Merge #1440

1440: rp: Pin fix, improve fifo handling r=Dirbaio a=CBJamo

Went to actually use this code and found two issues:
* The config for the pins got dropped in the shuffle. 
* I found that when using more than one ws2812, only the first would get data. I'm pretty sure the data was shifted out before the task got back to push the next word. So now the fifo gets filled, then we wait.

Co-authored-by: Caleb Jamison <caleb@cbjamo.com>
Co-authored-by: Caleb Jamison <caleb@hellbender.com>

examples/rp/src/bin/pio_ws2812.rs

@@ -4,18 +4,30 @@
 
 use defmt::*;
 use embassy_executor::Spawner;
+use embassy_rp::dma::{AnyChannel, Channel};
 use embassy_rp::pio::{Common, Config, FifoJoin, Instance, Pio, PioPin, ShiftConfig, ShiftDirection, StateMachine};
 use embassy_rp::relocate::RelocatedProgram;
+use embassy_rp::{clocks, into_ref, Peripheral, PeripheralRef};
 use embassy_time::{Duration, Timer};
+use fixed::types::U24F8;
 use fixed_macro::fixed;
 use smart_leds::RGB8;
 use {defmt_rtt as _, panic_probe as _};
-pub struct Ws2812<'d, P: Instance, const S: usize> {
+
+pub struct Ws2812<'d, P: Instance, const S: usize, const N: usize> {
+    dma: PeripheralRef<'d, AnyChannel>,
     sm: StateMachine<'d, P, S>,
 }
 
-impl<'d, P: Instance, const S: usize> Ws2812<'d, P, S> {
-    pub fn new(mut pio: Common<'d, P>, mut sm: StateMachine<'d, P, S>, pin: impl PioPin) -> Self {
+impl<'d, P: Instance, const S: usize, const N: usize> Ws2812<'d, P, S, N> {
+    pub fn new(
+        pio: &mut Common<'d, P>,
+        mut sm: StateMachine<'d, P, S>,
+        dma: impl Peripheral<P = impl Channel> + 'd,
+        pin: impl PioPin,
+    ) -> Self {
+        into_ref!(dma);
+
         // Setup sm0
 
         // prepare the PIO program
@@ -48,13 +60,15 @@ impl<'d, P: Instance, const S: usize> Ws2812<'d, P, S> {
 
         // Pin config
         let out_pin = pio.make_pio_pin(pin);
+        cfg.set_out_pins(&[&out_pin]);
+        cfg.set_set_pins(&[&out_pin]);
 
         let relocated = RelocatedProgram::new(&prg);
         cfg.use_program(&pio.load_program(&relocated), &[&out_pin]);
 
         // Clock config, measured in kHz to avoid overflows
         // TODO CLOCK_FREQ should come from embassy_rp
-        let clock_freq = fixed!(125_000: U24F8);
+        let clock_freq = U24F8::from_num(clocks::clk_sys_freq() / 1000);
         let ws2812_freq = fixed!(800: U24F8);
         let bit_freq = ws2812_freq * CYCLES_PER_BIT;
         cfg.clock_divider = clock_freq / bit_freq;
@@ -70,14 +84,22 @@ impl<'d, P: Instance, const S: usize> Ws2812<'d, P, S> {
         sm.set_config(&cfg);
         sm.set_enable(true);
 
-        Self { sm }
+        Self {
+            dma: dma.map_into(),
+            sm,
+        }
     }
 
-    pub async fn write(&mut self, colors: &[RGB8]) {
-        for color in colors {
-            let word = (u32::from(color.g) << 24) | (u32::from(color.r) << 16) | (u32::from(color.b) << 8);
-            self.sm.tx().wait_push(word).await;
+    pub async fn write(&mut self, colors: &[RGB8; N]) {
+        // Precompute the word bytes from the colors
+        let mut words = [0u32; N];
+        for i in 0..N {
+            let word = (u32::from(colors[i].g) << 24) | (u32::from(colors[i].r) << 16) | (u32::from(colors[i].b) << 8);
+            words[i] = word;
         }
+
+        // DMA transfer
+        self.sm.tx().dma_push(self.dma.reborrow(), &words).await;
     }
 }
 
@@ -101,7 +123,7 @@ async fn main(_spawner: Spawner) {
     info!("Start");
     let p = embassy_rp::init(Default::default());
 
-    let Pio { common, sm0, .. } = Pio::new(p.PIO0);
+    let Pio { mut common, sm0, .. } = Pio::new(p.PIO0);
 
     // This is the number of leds in the string. Helpfully, the sparkfun thing plus and adafruit
     // feather boards for the 2040 both have one built in.
@@ -110,7 +132,7 @@ async fn main(_spawner: Spawner) {
 
     // For the thing plus, use pin 8
     // For the feather, use pin 16
-    let mut ws2812 = Ws2812::new(common, sm0, p.PIN_8);
+    let mut ws2812 = Ws2812::new(&mut common, sm0, p.DMA_CH0, p.PIN_16);
 
     // Loop forever making RGB values and pushing them out to the WS2812.
     loop {