2 files changed, 10 insertions, 4 deletions

diff --git a/embassy-stm32/src/rcc/c0.rs b/embassy-stm32/src/rcc/c0.rs
index 04cbe83ed..4ec8e7780 100644
--- a/embassy-stm32/src/rcc/c0.rs
+++ b/embassy-stm32/src/rcc/c0.rs
@@ -3,6 +3,7 @@ pub use crate::pac::rcc::vals::{
     Hpre as AHBPrescaler, Hsidiv as HsiSysDiv, Hsikerdiv as HsiKerDiv, Ppre as APBPrescaler, Sw as Sysclk,
 };
 use crate::pac::{FLASH, RCC};
+use crate::rcc::LSI_FREQ;
 use crate::time::Hertz;
 
 /// HSI speed
@@ -121,9 +122,13 @@ pub(crate) unsafe fn init(config: Config) {
         }
     };
 
+    let rtc = config.ls.init();
+
     let sys = match config.sys {
         Sysclk::HSISYS => unwrap!(hsisys),
         Sysclk::HSE => unwrap!(hse),
+        Sysclk::LSI => { assert!(config.ls.lsi); LSI_FREQ }
+        Sysclk::LSE => unwrap!(config.ls.lse).frequency,
         _ => unreachable!(),
     };
 
@@ -162,8 +167,6 @@ pub(crate) unsafe fn init(config: Config) {
         RCC.cr().modify(|w| w.set_hsion(false));
     }
 
-    let rtc = config.ls.init();
-
     config.mux.init();
 
     set_clocks!(
diff --git a/embassy-stm32/src/rcc/g0.rs b/embassy-stm32/src/rcc/g0.rs
index f55b18290..c84ac5166 100644
--- a/embassy-stm32/src/rcc/g0.rs
+++ b/embassy-stm32/src/rcc/g0.rs
@@ -5,6 +5,7 @@ pub use crate::pac::rcc::vals::{
     Pllr as PllRDiv, Pllsrc as PllSource, Ppre as APBPrescaler, Sw as Sysclk,
 };
 use crate::pac::{FLASH, PWR, RCC};
+use crate::rcc::LSI_FREQ;
 use crate::time::Hertz;
 
 /// HSI speed
@@ -234,10 +235,14 @@ pub(crate) unsafe fn init(config: Config) {
         })
         .unwrap_or_default();
 
+    let rtc = config.ls.init();
+
     let sys = match config.sys {
         Sysclk::HSI => unwrap!(hsisys),
         Sysclk::HSE => unwrap!(hse),
         Sysclk::PLL1_R => unwrap!(pll.pll_r),
+        Sysclk::LSI => { assert!(config.ls.lsi); LSI_FREQ }
+        Sysclk::LSE => unwrap!(config.ls.lse).frequency,
         _ => unreachable!(),
     };
 
@@ -286,8 +291,6 @@ pub(crate) unsafe fn init(config: Config) {
         PWR.cr1().modify(|w| w.set_lpr(true));
     }
 
-    let rtc = config.ls.init();
-
     config.mux.init();
 
     set_clocks!(