stm32/rcc: add ClockEnableBit struct.

embassy-stm32/build.rs

@@ -7,6 +7,7 @@ use std::{env, fs};
 
 use proc_macro2::{Ident, TokenStream};
 use quote::{format_ident, quote};
+use stm32_metapac::metadata::ir::BitOffset;
 use stm32_metapac::metadata::{
     MemoryRegionKind, PeripheralRccKernelClock, PeripheralRccRegister, PeripheralRegisters, StopMode, METADATA,
 };
@@ -359,12 +360,17 @@ fn main() {
 
     // ========
     // Extract the rcc registers
+
     let rcc_registers = METADATA
         .peripherals
         .iter()
         .filter_map(|p| p.registers.as_ref())
         .find(|r| r.kind == "rcc")
         .unwrap();
+    for b in rcc_registers.ir.blocks {
+        eprintln!("{}", b.name);
+    }
+    let rcc_block = rcc_registers.ir.blocks.iter().find(|b| b.name == "Rcc").unwrap();
 
     // ========
     // Generate RccPeripheral impls
@@ -540,6 +546,29 @@ fn main() {
             let pname = format_ident!("{}", p.name);
             let en_reg = format_ident!("{}", en.register.to_ascii_lowercase());
             let set_en_field = format_ident!("set_{}", en.field.to_ascii_lowercase());
+            let en_reg_offs = rcc_block
+                .items
+                .iter()
+                .find(|i| i.name.eq_ignore_ascii_case(en.register))
+                .unwrap()
+                .byte_offset;
+            let en_reg_offs: u8 = (en_reg_offs / 4).try_into().unwrap();
+
+            let en_bit_offs = &rcc_registers
+                .ir
+                .fieldsets
+                .iter()
+                .find(|i| i.name.eq_ignore_ascii_case(en.register))
+                .unwrap()
+                .fields
+                .iter()
+                .find(|i| i.name.eq_ignore_ascii_case(en.field))
+                .unwrap()
+                .bit_offset;
+            let BitOffset::Regular(en_bit_offs) = en_bit_offs else {
+                panic!("cursed bit offset")
+            };
+            let en_bit_offs: u8 = en_bit_offs.offset.try_into().unwrap();
 
             let refcount =
                 clock_gen.force_refcount.contains(ptype) || *rcc_field_count.get(&(en.register, en.field)).unwrap() > 1;
@@ -624,6 +653,9 @@ fn main() {
                         crate::pac::RCC.#en_reg().modify(|w| w.#set_en_field(false));
                         #decr_stop_refcount
                     }
+                    fn enable_bit() -> crate::rcc::ClockEnableBit {
+                        unsafe { crate::rcc::ClockEnableBit::new(#en_reg_offs, #en_bit_offs) }
+                    }
                 }
 
                 impl crate::rcc::RccPeripheral for peripherals::#pname {}

embassy-stm32/src/rcc/mod.rs

@@ -31,6 +31,7 @@ pub use hsi48::*;
 mod _version;
 
 pub use _version::*;
+use stm32_metapac::RCC;
 
 pub use crate::_generated::{mux, Clocks};
 use crate::time::Hertz;
@@ -66,9 +67,10 @@ pub(crate) unsafe fn get_freqs() -> &'static Clocks {
 }
 
 pub(crate) trait SealedRccPeripheral {
-    fn frequency() -> crate::time::Hertz;
+    fn frequency() -> Hertz;
     fn enable_and_reset_with_cs(cs: CriticalSection);
     fn disable_with_cs(cs: CriticalSection);
+    fn enable_bit() -> ClockEnableBit;
 
     fn enable_and_reset() {
         critical_section::with(|cs| Self::enable_and_reset_with_cs(cs))
@@ -137,3 +139,49 @@ pub unsafe fn enable_and_reset<T: RccPeripheral>() {
 pub unsafe fn disable<T: RccPeripheral>() {
     T::disable();
 }
+
+/// Struct representing some clock enable bit (xxxENR.xxEN), only known at runtime.
+#[derive(Clone, Copy)]
+pub(crate) struct ClockEnableBit {
+    /// offset in 32bit words of the xxxENR register into the RCC register block.
+    offset: u8,
+    /// bit within the register (0..=31)
+    bit: u8,
+}
+
+impl ClockEnableBit {
+    /// Safety: offset+bit must correspond to a valid xxxEN bit.
+    pub(crate) unsafe fn new(offset: u8, bit: u8) -> Self {
+        Self { offset, bit }
+    }
+
+    fn ptr(self) -> *mut u32 {
+        unsafe { (RCC.as_ptr() as *mut u32).add(self.offset as _) }
+    }
+
+    #[allow(unused)]
+    pub(crate) fn enable_with_cs(self, _cs: CriticalSection) {
+        let p = self.ptr();
+        unsafe {
+            let val = p.read_volatile();
+            p.write_volatile(val | 1u32 << self.bit);
+        }
+    }
+
+    pub(crate) fn disable_with_cs(self, _cs: CriticalSection) {
+        let p = self.ptr();
+        unsafe {
+            let val = p.read_volatile();
+            p.write_volatile(val & !(1u32 << self.bit));
+        }
+    }
+
+    #[allow(unused)]
+    pub(crate) fn enable(self) {
+        critical_section::with(|cs| self.enable_with_cs(cs))
+    }
+
+    pub(crate) fn disable(self) {
+        critical_section::with(|cs| self.disable_with_cs(cs))
+    }
+}