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[3/4] spi: spi-qcom-qspi: Call dma_wmb() after setting up descriptors

Message ID 1690285689-30233-4-git-send-email-quic_vnivarth@quicinc.com (mailing list archive)
State Accepted
Commit cfb81f2243b25a0d79accc6510ad66c5c5ad99ba
Headers show
Series spi: spi-qcom-qspi: Follow-up patches to DMA mode support | expand

Commit Message

Vijaya Krishna Nivarthi July 25, 2023, 11:48 a.m. UTC 
After setting up dma descriptors and before initiaiting dma transfer, call
dma_wmb() to ensure all writes go through.
This doesn't fix any reported problem but is added for safety.

Signed-off-by: Vijaya Krishna Nivarthi <quic_vnivarth@quicinc.com>
---
 drivers/spi/spi-qcom-qspi.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Comments

Doug Anderson July 25, 2023, 5:58 p.m. UTC | #1 
Hi,

On Tue, Jul 25, 2023 at 4:48 AM Vijaya Krishna Nivarthi
<quic_vnivarth@quicinc.com> wrote:
>
> After setting up dma descriptors and before initiaiting dma transfer, call
> dma_wmb() to ensure all writes go through.
> This doesn't fix any reported problem but is added for safety.
>
> Signed-off-by: Vijaya Krishna Nivarthi <quic_vnivarth@quicinc.com>
> ---
>  drivers/spi/spi-qcom-qspi.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

This looks right to me.

Fixes: b5762d95607e ("spi: spi-qcom-qspi: Add DMA mode support")
Reviewed-by: Douglas Anderson <dianders@chromium.org>
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Patch

diff --git a/drivers/spi/spi-qcom-qspi.c b/drivers/spi/spi-qcom-qspi.c
index b938908..d75234d 100644
--- a/drivers/spi/spi-qcom-qspi.c
+++ b/drivers/spi/spi-qcom-qspi.c
@@ -443,8 +443,10 @@  static int qcom_qspi_transfer_one(struct spi_master *master,
 
 		ret = qcom_qspi_setup_dma_desc(ctrl, xfer);
 		if (ret != -EAGAIN) {
-			if (!ret)
+			if (!ret) {
+				dma_wmb();
 				qcom_qspi_dma_xfer(ctrl);
+			}
 			goto exit;
 		}
 		dev_warn_once(ctrl->dev, "DMA failure, falling back to PIO\n");