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From: Lucas Stach <l.stach@pengutronix.de>
To: Philipp Puschmann <philipp.puschmann@emlix.com>,
	 linux-kernel@vger.kernel.org
Cc: fugang.duan@nxp.com, festevam@gmail.com, s.hauer@pengutronix.de,
	vkoul@kernel.org, linux-imx@nxp.com, kernel@pengutronix.de,
	dmaengine@vger.kernel.org, dan.j.williams@intel.com,
	yibin.gong@nxp.com, shawnguo@kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 1/3] dmaengine: imx-sdma: fix buffer ownership
Date: Thu, 19 Sep 2019 12:27:58 +0200
Message-ID: <7d694da8ffe098c6c8f6fe9c3a2306fda55eb655.camel@pengutronix.de> (raw)
In-Reply-To: <20190919102319.23368-2-philipp.puschmann@emlix.com>

Hi Philipp,

On Do, 2019-09-19 at 12:23 +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.
> 
> Signed-off-by: Philipp Puschmann <philipp.puschmann@emlix.com>
> 
> ---
> 
> 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..e029a2443cfc 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_wb();

Has this change been tested? The function you want here is called
dma_wmb().

Regards,
Lucas

> +		bd->mode.status |= BD_DONE;
> +
>  		if (error)
>  			sdmac->status = old_status;
>  	}


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  reply index

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
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 [this message]
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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