From: Lucas Stach <l.stach@pengutronix.de>
To: Philipp Puschmann <philipp.puschmann@emlix.com>,
linux-kernel@vger.kernel.org
Cc: festevam@gmail.com, kernel@pengutronix.de,
gregkh@linuxfoundation.org, s.hauer@pengutronix.de,
vkoul@kernel.org, linux-imx@nxp.com,
linux-serial@vger.kernel.org, jslaby@suse.com,
dmaengine@vger.kernel.org, dan.j.williams@intel.com,
shawnguo@kernel.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/4] dmaengine: imx-sdma: fix buffer ownership
Date: Mon, 16 Sep 2019 16:17:00 +0200 [thread overview]
Message-ID: <9bcf315369449a025828410396935b679aae14bf.camel@pengutronix.de> (raw)
In-Reply-To: <20190911144943.21554-2-philipp.puschmann@emlix.com>
On Mi, 2019-09-11 at 16:49 +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 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.
>
> It may be further a good idea to make the status struct member volatile or
> access it using writel or similar to rule out that the compiler sets the
> BD_DONE flag before the callback routine has finished.
>
> Signed-off-by: Philipp Puschmann <philipp.puschmann@emlix.com>
> ---
> drivers/dma/imx-sdma.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
> index a01f4b5d793c..1abb14ff394d 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 +816,8 @@ static void sdma_update_channel_loop(struct sdma_channel *sdmac)
> dmaengine_desc_get_callback_invoke(&desc->vd.tx, NULL);
> spin_lock(&sdmac->vc.lock);
To address your comment from the second paragraph of the commit message
there should be a dma_wmb() here before changing the status flag.
Regards,
Lucas
> + bd->mode.status |= BD_DONE;
> +
> if (error)
> sdmac->status = old_status;
> }
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next prev parent reply other threads:[~2019-09-16 14:17 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-11 14:49 [PATCH 0/4] Fix UART DMA freezes for iMX6 Philipp Puschmann
2019-09-11 14:49 ` [PATCH 1/4] dmaengine: imx-sdma: fix buffer ownership Philipp Puschmann
2019-09-16 14:17 ` Lucas Stach [this message]
2019-09-19 9:20 ` Philipp Puschmann
2019-09-11 14:49 ` [PATCH 2/4] dmaengine: imx-sdma: fix dma freezes Philipp Puschmann
2019-09-16 14:22 ` Lucas Stach
2019-09-11 14:49 ` [PATCH 3/4] serial: imx: adapt rx buffer and dma periods Philipp Puschmann
2019-09-16 14:24 ` Lucas Stach
2019-09-11 14:49 ` [PATCH 4/4] dmaengine: imx-sdma: drop redundant variable Philipp Puschmann
2019-09-16 14:30 ` Lucas Stach
2019-09-12 15:31 ` [PATCH 0/4] Fix UART DMA freezes for iMX6 Fabio Estevam
2019-09-12 18:23 ` Fabio Estevam
2019-09-16 13:55 ` Philipp Puschmann
2019-09-16 14:00 ` Fabio Estevam
2019-09-16 14:10 ` [EXT] " Andy Duan
2019-09-16 8:02 ` Robin Gong
2019-09-16 13:41 ` Philipp Puschmann
2019-09-19 10:23 ` [PATCH v2 0/3] Fix UART DMA freezes for i.MX SOCs Philipp Puschmann
2019-09-19 10:23 ` [PATCH v2 1/3] dmaengine: imx-sdma: fix buffer ownership Philipp Puschmann
2019-09-19 10:27 ` Lucas Stach
2019-09-19 10:34 ` Philipp Puschmann
2019-09-19 10:23 ` [PATCH v2 2/3] dmaengine: imx-sdma: fix dma freezes Philipp Puschmann
2019-09-19 10:23 ` [PATCH v2 3/3] dmaengine: imx-sdma: drop redundant variable Philipp Puschmann
2019-09-19 10:33 ` [PATCH v2 0/3] Fix UART DMA freezes for i.MX SOCs Fabio Estevam
2019-09-19 10:45 ` [PATCH v3 " Philipp Puschmann
2019-09-19 10:45 ` [PATCH v3 1/3] dmaengine: imx-sdma: fix buffer ownership Philipp Puschmann
2019-09-19 11:37 ` Fabio Estevam
2019-09-19 11:42 ` Philipp Puschmann
2019-09-19 10:45 ` [PATCH v3 2/3] dmaengine: imx-sdma: fix dma freezes Philipp Puschmann
2019-09-19 10:45 ` [PATCH v3 3/3] dmaengine: imx-sdma: drop redundant variable Philipp Puschmann
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