From e36ae76e4518465953cf1adfb5c40f8cd91667d6 Mon Sep 17 00:00:00 2001
From: Bob McWhirter <bmcwhirt@redhat.com>
Date: Tue, 24 Aug 2021 14:44:31 -0400
Subject: [PATCH] Fix blocking-write for SPI.

---
 embassy-stm32/src/spi/v3.rs | 30 +++++++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/embassy-stm32/src/spi/v3.rs b/embassy-stm32/src/spi/v3.rs
index cfee54da..dd8c1c2f 100644
--- a/embassy-stm32/src/spi/v3.rs
+++ b/embassy-stm32/src/spi/v3.rs
@@ -171,6 +171,7 @@ impl<'d, T: Instance, Tx, Rx> Spi<'d, T, Tx, Rx> {
                 w.set_dsize(word_size.dsize());
             });
             T::regs().cr1().modify(|w| {
+                w.set_csusp(false);
                 w.set_spe(true);
             });
         }
@@ -375,8 +376,19 @@ impl<'d, T: Instance> embedded_hal::blocking::spi::Write<u8> for Spi<'d, T, NoDm
                 }
                 if !sr.txp() {
                     // loop waiting for TXE
+                    continue;
                 }
+                break;
             }
+            unsafe {
+                let rxdr = regs.rxdr().ptr() as *const u8;
+                // discard read to prevent pverrun.
+                let _ = ptr::read_volatile(rxdr);
+            }
+        }
+
+        while unsafe { !regs.sr().read().txc() } {
+            // spin
         }
 
         Ok(())
@@ -469,8 +481,20 @@ impl<'d, T: Instance> embedded_hal::blocking::spi::Write<u16> for Spi<'d, T, NoD
                 }
                 if !sr.txp() {
                     // loop waiting for TXE
+                    continue;
                 }
+                break;
             }
+
+            unsafe {
+                let rxdr = regs.rxdr().ptr() as *const u8;
+                // discard read to prevent pverrun.
+                let _ = ptr::read_volatile(rxdr);
+            }
+        }
+
+        while unsafe { !regs.sr().read().txc() } {
+            // spin
         }
 
         Ok(())
@@ -537,7 +561,7 @@ impl<'d, T: Instance, Tx, Rx> traits::Spi<u8> for Spi<'d, T, Tx, Rx> {
 
 impl<'d, T: Instance, Tx: TxDmaChannel<T>, Rx> traits::Write<u8> for Spi<'d, T, Tx, Rx> {
     #[rustfmt::skip]
-    type WriteFuture<'a> where Self: 'a = impl Future<Output = Result<(), Self::Error>> + 'a;
+    type WriteFuture<'a> where Self: 'a = impl Future<Output=Result<(), Self::Error>> + 'a;
 
     fn write<'a>(&'a mut self, data: &'a [u8]) -> Self::WriteFuture<'a> {
         self.write_dma_u8(data)
@@ -548,7 +572,7 @@ impl<'d, T: Instance, Tx: TxDmaChannel<T>, Rx: RxDmaChannel<T>> traits::Read<u8>
     for Spi<'d, T, Tx, Rx>
 {
     #[rustfmt::skip]
-    type ReadFuture<'a> where Self: 'a = impl Future<Output = Result<(), Self::Error>> + 'a;
+    type ReadFuture<'a> where Self: 'a = impl Future<Output=Result<(), Self::Error>> + 'a;
 
     fn read<'a>(&'a mut self, data: &'a mut [u8]) -> Self::ReadFuture<'a> {
         self.read_dma_u8(data)
@@ -559,7 +583,7 @@ impl<'d, T: Instance, Tx: TxDmaChannel<T>, Rx: RxDmaChannel<T>> traits::FullDupl
     for Spi<'d, T, Tx, Rx>
 {
     #[rustfmt::skip]
-    type WriteReadFuture<'a> where Self: 'a = impl Future<Output = Result<(), Self::Error>> + 'a;
+    type WriteReadFuture<'a> where Self: 'a = impl Future<Output=Result<(), Self::Error>> + 'a;
 
     fn read_write<'a>(
         &'a mut self,