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SubjectRe: [PATCH v5 1/3] dmaengine: imx-sdma: fix buffer ownership
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On Mo, 2019-09-23 at 15:58 +0200, Philipp Puschmann wrote:
> BD_DONE flag marks ownership of the buffer. When 1 SDMA owns the
> buffer, when 0 ARM owns it. When processing the buffers in
> sdma_update_channel_loop the ownership of the currently processed
> buffer was set to SDMA again before running the callback function of
> the buffer and while the sdma script may be running in parallel. So
> there was the possibility to get the buffer overwritten by SDMA
> before
> it has been processed by kernel leading to kind of random errors in
> the
> upper layers, e.g. bluetooth.
>
> Fixes: 1ec1e82f2510 ("dmaengine: Add Freescale i.MX SDMA support")
> Signed-off-by: Philipp Puschmann <philipp.puschmann@emlix.com>

Reviewed-by: Lucas Stach <l.stach@pengutronix.de>

> ---
>
> Changelog v5:
> - no changes
>
> Changelog v4:
> - fixed the fixes tag
>
> Changelog v3:
> - use correct dma_wmb() instead of dma_wb()
> - add fixes tag
>
> Changelog v2:
> - add dma_wb()
>
> drivers/dma/imx-sdma.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
> index 9ba74ab7e912..b42281604e54 100644
> --- a/drivers/dma/imx-sdma.c
> +++ b/drivers/dma/imx-sdma.c
> @@ -802,7 +802,6 @@ static void sdma_update_channel_loop(struct
> sdma_channel *sdmac)
> */
>
> desc->chn_real_count = bd->mode.count;
> - bd->mode.status |= BD_DONE;
> bd->mode.count = desc->period_len;
> desc->buf_ptail = desc->buf_tail;
> desc->buf_tail = (desc->buf_tail + 1) % desc->num_bd;
> @@ -817,6 +816,9 @@ static void sdma_update_channel_loop(struct
> sdma_channel *sdmac)
> dmaengine_desc_get_callback_invoke(&desc->vd.tx, NULL);
> spin_lock(&sdmac->vc.lock);
>
> + dma_wmb();
> + bd->mode.status |= BD_DONE;
> +
> if (error)
> sdmac->status = old_status;
> }

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