Merge #1406

1406: rp: DMA behaviour during flash operations r=Dirbaio a=kalkyl

This PR changes the old behaviour during flash operations where all DMA transfers were paused during the flash operation.
The new approach is to wait for any DMA operating in flash region to finish and let RAM transfers continue.

Co-authored-by: kalkyl <[email protected]>

1 files changed, 5 insertions, 17 deletions

diff --git a/embassy-rp/src/flash.rs b/embassy-rp/src/flash.rs
index f2137ebe1..6ab05ff0b 100644
--- a/embassy-rp/src/flash.rs
+++ b/embassy-rp/src/flash.rs
@@ -162,8 +162,6 @@ impl<'d, T: Instance, const FLASH_SIZE: usize> Flash<'d, T, FLASH_SIZE> {
     /// - interrupts must be disabled
     /// - DMA must not access flash memory
     unsafe fn in_ram(&mut self, operation: impl FnOnce()) -> Result<(), Error> {
-        let dma_status = &mut [false; crate::dma::CHANNEL_COUNT];
-
         // Make sure we're running on CORE0
         let core_id: u32 = unsafe { pac::SIO.cpuid().read() };
         if core_id != 0 {
@@ -174,25 +172,15 @@ impl<'d, T: Instance, const FLASH_SIZE: usize> Flash<'d, T, FLASH_SIZE> {
         crate::multicore::pause_core1();
 
         critical_section::with(|_| {
-            // Pause all DMA channels for the duration of the ram operation
-            for (number, status) in dma_status.iter_mut().enumerate() {
-                let ch = crate::pac::DMA.ch(number as _);
-                *status = ch.ctrl_trig().read().en();
-                if *status {
-                    ch.ctrl_trig().modify(|w| w.set_en(false));
-                }
+            // Wait for all DMA channels in flash to finish before ram operation
+            const SRAM_LOWER: u32 = 0x2000_0000;
+            for n in 0..crate::dma::CHANNEL_COUNT {
+                let ch = crate::pac::DMA.ch(n);
+                while ch.read_addr().read() < SRAM_LOWER && ch.ctrl_trig().read().busy() {}
             }
 
             // Run our flash operation in RAM
             operation();
-
-            // Re-enable previously enabled DMA channels
-            for (number, status) in dma_status.iter().enumerate() {
-                let ch = crate::pac::DMA.ch(number as _);
-                if *status {
-                    ch.ctrl_trig().modify(|w| w.set_en(true));
-                }
-            }
         });
 
         // Resume CORE1 execution