stm32/dma: impl. wringbuf for bdma

2 files changed, 155 insertions, 3 deletions

diff --git a/embassy-stm32/src/dma/bdma.rs b/embassy-stm32/src/dma/bdma.rs
index 7b5008f07..2905338de 100644
--- a/embassy-stm32/src/dma/bdma.rs
+++ b/embassy-stm32/src/dma/bdma.rs
@@ -9,7 +9,7 @@ use atomic_polyfill::AtomicUsize;
 use embassy_hal_internal::{into_ref, Peripheral, PeripheralRef};
 use embassy_sync::waitqueue::AtomicWaker;
 
-use super::ringbuffer::{DmaCtrl, OverrunError, ReadableDmaRingBuffer};
+use super::ringbuffer::{DmaCtrl, OverrunError, ReadableDmaRingBuffer, WritableDmaRingBuffer};
 use super::word::{Word, WordSize};
 use super::Dir;
 use crate::_generated::BDMA_CHANNEL_COUNT;
@@ -559,3 +559,155 @@ impl<'a, C: Channel, W: Word> Drop for ReadableRingBuffer<'a, C, W> {
         fence(Ordering::SeqCst);
     }
 }
+
+pub struct WritableRingBuffer<'a, C: Channel, W: Word> {
+    cr: regs::Cr,
+    channel: PeripheralRef<'a, C>,
+    ringbuf: WritableDmaRingBuffer<'a, W>,
+}
+
+impl<'a, C: Channel, W: Word> WritableRingBuffer<'a, C, W> {
+    pub unsafe fn new_write(
+        channel: impl Peripheral<P = C> + 'a,
+        _request: Request,
+        peri_addr: *mut W,
+        buffer: &'a mut [W],
+        _options: TransferOptions,
+    ) -> Self {
+        into_ref!(channel);
+
+        let len = buffer.len();
+        assert!(len > 0 && len <= 0xFFFF);
+
+        let dir = Dir::MemoryToPeripheral;
+        let data_size = W::size();
+
+        let channel_number = channel.num();
+        let dma = channel.regs();
+
+        // "Preceding reads and writes cannot be moved past subsequent writes."
+        fence(Ordering::SeqCst);
+
+        #[cfg(bdma_v2)]
+        critical_section::with(|_| channel.regs().cselr().modify(|w| w.set_cs(channel.num(), _request)));
+
+        let mut w = regs::Cr(0);
+        w.set_psize(data_size.into());
+        w.set_msize(data_size.into());
+        w.set_minc(vals::Inc::ENABLED);
+        w.set_dir(dir.into());
+        w.set_teie(true);
+        w.set_htie(true);
+        w.set_tcie(true);
+        w.set_circ(vals::Circ::ENABLED);
+        w.set_pl(vals::Pl::VERYHIGH);
+        w.set_en(true);
+
+        let buffer_ptr = buffer.as_mut_ptr();
+        let mut this = Self {
+            channel,
+            cr: w,
+            ringbuf: WritableDmaRingBuffer::new(buffer),
+        };
+        this.clear_irqs();
+
+        #[cfg(dmamux)]
+        super::dmamux::configure_dmamux(&mut *this.channel, _request);
+
+        let ch = dma.ch(channel_number);
+        ch.par().write_value(peri_addr as u32);
+        ch.mar().write_value(buffer_ptr as u32);
+        ch.ndtr().write(|w| w.set_ndt(len as u16));
+
+        this
+    }
+
+    pub fn start(&mut self) {
+        let ch = self.channel.regs().ch(self.channel.num());
+        ch.cr().write_value(self.cr)
+    }
+
+    pub fn clear(&mut self) {
+        self.ringbuf.clear(DmaCtrlImpl(self.channel.reborrow()));
+    }
+
+    /// Write elements from the ring buffer
+    /// Return a tuple of the length written and the length remaining in the buffer
+    pub fn read(&mut self, buf: &[W]) -> Result<(usize, usize), OverrunError> {
+        self.ringbuf.write(DmaCtrlImpl(self.channel.reborrow()), buf)
+    }
+
+    /// Write an exact number of elements to the ringbuffer.
+    pub async fn write_exact(&mut self, buffer: &[W]) -> Result<usize, OverrunError> {
+        use core::future::poll_fn;
+        use core::sync::atomic::compiler_fence;
+
+        let mut written_data = 0;
+        let buffer_len = buffer.len();
+
+        poll_fn(|cx| {
+            self.set_waker(cx.waker());
+
+            compiler_fence(Ordering::SeqCst);
+
+            match self.read(&buffer[written_data..buffer_len]) {
+                Ok((len, remaining)) => {
+                    written_data += len;
+                    if written_data == buffer_len {
+                        Poll::Ready(Ok(remaining))
+                    } else {
+                        Poll::Pending
+                    }
+                }
+                Err(e) => Poll::Ready(Err(e)),
+            }
+        })
+        .await
+    }
+
+    /// The capacity of the ringbuffer.
+    pub fn cap(&self) -> usize {
+        self.ringbuf.cap()
+    }
+
+    pub fn set_waker(&mut self, waker: &Waker) {
+        STATE.ch_wakers[self.channel.index()].register(waker);
+    }
+
+    fn clear_irqs(&mut self) {
+        let dma = self.channel.regs();
+        dma.ifcr().write(|w| {
+            w.set_htif(self.channel.num(), true);
+            w.set_tcif(self.channel.num(), true);
+            w.set_teif(self.channel.num(), true);
+        });
+    }
+
+    pub fn request_stop(&mut self) {
+        let ch = self.channel.regs().ch(self.channel.num());
+
+        // Disable the channel. Keep the IEs enabled so the irqs still fire.
+        // If the channel is enabled and transfer is not completed, we need to perform
+        // two separate write access to the CR register to disable the channel.
+        ch.cr().write(|w| {
+            w.set_teie(true);
+            w.set_htie(true);
+            w.set_tcie(true);
+        });
+    }
+
+    pub fn is_running(&mut self) -> bool {
+        let ch = self.channel.regs().ch(self.channel.num());
+        ch.cr().read().en()
+    }
+}
+
+impl<'a, C: Channel, W: Word> Drop for WritableRingBuffer<'a, C, W> {
+    fn drop(&mut self) {
+        self.request_stop();
+        while self.is_running() {}
+
+        // "Subsequent reads and writes cannot be moved ahead of preceding reads."
+        fence(Ordering::SeqCst);
+    }
+}
diff --git a/embassy-stm32/src/dma/dma.rs b/embassy-stm32/src/dma/dma.rs
index 3c5c79fd8..9cd7aa8d5 100644
--- a/embassy-stm32/src/dma/dma.rs
+++ b/embassy-stm32/src/dma/dma.rs
@@ -814,7 +814,7 @@ pub struct WritableRingBuffer<'a, C: Channel, W: Word> {
 }
 
 impl<'a, C: Channel, W: Word> WritableRingBuffer<'a, C, W> {
-    pub unsafe fn new_read(
+    pub unsafe fn new_write(
         channel: impl Peripheral<P = C> + 'a,
         _request: Request,
         peri_addr: *mut W,
@@ -899,7 +899,7 @@ impl<'a, C: Channel, W: Word> WritableRingBuffer<'a, C, W> {
         self.ringbuf.write(DmaCtrlImpl(self.channel.reborrow()), buf)
     }
 
-    /// Write an exact number of elements from the ringbuffer.
+    /// Write an exact number of elements to the ringbuffer.
     pub async fn write_exact(&mut self, buffer: &[W]) -> Result<usize, OverrunError> {
         use core::future::poll_fn;
         use core::sync::atomic::compiler_fence;