diff mbox series

[v2,2/2] i2c: tegra: Synchronize DMA before termination

Message ID 20200324191217.1829-3-digetx@gmail.com
State New
Headers show
Series NVIDIA Tegra I2C synchronization correction | expand

Commit Message

Dmitry Osipenko March 24, 2020, 7:12 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(+)

Comments

Wolfram Sang April 15, 2020, 4:31 p.m. UTC | #1
On Tue, Mar 24, 2020 at 10:12:17PM +0300, Dmitry Osipenko wrote:
> 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>

Applied to for-current, thanks!
diff mbox series

Patch

diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
index 0daa863fb26f..0c6dac770fc3 100644
--- a/drivers/i2c/busses/i2c-tegra.c
+++ b/drivers/i2c/busses/i2c-tegra.c
@@ -1223,6 +1223,15 @@  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);