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Date:   Mon, 9 Oct 2023 11:02:13 +0200
From:   Alain Volmat <alain.volmat@foss.st.com>
To:     Amelie Delaunay <amelie.delaunay@foss.st.com>
CC:     Vinod Koul <vkoul@kernel.org>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        Alexandre Torgue <alexandre.torgue@foss.st.com>,
        M'boumba Cedric Madianga <cedric.madianga@gmail.com>,
        Pierre-Yves MORDRET <pierre-yves.mordret@st.com>,
        <stable@vger.kernel.org>, <dmaengine@vger.kernel.org>,
        <linux-stm32@st-md-mailman.stormreply.com>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] dmaengine: stm32-mdma: correct desc prep when channel
 running
Message-ID: <20231009090213.GA1547647@gnbcxd0016.gnb.st.com>
Mail-Followup-To: Amelie Delaunay <amelie.delaunay@foss.st.com>,
        Vinod Koul <vkoul@kernel.org>,
        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        Alexandre Torgue <alexandre.torgue@foss.st.com>,
        M'boumba Cedric Madianga <cedric.madianga@gmail.com>,
        Pierre-Yves MORDRET <pierre-yves.mordret@st.com>,
        stable@vger.kernel.org, dmaengine@vger.kernel.org,
        linux-stm32@st-md-mailman.stormreply.com,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
References: <20231009082450.452877-1-amelie.delaunay@foss.st.com>
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Hi Am?lie,

thanks a lot.

Tested-by: Alain Volmat <alain.volmat@foss.st.com>

Regards,
Alain

On Mon, Oct 09, 2023 at 10:24:50AM +0200, Amelie Delaunay wrote:
> From: Alain Volmat <alain.volmat@foss.st.com>
> 
> In case of the prep descriptor while the channel is already running, the
> CCR register value stored into the channel could already have its EN bit
> set.  This would lead to a bad transfer since, at start transfer time,
> enabling the channel while other registers aren't yet properly set.
> To avoid this, ensure to mask the CCR_EN bit when storing the ccr value
> into the mdma channel structure.
> 
> Fixes: a4ffb13c8946 ("dmaengine: Add STM32 MDMA driver")
> Signed-off-by: Alain Volmat <alain.volmat@foss.st.com>
> Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
> Cc: stable@vger.kernel.org
> ---
>  drivers/dma/stm32-mdma.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/dma/stm32-mdma.c b/drivers/dma/stm32-mdma.c
> index bae08b3f55c7..f414efdbd809 100644
> --- a/drivers/dma/stm32-mdma.c
> +++ b/drivers/dma/stm32-mdma.c
> @@ -489,7 +489,7 @@ static int stm32_mdma_set_xfer_param(struct stm32_mdma_chan *chan,
>  	src_maxburst = chan->dma_config.src_maxburst;
>  	dst_maxburst = chan->dma_config.dst_maxburst;
>  
> -	ccr = stm32_mdma_read(dmadev, STM32_MDMA_CCR(chan->id));
> +	ccr = stm32_mdma_read(dmadev, STM32_MDMA_CCR(chan->id)) & ~STM32_MDMA_CCR_EN;
>  	ctcr = stm32_mdma_read(dmadev, STM32_MDMA_CTCR(chan->id));
>  	ctbr = stm32_mdma_read(dmadev, STM32_MDMA_CTBR(chan->id));
>  
> @@ -965,7 +965,7 @@ stm32_mdma_prep_dma_memcpy(struct dma_chan *c, dma_addr_t dest, dma_addr_t src,
>  	if (!desc)
>  		return NULL;
>  
> -	ccr = stm32_mdma_read(dmadev, STM32_MDMA_CCR(chan->id));
> +	ccr = stm32_mdma_read(dmadev, STM32_MDMA_CCR(chan->id)) & ~STM32_MDMA_CCR_EN;
>  	ctcr = stm32_mdma_read(dmadev, STM32_MDMA_CTCR(chan->id));
>  	ctbr = stm32_mdma_read(dmadev, STM32_MDMA_CTBR(chan->id));
>  	cbndtr = stm32_mdma_read(dmadev, STM32_MDMA_CBNDTR(chan->id));
> -- 
> 2.25.1
>