From 54e695b1b2105c1b2484584d100564afc0679596 Mon Sep 17 00:00:00 2001
From: pennae <github@quasiparticle.net>
Date: Tue, 2 May 2023 10:50:06 +0200
Subject: [PATCH] rp/pio: fix dma

fixing the dma word size to 32 makes it impossible to implement any
peripheral that takes its data in smaller chunks, eg uart, spi, i2c,
ws2812, the list goes on.

compiler barriers were also not set correctly; we need a SeqCst barrier
before starting a transfer as well to avoid reordering of accesses into
a buffer after dma has started.
---
 embassy-rp/src/pio.rs | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/embassy-rp/src/pio.rs b/embassy-rp/src/pio.rs
index 7faec10b5..cab57f765 100644
--- a/embassy-rp/src/pio.rs
+++ b/embassy-rp/src/pio.rs
@@ -8,10 +8,10 @@ use embassy_cortex_m::interrupt::{Interrupt, InterruptExt};
 use embassy_hal_common::PeripheralRef;
 use embassy_sync::waitqueue::AtomicWaker;
 
-use crate::dma::{Channel, Transfer};
+use crate::dma::{Channel, Transfer, Word};
 use crate::gpio::sealed::Pin as SealedPin;
 use crate::gpio::{Drive, Pin, Pull, SlewRate};
-use crate::pac::dma::vals::{DataSize, TreqSel};
+use crate::pac::dma::vals::TreqSel;
 use crate::pio::sealed::{PioInstance as _, SmInstance as _};
 use crate::{interrupt, pac, peripherals, RegExt};
 
@@ -820,7 +820,7 @@ pub trait PioStateMachine: sealed::PioStateMachine + Sized + Unpin {
         }
     }
 
-    fn dma_push<'a, C: Channel>(&'a self, ch: PeripheralRef<'a, C>, data: &'a [u32]) -> Transfer<'a, C> {
+    fn dma_push<'a, C: Channel, W: Word>(&'a self, ch: PeripheralRef<'a, C>, data: &'a [W]) -> Transfer<'a, C> {
         unsafe {
             let pio_no = Self::Pio::PIO_NO;
             let sm_no = Self::Sm::SM_NO;
@@ -829,10 +829,11 @@ pub trait PioStateMachine: sealed::PioStateMachine + Sized + Unpin {
             p.write_addr()
                 .write_value(Self::Pio::PIO.txf(sm_no as usize).ptr() as u32);
             p.trans_count().write_value(data.len() as u32);
+            compiler_fence(Ordering::SeqCst);
             p.ctrl_trig().write(|w| {
                 // Set TX DREQ for this statemachine
                 w.set_treq_sel(TreqSel(pio_no * 8 + sm_no));
-                w.set_data_size(DataSize::SIZE_WORD);
+                w.set_data_size(W::size());
                 w.set_chain_to(ch.number());
                 w.set_incr_read(true);
                 w.set_incr_write(false);
@@ -843,7 +844,7 @@ pub trait PioStateMachine: sealed::PioStateMachine + Sized + Unpin {
         Transfer::new(ch)
     }
 
-    fn dma_pull<'a, C: Channel>(&'a self, ch: PeripheralRef<'a, C>, data: &'a mut [u32]) -> Transfer<'a, C> {
+    fn dma_pull<'a, C: Channel, W: Word>(&'a self, ch: PeripheralRef<'a, C>, data: &'a mut [W]) -> Transfer<'a, C> {
         unsafe {
             let pio_no = Self::Pio::PIO_NO;
             let sm_no = Self::Sm::SM_NO;
@@ -852,10 +853,11 @@ pub trait PioStateMachine: sealed::PioStateMachine + Sized + Unpin {
             p.read_addr()
                 .write_value(Self::Pio::PIO.rxf(sm_no as usize).ptr() as u32);
             p.trans_count().write_value(data.len() as u32);
+            compiler_fence(Ordering::SeqCst);
             p.ctrl_trig().write(|w| {
-                // Set TX DREQ for this statemachine
+                // Set RX DREQ for this statemachine
                 w.set_treq_sel(TreqSel(pio_no * 8 + sm_no + 4));
-                w.set_data_size(DataSize::SIZE_WORD);
+                w.set_data_size(W::size());
                 w.set_chain_to(ch.number());
                 w.set_incr_read(false);
                 w.set_incr_write(true);