From 0a6045367f5368256a9ab77e510fe22bd930b395 Mon Sep 17 00:00:00 2001
From: Daniel Agar <daniel@agar.ca>
Date: Mon, 30 Aug 2021 20:59:49 -0400
Subject: [PATCH] px4io_serial: ensure TX DMA is stopped if exiting early on
 stream error

 - otherwise the next retry can happen quickly enough that dma setup
hangs waiting for the stream
---
 .../nuttx/src/px4/stm/stm32f7/px4io_serial/px4io_serial.cpp     | 2 ++
 .../nuttx/src/px4/stm/stm32h7/px4io_serial/px4io_serial.cpp     | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/platforms/nuttx/src/px4/stm/stm32f7/px4io_serial/px4io_serial.cpp b/platforms/nuttx/src/px4/stm/stm32f7/px4io_serial/px4io_serial.cpp
index e9d230f7e3..20a952f421 100644
--- a/platforms/nuttx/src/px4/stm/stm32f7/px4io_serial/px4io_serial.cpp
+++ b/platforms/nuttx/src/px4/stm/stm32f7/px4io_serial/px4io_serial.cpp
@@ -328,6 +328,8 @@ ArchPX4IOSerial::_bus_exchange(IOPacket *_packet)
 		if (ret == OK) {
 			/* check for DMA errors */
 			if (_rx_dma_status & DMA_STATUS_TEIF) {
+				// stream transfer error, ensure TX DMA is also stopped before exiting early
+				stm32_dmastop(_tx_dma);
 				perf_count(_pc_dmaerrs);
 				ret = -EIO;
 				break;
diff --git a/platforms/nuttx/src/px4/stm/stm32h7/px4io_serial/px4io_serial.cpp b/platforms/nuttx/src/px4/stm/stm32h7/px4io_serial/px4io_serial.cpp
index 5743b0a3e9..36ff0b8d22 100644
--- a/platforms/nuttx/src/px4/stm/stm32h7/px4io_serial/px4io_serial.cpp
+++ b/platforms/nuttx/src/px4/stm/stm32h7/px4io_serial/px4io_serial.cpp
@@ -373,6 +373,8 @@ ArchPX4IOSerial::_bus_exchange(IOPacket *_packet)
 		if (ret == OK) {
 			/* check for DMA errors */
 			if (_rx_dma_status & DMA_STATUS_TEIF) {
+				// stream transfer error, ensure TX DMA is also stopped before exiting early
+				stm32_dmastop(_tx_dma);
 				perf_count(_pc_dmaerrs);
 				ret = -EIO;
 				break;