From 444b37fcdf744128347fd685a14874f44e5e05af Mon Sep 17 00:00:00 2001
From: Grant Miller <GrantM11235@gmail.com>
Date: Mon, 14 Mar 2022 15:10:56 -0500
Subject: [PATCH] Add `flush_rx_fifo` function

---
 embassy-stm32/src/spi/mod.rs | 13 +++++++++++++
 embassy-stm32/src/spi/v1.rs  |  8 ++++++++
 embassy-stm32/src/spi/v2.rs  | 18 ++++++++----------
 embassy-stm32/src/spi/v3.rs  | 18 ++++++++----------
 4 files changed, 37 insertions(+), 20 deletions(-)

diff --git a/embassy-stm32/src/spi/mod.rs b/embassy-stm32/src/spi/mod.rs
index 3352b24d..24efb09d 100644
--- a/embassy-stm32/src/spi/mod.rs
+++ b/embassy-stm32/src/spi/mod.rs
@@ -614,6 +614,19 @@ fn spin_until_idle(regs: Regs) {
     }
 }
 
+fn flush_rx_fifo(regs: Regs) {
+    unsafe {
+        #[cfg(not(spi_v3))]
+        while regs.sr().read().rxne() {
+            let _ = regs.dr().read();
+        }
+        #[cfg(spi_v3)]
+        while regs.sr().read().rxp() {
+            let _ = regs.rxdr().read();
+        }
+    }
+}
+
 fn finish_dma(regs: Regs) {
     spin_until_idle(regs);
 
diff --git a/embassy-stm32/src/spi/v1.rs b/embassy-stm32/src/spi/v1.rs
index 33cf9c50..19562b8a 100644
--- a/embassy-stm32/src/spi/v1.rs
+++ b/embassy-stm32/src/spi/v1.rs
@@ -17,6 +17,10 @@ impl<'d, T: Instance, Tx, Rx> Spi<'d, T, Tx, Rx> {
             });
         }
 
+        // TODO: This is unnecessary in some versions because
+        // clearing SPE automatically clears the fifos
+        flush_rx_fifo(T::regs());
+
         let tx_request = self.txdma.request();
         let tx_dst = T::regs().tx_ptr();
         unsafe { self.txdma.start_write(tx_request, write, tx_dst) }
@@ -110,6 +114,10 @@ impl<'d, T: Instance, Tx, Rx> Spi<'d, T, Tx, Rx> {
             });
         }
 
+        // TODO: This is unnecessary in some versions because
+        // clearing SPE automatically clears the fifos
+        flush_rx_fifo(T::regs());
+
         let rx_request = self.rxdma.request();
         let rx_src = T::regs().rx_ptr();
         unsafe { self.rxdma.start_read(rx_request, rx_src, read) };
diff --git a/embassy-stm32/src/spi/v2.rs b/embassy-stm32/src/spi/v2.rs
index 7ffc52be..19562b8a 100644
--- a/embassy-stm32/src/spi/v2.rs
+++ b/embassy-stm32/src/spi/v2.rs
@@ -15,13 +15,12 @@ impl<'d, T: Instance, Tx, Rx> Spi<'d, T, Tx, Rx> {
             T::regs().cr1().modify(|w| {
                 w.set_spe(false);
             });
-
-            // Flush the read buffer to avoid errornous data from being read
-            while T::regs().sr().read().rxne() {
-                let _ = T::regs().dr().read();
-            }
         }
 
+        // TODO: This is unnecessary in some versions because
+        // clearing SPE automatically clears the fifos
+        flush_rx_fifo(T::regs());
+
         let tx_request = self.txdma.request();
         let tx_dst = T::regs().tx_ptr();
         unsafe { self.txdma.start_write(tx_request, write, tx_dst) }
@@ -113,13 +112,12 @@ impl<'d, T: Instance, Tx, Rx> Spi<'d, T, Tx, Rx> {
             T::regs().cr2().modify(|reg| {
                 reg.set_rxdmaen(true);
             });
-
-            // Flush the read buffer to avoid errornous data from being read
-            while T::regs().sr().read().rxne() {
-                let _ = T::regs().dr().read();
-            }
         }
 
+        // TODO: This is unnecessary in some versions because
+        // clearing SPE automatically clears the fifos
+        flush_rx_fifo(T::regs());
+
         let rx_request = self.rxdma.request();
         let rx_src = T::regs().rx_ptr();
         unsafe { self.rxdma.start_read(rx_request, rx_src, read) };
diff --git a/embassy-stm32/src/spi/v3.rs b/embassy-stm32/src/spi/v3.rs
index 9e766cfd..5c7472cc 100644
--- a/embassy-stm32/src/spi/v3.rs
+++ b/embassy-stm32/src/spi/v3.rs
@@ -15,13 +15,12 @@ impl<'d, T: Instance, Tx, Rx> Spi<'d, T, Tx, Rx> {
             T::regs().cr1().modify(|w| {
                 w.set_spe(false);
             });
-
-            // Flush the read buffer to avoid errornous data from being read
-            while T::regs().sr().read().rxp() {
-                let _ = T::regs().rxdr().read();
-            }
         }
 
+        // TODO: This is unnecessary in some versions because
+        // clearing SPE automatically clears the fifos
+        flush_rx_fifo(T::regs());
+
         let tx_request = self.txdma.request();
         let tx_dst = T::regs().tx_ptr();
         unsafe { self.txdma.start_write(tx_request, write, tx_dst) }
@@ -119,13 +118,12 @@ impl<'d, T: Instance, Tx, Rx> Spi<'d, T, Tx, Rx> {
             T::regs().cfg1().modify(|reg| {
                 reg.set_rxdmaen(true);
             });
-
-            // Flush the read buffer to avoid errornous data from being read
-            while T::regs().sr().read().rxp() {
-                let _ = T::regs().rxdr().read();
-            }
         }
 
+        // TODO: This is unnecessary in some versions because
+        // clearing SPE automatically clears the fifos
+        flush_rx_fifo(T::regs());
+
         let rx_request = self.rxdma.request();
         let rx_src = T::regs().rx_ptr();
         unsafe { self.rxdma.start_read(rx_request, rx_src, read) };