From 1d49b3444f2bd3e049f19a72da63804192ee0402 Mon Sep 17 00:00:00 2001
From: Mathias <mk@blackbird.online>
Date: Thu, 18 Aug 2022 21:09:50 +0200
Subject: [PATCH] Add DMA read + write functions

---
 embassy-rp/src/dma.rs  | 48 +++++++++++++++++++++++++++++++++++-------
 embassy-rp/src/uart.rs |  4 ++--
 2 files changed, 42 insertions(+), 10 deletions(-)

diff --git a/embassy-rp/src/dma.rs b/embassy-rp/src/dma.rs
index 531ed8020..cfaa6dd34 100644
--- a/embassy-rp/src/dma.rs
+++ b/embassy-rp/src/dma.rs
@@ -5,26 +5,45 @@ use core::task::{Context, Poll, Waker};
 use embassy_hal_common::{impl_peripheral, into_ref, Peripheral, PeripheralRef};
 use embassy_util::waitqueue::AtomicWaker;
 use futures::Future;
+use pac::dma::vals::DataSize;
 
 use crate::pac::dma::vals;
 use crate::{pac, peripherals};
 
-pub fn copy<'a, C: Channel, W: Word>(ch: impl Peripheral<P = C> + 'a, from: &[W], to: &mut [W]) -> Transfer<'a, C> {
-    assert!(from.len() == to.len());
+pub(crate) fn read<'a, C: Channel, W: Word>(ch: impl Peripheral<P = C> + 'a, from: *const W, to: *mut [W]) -> Transfer<'a, C> {
+    let (ptr, len) = crate::dma::slice_ptr_parts_mut(to);
+    copy(ch, from as *const u32, ptr as *mut u32, len, W::size())
+}
 
+pub(crate) fn write<'a, C: Channel, W: Word>(
+    ch: impl Peripheral<P = C> + 'a,
+    from: *const [W],
+    to: *mut W,
+) -> Transfer<'a, C> {
+    let (from_ptr, len) = crate::dma::slice_ptr_parts(from);
+    copy(ch, from_ptr as *const u32, to as *mut u32, len, W::size())
+}
+
+fn copy<'a, C: Channel>(
+    ch: impl Peripheral<P = C> + 'a,
+    from: *const u32,
+    to: *mut u32,
+    len: usize,
+    data_size: DataSize,
+) -> Transfer<'a, C> {
     into_ref!(ch);
 
     unsafe {
         let p = ch.regs();
 
-        p.read_addr().write_value(from.as_ptr() as u32);
-        p.write_addr().write_value(to.as_mut_ptr() as u32);
-        p.trans_count().write_value(from.len() as u32);
+        p.read_addr().write_value(from as u32);
+        p.write_addr().write_value(to as u32);
+        p.trans_count().write_value(len as u32);
 
         compiler_fence(Ordering::SeqCst);
 
         p.ctrl_trig().write(|w| {
-            w.set_data_size(W::size());
+            w.set_data_size(data_size);
             w.set_incr_read(true);
             w.set_incr_write(true);
             w.set_chain_to(ch.number());
@@ -60,7 +79,7 @@ impl<'a, C: Channel> Drop for Transfer<'a, C> {
 impl<'a, C: Channel> Unpin for Transfer<'a, C> {}
 impl<'a, C: Channel> Future for Transfer<'a, C> {
     type Output = ();
-    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
         self.channel.set_waker(cx.waker());
 
         if self.channel.is_running() {
@@ -110,13 +129,15 @@ pub trait Channel: Peripheral<P = Self> + sealed::Channel + Into<AnyChannel> + S
     }
 
     fn is_running(&self) -> bool {
-        self.regs().ctrl_trig().read().en()
+        unsafe { self.regs().ctrl_trig().read().en() }
     }
 
     fn set_waker(&self, waker: &Waker) {
         STATE.channels[self.number() as usize].waker.register(waker);
     }
 
+    fn on_irq() {}
+
     fn degrade(self) -> AnyChannel {
         AnyChannel { number: self.number() }
     }
@@ -177,6 +198,17 @@ macro_rules! channel {
     };
 }
 
+// TODO: replace transmutes with core::ptr::metadata once it's stable
+#[allow(unused)]
+pub(crate) fn slice_ptr_parts<T>(slice: *const [T]) -> (usize, usize) {
+    unsafe { core::mem::transmute(slice) }
+}
+
+#[allow(unused)]
+pub(crate) fn slice_ptr_parts_mut<T>(slice: *mut [T]) -> (usize, usize) {
+    unsafe { core::mem::transmute(slice) }
+}
+
 channel!(DMA_CH0, 0);
 channel!(DMA_CH1, 1);
 channel!(DMA_CH2, 2);
diff --git a/embassy-rp/src/uart.rs b/embassy-rp/src/uart.rs
index c1596960f..09cadf030 100644
--- a/embassy-rp/src/uart.rs
+++ b/embassy-rp/src/uart.rs
@@ -128,7 +128,7 @@ impl<'d, T: Instance> UartTx<'d, T, Async> {
             }
             // If we don't assign future to a variable, the data register pointer
             // is held across an await and makes the future non-Send.
-            let transfer = crate::dma::copy(ch, buffer, unsafe { T::regs().uartdr().ptr() });
+            let transfer = crate::dma::write(ch, buffer, T::regs().uartdr().ptr() as *mut _);
             transfer.await;
         }
         Ok(())
@@ -178,7 +178,7 @@ impl<'d, T: Instance> UartRx<'d, T, Async> {
             }
             // If we don't assign future to a variable, the data register pointer
             // is held across an await and makes the future non-Send.
-            let transfer = crate::dma::copy(ch, unsafe { T::regs().uartdr().ptr() }, buffer);
+            let transfer = crate::dma::read(ch, T::regs().uartdr().ptr() as *const _, buffer);
             transfer.await;
         }
         Ok(())