allow selecting any clock source when freezing rcc configuration

src/can.rs

@@ -11,19 +11,6 @@ mod sealed {
     pub trait Rx<CAN> {}
 }
 
-/// Select an FDCAN Clock Source
-#[allow(clippy::upper_case_acronyms)]
-#[allow(dead_code)]
-enum FdCanClockSource {
-    /// Select HSE as the FDCAN clock source
-    HSE = 0b00,
-    /// Select PLL "Q" clock as the FDCAN clock source
-    PLLQ = 0b01,
-    /// Select "P" clock as the FDCAN clock source
-    PCLK = 0b10,
-    //Reserved = 0b10,
-}
-
 /// Storage type for the CAN controller
 #[derive(Debug)]
 pub struct Can<FDCAN> {
@@ -55,18 +42,6 @@ where
     {
         Self::enable(&rcc.rb);
 
-        if rcc.rb.ccipr.read().fdcansel().is_hse() {
-            // Select P clock as FDCAN clock source
-            rcc.rb.ccipr.modify(|_, w| {
-                // This is sound, as `FdCanClockSource` only contains valid values for this field.
-                unsafe {
-                    w.fdcansel().bits(FdCanClockSource::PCLK as u8);
-                }
-
-                w
-            });
-        }
-
         self.fdcan_unchecked()
     }
 

src/rcc/config.rs

@@ -325,6 +325,18 @@ impl Default for PllConfig {
     }
 }
 
+/// FDCAN Clock Source
+#[allow(clippy::upper_case_acronyms)]
+pub enum FdCanClockSource {
+    /// Select HSE as the FDCAN clock source
+    HSE = 0b00,
+    /// Select PLL "Q" clock as the FDCAN clock source
+    PLLQ = 0b01,
+    /// Select "P" clock as the FDCAN clock source
+    PCLK = 0b10,
+    //Reserved = 0b10,
+}
+
 /// Clocks configutation
 pub struct Config {
     pub(crate) sys_mux: SysClockSrc,
@@ -335,6 +347,8 @@ pub struct Config {
 
     /// Required for f_sys > 150MHz
     pub(crate) enable_boost: bool,
+
+    pub(crate) fdcansel: FdCanClockSource,
 }
 
 impl Config {
@@ -379,6 +393,11 @@ impl Config {
         self.enable_boost = enable_boost;
         self
     }
+
+    pub fn fdcan_src(mut self, mux: FdCanClockSource) -> Self {
+        self.fdcansel = mux;
+        self
+    }
 }
 
 impl Default for Config {
@@ -390,6 +409,7 @@ impl Default for Config {
             apb1_psc: Prescaler::NotDivided,
             apb2_psc: Prescaler::NotDivided,
             enable_boost: false,
+            fdcansel: FdCanClockSource::HSE,
         }
     }
 }

src/rcc/mod.rs

@@ -216,6 +216,12 @@ impl Rcc {
             _ => apb2_freq * 2,
         };
 
+        // Configure FDCAN clock source.
+        self.rb.ccipr.modify(|_, w| unsafe {
+            // This is sound, as `FdCanClockSource` only contains valid values for this field.
+            w.fdcansel().bits(rcc_cfg.fdcansel as u8)
+        });
+
         Rcc {
             rb: self.rb,
             clocks: Clocks {