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[v1,2/2] i2c: tegra: Synchronize DMA before termination

Message ID 20200319201140.17451-3-digetx@gmail.com
State Superseded
Headers show
Series NVIDIA Tegra I2C synchronization correction | expand

Commit Message

Dmitry Osipenko March 19, 2020, 8:11 p.m. UTC 
DMA transfer could be completed, but CPU (which handles DMA interrupt)
may get too busy and can't handle the interrupt in a timely manner,
despite of DMA IRQ being raised. In this case the DMA state needs to
synchronized before terminating DMA transfer in order not to miss the
DMA transfer completion.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/i2c/busses/i2c-tegra.c | 9 +++++++++
 1 file changed, 9 insertions(+)
diff mbox series

Patch

diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index dabb9223990c..b69a10497cd5 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -1224,6 +1224,15 @@  static int tegra_i2c_xfer_msg(struct tegra_i2c_dev *i2c_dev,
 		time_left = tegra_i2c_wait_completion_timeout(
 				i2c_dev, &i2c_dev->dma_complete, xfer_time);
 
+		/*
+		 * Synchronize DMA first, since dmaengine_terminate_sync()
+		 * performs synchronization after the transfer's termination
+		 * and we want to get a completion if transfer succeeded.
+		 */
+		dmaengine_synchronize(i2c_dev->msg_read ?
+				      i2c_dev->rx_dma_chan :
+				      i2c_dev->tx_dma_chan);
+
 		dmaengine_terminate_sync(i2c_dev->msg_read ?
 					 i2c_dev->rx_dma_chan :
 					 i2c_dev->tx_dma_chan);