mut u32;
+    pub const APPROTECT_ENABLED: u32 = 0x0000_0000;
+}
+
+#[cfg(feature = "_nrf5340-app")]
+#[allow(unused)]
+mod consts {
+    pub const UICR_APPROTECT: *mut u32 = 0x00FF8000 as *mut u32;
+    pub const UICR_SECUREAPPROTECT: *mut u32 = 0x00FF801C as *mut u32;
+    pub const UICR_NFCPINS: *mut u32 = 0x00FF8028 as *mut u32;
+    pub const APPROTECT_ENABLED: u32 = 0x0000_0000;
+    pub const APPROTECT_DISABLED: u32 = 0x50FA50FA;
+}
+
+#[cfg(feature = "_nrf5340-net")]
+#[allow(unused)]
+mod consts {
+    pub const UICR_APPROTECT: *mut u32 = 0x01FF8000 as *mut u32;
+    pub const APPROTECT_ENABLED: u32 = 0x0000_0000;
+    pub const APPROTECT_DISABLED: u32 = 0x50FA50FA;
+}
+
+#[cfg(feature = "_nrf52")]
+#[allow(unused)]
+mod consts {
+    pub const UICR_PSELRESET1: *mut u32 = 0x10001200 as *mut u32;
+    pub const UICR_PSELRESET2: *mut u32 = 0x10001204 as *mut u32;
+    pub const UICR_NFCPINS: *mut u32 = 0x1000120C as *mut u32;
+    pub const UICR_APPROTECT: *mut u32 = 0x10001208 as *mut u32;
+    pub const APPROTECT_ENABLED: u32 = 0x0000_0000;
+    pub const APPROTECT_DISABLED: u32 = 0x0000_005a;
+}
+
+#[derive(Debug, Copy, Clone, Eq, PartialEq)]
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
+enum WriteResult {
+    /// Word was written successfully, needs reset.
+    Written,
+    /// Word was already set to the value we wanted to write, nothing was done.
+    Noop,
+    /// Word is already set to something else, we couldn't write the desired value.
+    Failed,
+}
+
+unsafe fn uicr_write(address: *mut u32, value: u32) -> WriteResult {
+    let curr_val = address.read_volatile();
+    if curr_val == value {
+        return WriteResult::Noop;
+    }
+
+    // We can only change `1` bits to `0` bits.
+    if curr_val & value != value {
+        return WriteResult::Failed;
+    }
+
+    // Writing to UICR can only change `1` bits to `0` bits.
+    // If this write would change `0` bits to `1` bits, we can't do it.
+    // It is only possible to do when erasing UICR, which is forbidden if
+    // APPROTECT is enabled.
+    if (!curr_val) & value != 0 {
+        panic!("Cannot write UICR address={:08x} value={:08x}", address as u32, value)
+    }
+
+    let nvmc = &*pac::NVMC::ptr();
+    nvmc.config.write(|w| w.wen().wen());
+    while nvmc.ready.read().ready().is_busy() {}
+    address.write_volatile(value);
+    while nvmc.ready.read().ready().is_busy() {}
+    nvmc.config.reset();
+    while nvmc.ready.read().ready().is_busy() {}
+
+    WriteResult::Written
+}
+
 /// Initialize peripherals with the provided configuration. This should only be called once at startup.
 pub fn init(config: config::Config) -> Peripherals {
     // Do this first, so that it panics if user is calling `init` a second time
     // before doing anything important.
     let peripherals = Peripherals::take();
 
