Merge #714

714: add more clock options for l4 and l5 r=Dirbaio a=ant32

- added an assert so it panics if pll48div is not 48Mhz
- added MSI as a clock source for PLL
- removed hsi48 option for MCUs mentioned in l4 rcc presentation
- copied some code from l4 to l5, but don't have a way of testing it.

Co-authored-by: Philip A Reimer <antreimer@gmail.com>

embassy-stm32/src/rcc/l4.rs

@@ -96,6 +96,7 @@ pub enum APBPrescaler {
 pub enum PLLSource {
     HSI16,
     HSE(Hertz),
+    MSI(MSIRange),
 }
 
 seq_macro::seq!(N in 8..=86 {
@@ -192,6 +193,7 @@ impl From<PLLSource> for Pllsrc {
         match val {
             PLLSource::HSI16 => Pllsrc::HSI16,
             PLLSource::HSE(_) => Pllsrc::HSE,
+            PLLSource::MSI(_) => Pllsrc::MSI,
         }
     }
 }
@@ -275,6 +277,7 @@ pub struct Config {
         Option<PLLSAI1QDiv>,
         Option<PLLSAI1PDiv>,
     )>,
+    #[cfg(not(any(stm32l471, stm32l475, stm32l476, stm32l486)))]
     pub hsi48: bool,
 }
 
@@ -287,6 +290,7 @@ impl Default for Config {
             apb1_pre: APBPrescaler::NotDivided,
             apb2_pre: APBPrescaler::NotDivided,
             pllsai1: None,
+            #[cfg(not(any(stm32l471, stm32l475, stm32l476, stm32l486)))]
             hsi48: false,
         }
     }
@@ -341,6 +345,18 @@ pub(crate) unsafe fn init(config: Config) {
                     while !RCC.cr().read().hsirdy() {}
                     HSI16_FREQ
                 }
+                PLLSource::MSI(range) => {
+                    // Enable MSI
+                    RCC.cr().write(|w| {
+                        let bits: Msirange = range.into();
+                        w.set_msirange(bits);
+                        w.set_msipllen(false); // should be turned on if LSE is started
+                        w.set_msirgsel(true);
+                        w.set_msion(true);
+                    });
+                    while !RCC.cr().read().msirdy() {}
+                    range.into()
+                }
             };
 
             // Disable PLL
@@ -366,7 +382,9 @@ pub(crate) unsafe fn init(config: Config) {
             });
 
             // Enable as clock source for USB, RNG if PLL48 divisor is provided
-            if pll48div.is_some() {
+            if let Some(pll48div) = pll48div {
+                let freq = (src_freq / prediv.to_div() * mul.to_mul()) / pll48div.to_div();
+                assert!(freq == 48_000_000);
                 RCC.ccipr().modify(|w| {
                     w.set_clk48sel(0b10);
                 });
@@ -408,6 +426,7 @@ pub(crate) unsafe fn init(config: Config) {
         }
     };
 
+    #[cfg(not(any(stm32l471, stm32l475, stm32l476, stm32l486)))]
     if config.hsi48 {
         RCC.crrcr().modify(|w| w.set_hsi48on(true));
         while !RCC.crrcr().read().hsi48rdy() {}

embassy-stm32/src/rcc/l5.rs

@@ -96,6 +96,7 @@ pub enum APBPrescaler {
 pub enum PLLSource {
     HSI16,
     HSE(Hertz),
+    MSI(MSIRange),
 }
 
 seq_macro::seq!(N in 8..=86 {
@@ -192,6 +193,7 @@ impl From<PLLSource> for Pllsrc {
         match val {
             PLLSource::HSI16 => Pllsrc::HSI16,
             PLLSource::HSE(_) => Pllsrc::HSE,
+            PLLSource::MSI(_) => Pllsrc::MSI,
         }
     }
 }
@@ -275,6 +277,7 @@ pub struct Config {
         Option<PLLSAI1QDiv>,
         Option<PLLSAI1PDiv>,
     )>,
+    pub hsi48: bool,
 }
 
 impl Default for Config {
@@ -286,6 +289,7 @@ impl Default for Config {
             apb1_pre: APBPrescaler::NotDivided,
             apb2_pre: APBPrescaler::NotDivided,
             pllsai1: None,
+            hsi48: false,
         }
     }
 }
@@ -339,6 +343,18 @@ pub(crate) unsafe fn init(config: Config) {
                     while !RCC.cr().read().hsirdy() {}
                     HSI16_FREQ
                 }
+                PLLSource::MSI(range) => {
+                    // Enable MSI
+                    RCC.cr().write(|w| {
+                        let bits: Msirange = range.into();
+                        w.set_msirange(bits);
+                        w.set_msipllen(false); // should be turned on if LSE is started
+                        w.set_msirgsel(true);
+                        w.set_msion(true);
+                    });
+                    while !RCC.cr().read().msirdy() {}
+                    range.into()
+                }
             };
 
             // Disable PLL
@@ -364,7 +380,9 @@ pub(crate) unsafe fn init(config: Config) {
             });
 
             // Enable as clock source for USB, RNG if PLL48 divisor is provided
-            if pll48div.is_some() {
+            if let Some(pll48div) = pll48div {
+                let freq = (src_freq / prediv.to_div() * mul.to_mul()) / pll48div.to_div();
+                assert!(freq == 48_000_000);
                 RCC.ccipr1().modify(|w| {
                     w.set_clk48msel(0b10);
                 });
@@ -406,6 +424,14 @@ pub(crate) unsafe fn init(config: Config) {
         }
     };
 
+    if config.hsi48 {
+        RCC.crrcr().modify(|w| w.set_hsi48on(true));
+        while !RCC.crrcr().read().hsi48rdy() {}
+
+        // Enable as clock source for USB, RNG and SDMMC
+        RCC.ccipr1().modify(|w| w.set_clk48msel(0));
+    }
+
     // Set flash wait states
     // VCORE Range 0 (performance), others TODO
     FLASH.acr().modify(|w| {

examples/stm32l4/src/bin/rng.rs

@@ -12,12 +12,13 @@ use panic_probe as _;
 
 fn config() -> Config {
     let mut config = Config::default();
+    // 72Mhz clock (16 / 1 * 18 / 4)
     config.rcc.mux = ClockSrc::PLL(
         PLLSource::HSI16,
-        PLLClkDiv::Div2,
+        PLLClkDiv::Div4,
         PLLSrcDiv::Div1,
-        PLLMul::Mul8,
-        Some(PLLClkDiv::Div2),
+        PLLMul::Mul18,
+        Some(PLLClkDiv::Div6), // 48Mhz (16 / 1 * 18 / 6)
     );
     config
 }