STM32F0/F3 Remap DMA channels

Fixes #3643

3 files changed, 32 insertions, 2 deletions

diff --git a/embassy-stm32/CHANGELOG.md b/embassy-stm32/CHANGELOG.md
index b6781905e..c4c2cd013 100644
--- a/embassy-stm32/CHANGELOG.md
+++ b/embassy-stm32/CHANGELOG.md
@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## Unreleased
 - Modify BufferedUart initialization to take pins before interrupts ([#3983](https://github.com/embassy-rs/embassy/pull/3983))
 - Added a 'single-bank' and a 'dual-bank' feature so chips with configurable flash bank setups are be supported in embassy ([#4125](https://github.com/embassy-rs/embassy/pull/4125))
+- Add automatic setting of remap bits when using alternate DMA channels on STM32F0 and STM32F3 devices ([#3653](https://github.com/embassy-rs/embassy/pull/3653))
 
 ## 0.2.0 - 2025-01-10
 
diff --git a/embassy-stm32/build.rs b/embassy-stm32/build.rs
index 753f241c7..068dadf4b 100644
--- a/embassy-stm32/build.rs
+++ b/embassy-stm32/build.rs
@@ -1551,9 +1551,26 @@ fn main() {
                             quote!(())
                         };
 
+                        let mut remap = quote!();
+                        for remap_info in ch.remap {
+                            let peripheral = format_ident!("{}", remap_info.peripheral);
+                            let register = format_ident!("{}", remap_info.register.to_lowercase());
+                            let setter = format_ident!("set_{}", remap_info.field.to_lowercase());
+
+                            let value = if remap_info.value.contains("true") || remap_info.value.contains("false") {
+                                let value = format_ident!("{}", remap_info.value);
+                                quote!(#value)
+                            } else {
+                                let value = remap_info.value.parse::<u8>().unwrap();
+                                quote!(#value.into())
+                            };
+
+                            remap.extend(quote!(crate::pac::#peripheral.#register().modify(|w| w.#setter(#value));));
+                        }
+
                         let channel = format_ident!("{}", channel);
                         g.extend(quote! {
-                            dma_trait_impl!(#tr, #peri, #channel, #request);
+                            dma_trait_impl!(#tr, #peri, #channel, #request, {#remap});
                         });
                     }
                 }
diff --git a/embassy-stm32/src/macros.rs b/embassy-stm32/src/macros.rs
index 7526bb180..3a0b490ba 100644
--- a/embassy-stm32/src/macros.rs
+++ b/embassy-stm32/src/macros.rs
@@ -81,17 +81,28 @@ macro_rules! dma_trait {
             /// Note: in some chips, ST calls this the "channel", and calls channels "streams".
             /// `embassy-stm32` always uses the "channel" and "request number" names.
             fn request(&self) -> crate::dma::Request;
+            #[doc = "Remap the DMA channel"]
+            fn remap(&self);
         }
     };
 }
 
 #[allow(unused)]
 macro_rules! dma_trait_impl {
-    (crate::$mod:ident::$trait:ident$(<$mode:ident>)?, $instance:ident, $channel:ident, $request:expr) => {
+    (crate::$mod:ident::$trait:ident$(<$mode:ident>)?, $instance:ident, $channel:ident, $request:expr, $remap:expr) => {
         impl crate::$mod::$trait<crate::peripherals::$instance $(, crate::$mod::$mode)?> for crate::peripherals::$channel {
             fn request(&self) -> crate::dma::Request {
                 $request
             }
+
+            fn remap(&self) {
+                critical_section::with(|_| {
+                    #[allow(unused_unsafe)]
+                    unsafe {
+                        $remap;
+                    }
+                });
+            }
         }
     };
 }
@@ -111,6 +122,7 @@ macro_rules! new_dma_nonopt {
 macro_rules! new_dma {
     ($name:ident) => {{
         let dma = $name;
+        dma.remap();
         let request = dma.request();
         Some(crate::dma::ChannelAndRequest {
             channel: dma.into(),