+    let mut needs_reset = false;
+
+    // Setup debug protection.
+    match config.debug {
+        config::Debug::Allowed => {
+            #[cfg(feature = "_nrf52")]
+            unsafe {
+                let variant = (0x1000_0104 as *mut u32).read_volatile();
+                // Get the letter for the build code (b'A' .. b'F')
+                let build_code = (variant >> 8) as u8;
+
+                if build_code >= b'F' {
+                    // Chips with build code F and higher (revision 3 and higher) have an
+                    // improved APPROTECT ("hardware and software controlled access port protection")
+                    // which needs explicit action by the firmware to keep it unlocked
+
+                    // UICR.APPROTECT = SwDisabled
+                    let res = uicr_write(consts::UICR_APPROTECT, consts::APPROTECT_DISABLED);
+                    needs_reset |= res == WriteResult::Written;
+                    // APPROTECT.DISABLE = SwDisabled
+                    (0x4000_0558 as *mut u32).write_volatile(consts::APPROTECT_DISABLED);
+                } else {
+                    // nothing to do on older chips, debug is allowed by default.
+                }
+            }
+
+            #[cfg(feature = "_nrf5340")]
+            unsafe {
+                let p = &*pac::CTRLAP::ptr();
+
+                let res = uicr_write(consts::UICR_APPROTECT, consts::APPROTECT_DISABLED);
+                needs_reset |= res == WriteResult::Written;
+                p.approtect.disable.write(|w| w.bits(consts::APPROTECT_DISABLED));
+
+                #[cfg(feature = "_nrf5340-app")]
+                {
+                    let res = uicr_write(consts::UICR_SECUREAPPROTECT, consts::APPROTECT_DISABLED);
+                    needs_reset |= res == WriteResult::Written;
+                    p.secureapprotect.disable.write(|w| w.bits(consts::APPROTECT_DISABLED));
+                }
+            }
+
+            // nothing to do on the nrf9160, debug is allowed by default.
+        }
+        config::Debug::Disallowed => unsafe {
+            // UICR.APPROTECT = Enabled
+            let res = uicr_write(consts::UICR_APPROTECT, consts::APPROTECT_ENABLED);
+            needs_reset |= res == WriteResult::Written;
+            #[cfg(any(feature = "_nrf5340-app", feature = "_nrf9160"))]
+            {
+                let res = uicr_write(consts::UICR_SECUREAPPROTECT, consts::APPROTECT_ENABLED);
+                needs_reset |= res == WriteResult::Written;
+            }
+        },
+        config::Debug::NotConfigured => {}
+    }
+
+    #[cfg(feature = "_nrf52")]
+    unsafe {
+        let value = if cfg!(feature = "reset-pin-as-gpio") {
+            !0
+        } else {
+            chip::RESET_PIN
+        };
+        let res1 = uicr_write(consts::UICR_PSELRESET1, value);
+        let res2 = uicr_write(consts::UICR_PSELRESET2, value);
+        needs_reset |= res1 == WriteResult::Written || res2 == WriteResult::Written;
+        if res1 == WriteResult::Failed || res2 == WriteResult::Failed {
+            #[cfg(not(feature = "reset-pin-as-gpio"))]
+            warn!(
+                "You have requested enabling chip reset functionality on the reset pin, by not enabling the Cargo feature `reset-pin-as-gpio`.\n\
+                However, UICR is already programmed to some other setting, and can't be changed without erasing it.\n\
+                To fix this, erase UICR manually, for example using `probe-rs-cli erase` or `nrfjprog --eraseuicr`."
+            );
+            #[cfg(feature = "reset-pin-as-gpio")]
+            warn!(
+                "You have requested using the reset pin as GPIO, by enabling the Cargo feature `reset-pin-as-gpio`.\n\
+                However, UICR is already programmed to some other setting, and can't be changed without erasing it.\n\
+                To fix this, erase UICR manually, for example using `probe-rs-cli erase` or `nrfjprog --eraseuicr`."
+            );
+        }
+    }
+
+    #[cfg(any(feature = "_nrf52", feature = "_nrf5340-app"))]
+    unsafe {
+        let value = if cfg!(feature = "nfc-pins-as-gpio") { 0 } else { !0 };
+        let res = uicr_write(consts::UICR_NFCPINS, value);
+        needs_reset |= res == WriteResult::Written;
+        if res == WriteResult::Failed {
+            // with nfc-pins-as-gpio, this can never fail because we're writing all zero bits.
+            #[cfg(not(feature = "nfc-pins-as-gpio"))]
+            warn!(
+                "You have requested to use P0.09 and P0.10 pins for NFC, by not enabling the Cargo feature `nfc-pins-as-gpio`.\n\
+                However, UICR is already programmed to some other setting, and can't be changed without erasing it.\n\
+                To fix this, erase UICR manually, for example using `probe-rs-cli erase` or `nrfjprog --eraseuicr`."
+            );
+        }
+    }
+
+    if needs_reset {
+        cortex_m::peripheral::SCB::sys_reset();
+    }
+
     let r = unsafe { &*pac::CLOCK::ptr() };
 
     // Start HFCLK.
diff --git a/embassy-nrf/src/nvmc.rs b/embassy-nrf/src/nvmc.rs
index c1ffa31aa..6f48853d5 100644
--- a/embassy-nrf/src/nvmc.rs
+++ b/embassy-nrf/src/nvmc.rs
@@ -85,23 +85,23 @@ impl<'d> Nvmc<'d> {
     }
 
     fn enable_erase(&self) {
-        #[cfg(not(any(feature = "nrf5340-app-ns", feature = "nrf9160-ns")))]
+        #[cfg(not(feature = "_ns"))]
         Self::regs().config.write(|w| w.wen().een());
-        #[cfg(any(feature = "nrf5340-app-ns", feature = "nrf9160-ns"))]
+        #[cfg(feature = "_ns")]
         Self::regs().configns.write(|w| w.wen().een());
     }
 
     fn enable_read(&self) {
-        #[cfg(not(any(feature = "nrf5340-app-ns", feature = "nrf9160-ns")))]
+        #[cfg(not(feature = "_ns"))]
         Self::regs().config.write(|w| w.wen().ren());
-        #[cfg(any(feature = "nrf5340-app-ns", feature = "nrf9160-ns"))]
+        #[cfg(feature = "_ns")]
         Self::regs().configns.write(|w| w.wen().ren());
     }
 
     fn enable_write(&self) {
-        #[cfg(not(any(feature = "nrf5340-app-ns", feature = "nrf9160-ns")))]
+        #[cfg(not(feature = "_ns"))]
         Self::regs().config.write(|w| w.wen().wen());
-        #[cfg(any(feature = "nrf5340-app-ns", feature = "nrf9160-ns"))]
+        #[cfg(feature = "_ns")]
         Self::regs().configns.write(|w| w.wen().wen());
     }
 }