linux-kernel - Re: [PATCH] dmaengine: stm32-mdma: correct desc prep when channel running

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Message-ID: <ZS0aREGECQ7G+fry@matsya>
Date:   Mon, 16 Oct 2023 16:41:00 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Amelie Delaunay <amelie.delaunay@...s.st.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        M'boumba Cedric Madianga <cedric.madianga@...il.com>,
        Pierre-Yves MORDRET <pierre-yves.mordret@...com>,
        stable@...r.kernel.org, dmaengine@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dmaengine: stm32-mdma: correct desc prep when channel
 running

On 09-10-23, 11:02, Alain Volmat wrote:
> Hi Amélie,
> 
> thanks a lot.
> 
> Tested-by: Alain Volmat <alain.volmat@...s.st.com>

Please **do ** not ** top post!

> 
> Regards,
> Alain
> 
> On Mon, Oct 09, 2023 at 10:24:50AM +0200, Amelie Delaunay wrote:
> > From: Alain Volmat <alain.volmat@...s.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@...s.st.com>
> > Signed-off-by: Amelie Delaunay <amelie.delaunay@...s.st.com>
> > Cc: stable@...r.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
> > 

-- 
~Vinod