2023-07-25 12:24:10

by Vijaya Krishna Nivarthi

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

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 <[email protected]>
---
drivers/spi/spi-qcom-qspi.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

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");
--
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2023-07-25 18:36:44

by Doug Anderson

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

Hi,

On Tue, Jul 25, 2023 at 4:48 AM Vijaya Krishna Nivarthi
<[email protected]> 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 <[email protected]>
> ---
> 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 <[email protected]>