boot/stm32: autodetect thumbv6, remove cargo feature.

embassy-boot/stm32/Cargo.toml

@@ -27,7 +27,6 @@ defmt = [
     "embassy-stm32/defmt",
 ]
 debug = ["defmt-rtt"]
-thumbv6 = []
 
 [profile.dev]
 debug = 2

embassy-boot/stm32/build.rs

@@ -24,4 +24,9 @@ fn main() {
     if env::var("CARGO_FEATURE_DEFMT").is_ok() {
         println!("cargo:rustc-link-arg-bins=-Tdefmt.x");
     }
+
+    let target = env::var("TARGET").unwrap();
+    if target.starts_with("thumbv6m-") {
+        println!("cargo:rustc-cfg=armv6m");
+    }
 }

embassy-boot/stm32/src/lib.rs

@@ -76,7 +76,7 @@ impl<const PAGE_SIZE: usize> BootLoader<PAGE_SIZE> {
         trace!("Loading app at 0x{:x}", start);
         #[allow(unused_mut)]
         let mut p = cortex_m::Peripherals::steal();
-        #[cfg(not(feature = "thumbv6"))]
+        #[cfg(not(armv6m))]
         p.SCB.invalidate_icache();
         p.SCB.vtor.write(start as u32);
 

examples/boot/stm32l0/Cargo.toml

@@ -7,7 +7,7 @@ version = "0.1.0"
 [dependencies]
 embassy = { version = "0.1.0", path = "../../../embassy", features = ["nightly"] }
 embassy-stm32 = { version = "0.1.0", path = "../../../embassy-stm32", features = ["unstable-traits", "nightly", "stm32l072cz", "time-driver-any", "exti", "memory-x"]  }
-embassy-boot-stm32 = { version = "0.1.0", path = "../../../embassy-boot/stm32", features = ["thumbv6"] }
+embassy-boot-stm32 = { version = "0.1.0", path = "../../../embassy-boot/stm32" }
 embassy-embedded-hal = { version = "0.1.0", path = "../../../embassy-embedded-hal" }
 
 defmt = { version = "0.3", optional = true }

examples/boot/stm32l0/README.md

@@ -15,7 +15,7 @@ application.
 
 ```
 # Flash bootloader
-cargo flash --manifest-path ../../../embassy-boot/stm32/Cargo.toml --release --features embassy-stm32/stm32l072cz,thumbv6 --chip STM32L072CZTx
+cargo flash --manifest-path ../../../embassy-boot/stm32/Cargo.toml --release --features embassy-stm32/stm32l072cz --chip STM32L072CZTx
 # Build 'b'
 cargo build --release --bin b
 # Generate binary for 'b'