From cf8235cedeb1fa82e594daa67211d55a51c67b11 Mon Sep 17 00:00:00 2001
From: Robin Mueller <robin.mueller.m@gmail.com>
Date: Fri, 4 Jun 2021 12:58:30 +0200
Subject: [PATCH] solves issue with DMA

---
 stm32h7/devicetest/GyroL3GD20H.cpp | 16 ++++++++++++++--
 stm32h7/devicetest/GyroL3GD20H.h   |  4 +++-
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/stm32h7/devicetest/GyroL3GD20H.cpp b/stm32h7/devicetest/GyroL3GD20H.cpp
index 7c02e22..bf11081 100644
--- a/stm32h7/devicetest/GyroL3GD20H.cpp
+++ b/stm32h7/devicetest/GyroL3GD20H.cpp
@@ -11,7 +11,10 @@
 #include "stm32h7xx_hal_spi.h"
 #include "stm32h7xx_hal_rcc.h"
 
-std::array<uint8_t, GyroL3GD20H::recvBufferSize> GyroL3GD20H::rxBuffer;
+alignas(32) std::array<uint8_t, GyroL3GD20H::recvBufferSize> GyroL3GD20H::rxBuffer;
+alignas(32) std::array<uint8_t, GyroL3GD20H::txBufferSize>
+        GyroL3GD20H::txBuffer __attribute__((section(".dma_buffer")));
+
 TransferStates transferState = TransferStates::IDLE;
 DMA_HandleTypeDef txDmaHandle;
 DMA_HandleTypeDef rxDmaHandle;
@@ -83,6 +86,15 @@ ReturnValue_t GyroL3GD20H::performOperation() {
 }
 
 ReturnValue_t GyroL3GD20H::handleDmaTransfer() {
+    /* Clean D-cache */
+    /* Make sure the address is 32-byte aligned and add 32-bytes to length,
+    in case it overlaps cacheline */
+    // See https://community.st.com/s/article/FAQ-DMA-is-not-working-on-STM32H7-devices
+#if STM_USE_PERIPHERAL_TX_BUFFER_MPU_PROTECTION == 0
+    SCB_CleanDCache_by_Addr((uint32_t*)(((uint32_t)txBuffer.data()) & ~(uint32_t)0x1F),
+            txBuffer.size()+32);
+#endif
+
     if(HAL_SPI_TransmitReceive_DMA(spiHandle, txBuffer.data(), rxBuffer.data(), 2) != HAL_OK) {
         // Transfer error in transmission process
         sif::printWarning("Error transmitting SPI with DMA\n");
@@ -90,7 +102,7 @@ ReturnValue_t GyroL3GD20H::handleDmaTransfer() {
 
     // Wait for the transfer to complete
     while (transferState == TransferStates::WAIT) {
-        //TaskFactory::delayTask(1);
+        TaskFactory::delayTask(1);
     }
 
     // Invalidate cache prior to access by CPU
diff --git a/stm32h7/devicetest/GyroL3GD20H.h b/stm32h7/devicetest/GyroL3GD20H.h
index ed2d9a2..59c39b9 100644
--- a/stm32h7/devicetest/GyroL3GD20H.h
+++ b/stm32h7/devicetest/GyroL3GD20H.h
@@ -33,8 +33,10 @@ private:
     SPI_HandleTypeDef* spiHandle;
     spi::TransferModes transferMode;
     static constexpr size_t recvBufferSize = 32 * 10;
+
     static std::array<uint8_t, recvBufferSize> rxBuffer;
-    std::array<uint8_t, 32> txBuffer;
+    static constexpr size_t txBufferSize = 32;
+    static std::array<uint8_t, txBufferSize> txBuffer;
 
     ReturnValue_t handleDmaTransfer();
     ReturnValue_t handlePollingTransfer();