rp/multicore: enable fpu on second core only if building for -eabihf …

…targets.

embassy-rp/build.rs

@@ -15,5 +15,24 @@ fn main() {
 
         println!("cargo:rerun-if-changed=build.rs");
         println!("cargo:rerun-if-changed=link-rp.x.in");
+
+        // code below taken from https://github.com/rust-embedded/cortex-m/blob/master/cortex-m-rt/build.rs
+
+        let mut target = env::var("TARGET").unwrap();
+
+        // When using a custom target JSON, `$TARGET` contains the path to that JSON file. By
+        // convention, these files are named after the actual target triple, eg.
+        // `thumbv7m-customos-elf.json`, so we extract the file stem here to allow custom target specs.
+        let path = Path::new(&target);
+        if path.extension() == Some(OsStr::new("json")) {
+            target = path
+                .file_stem()
+                .map_or(target.clone(), |stem| stem.to_str().unwrap().to_string());
+        }
+
+        println!("cargo:rustc-check-cfg=cfg(has_fpu)");
+        if target.ends_with("-eabihf") {
+            println!("cargo:rustc-cfg=has_fpu");
+        }
     }
 }

embassy-rp/src/multicore.rs

@@ -170,7 +170,7 @@ where
         };
 
         // Enable FPU
-        #[cfg(feature = "_rp235x")]
+        #[cfg(all(feature = "_rp235x", has_fpu))]
         unsafe {
             let p = cortex_m::Peripherals::steal();
             p.SCB.cpacr.modify(|cpacr| cpacr | (3 << 20) | (3 << 22));