Enable timer clock in RCC on timer start

* Moves the tim2-specific code into macro which always uses TIM2
* For peripherals without clock specified, attempt to locate enable and
  reset registers in the RCC block matching the peripheral name. This
  could be useful for peripherals where deducing the clock name might
  not be feasible, but it remains to be tested with more chip families
  to see if it is sufficiently accurate.

embassy-macros/src/chip/stm32.rs

@@ -16,7 +16,10 @@ pub fn generate(embassy_prefix: &ModulePrefix, config: syn::Expr) -> TokenStream
             interrupt::take!(TIM2),
         );
         let clock = unsafe { make_static(&mut c) };
-        clock.start_tim2();
+
+        // TODO: Is TIM2 always APB1?
+        let timer_freq = unsafe { #embassy_stm32_path::rcc::get_freqs().apb1_clk };
+        clock.start(timer_freq);
 
         let mut alarm = clock.alarm1();
         unsafe { #embassy_path::time::set_clock(clock) };

embassy-stm32/src/clock.rs

@@ -11,6 +11,7 @@ use embassy::time::{Clock as EmbassyClock, TICKS_PER_SECOND};
 use crate::interrupt::{CriticalSection, Interrupt, Mutex};
 use crate::pac::timer::TimGp16;
 use crate::peripherals;
+use crate::rcc::RccPeripheral;
 use crate::time::Hertz;
 
 // Clock timekeeping works with something we call "periods", which are time intervals
@@ -76,27 +77,12 @@ impl<T: Instance> Clock<T> {
         }
     }
 
-    // TODO: Temporary until clock code generation is in place
-    pub fn start_tim2(&'static self) {
-        cfg_if::cfg_if! {
-            if #[cfg(rcc_l0)] {
-                unsafe {
-                    let rcc = crate::pac::RCC;
-                    rcc.apb1enr()
-                        .modify(|w| w.set_tim2en(true));
-                    rcc.apb1rstr().modify(|w| w.set_tim2rst(true));
-                    rcc.apb1rstr().modify(|w| w.set_tim2rst(false));
-                }
-
-                let timer_freq = unsafe { crate::rcc::get_freqs().apb1_clk };
-                self.start(timer_freq);
-            }
-        }
-    }
-
     pub fn start(&'static self, timer_freq: Hertz) {
         let inner = T::inner();
 
+        T::enable();
+        T::reset();
+
         // NOTE(unsafe) Critical section to use the unsafe methods
         critical_section::with(|_| {
             unsafe {
@@ -359,7 +345,7 @@ pub(crate) mod sealed {
     }
 }
 
-pub trait Instance: sealed::Instance + Sized + 'static {}
+pub trait Instance: sealed::Instance + Sized + RccPeripheral + 'static {}
 
 macro_rules! impl_timer {
     ($inst:ident) => {

stm32-metapac/gen/src/lib.rs

@@ -267,12 +267,23 @@ pub fn gen(options: Options) {
                     _ => {}
                 }
 
-                if let Some(clock) = &p.clock {
                 if let Some(rcc) = &rcc {
                     // Workaround for clock registers being split on some chip families. Assume fields are
                     // named after peripheral and look for first field matching and use that register.
-                        let en = find_reg_for_field(&rcc, clock, &format!("{}EN", name));
+                    //
-                        let rst = find_reg_for_field(&rcc, clock, &format!("{}RST", name));
+                    // Not all peripherals have the clock hint due to insufficient information from
+                    // chip definition. If clock is not specified, the first matching register with the
+                    // expected field will be used.
+                    let en = find_reg_for_field(
+                        &rcc,
+                        p.clock.as_ref().unwrap_or(&String::new()),
+                        &format!("{}EN", name),
+                    );
+                    let rst = find_reg_for_field(
+                        &rcc,
+                        p.clock.as_ref().unwrap_or(&String::new()),
+                        &format!("{}RST", name),
+                    );
 
                     match (en, rst) {
                         (Some((enable_reg, enable_field)), Some((reset_reg, reset_field))) => {
@@ -296,7 +307,6 @@ pub fn gen(options: Options) {
                     }
                 }
             }
-            }
 
             dev.peripherals.push(ir_peri);
         }