linux-kernel - Re: [PATCH 2/3] dmaengine: xilinx: xdma: Fix synchronization issue

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Date: Thu, 28 Mar 2024 01:23:13 +0100
From: Miquel Raynal <miquel.raynal@...tlin.com>
To: Lizhi Hou <lizhi.hou@....com>
Cc: Louis Chauvet <louis.chauvet@...tlin.com>, Brian Xu <brian.xu@....com>,
 Raj Kumar Rampelli <raj.kumar.rampelli@....com>, Vinod Koul
 <vkoul@...nel.org>, Michal Simek <michal.simek@....com>, Jan Kuliga
 <jankul@...tek.krakow.pl>, <dmaengine@...r.kernel.org>,
 <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
 <stable@...r.kernel.org>
Subject: Re: [PATCH 2/3] dmaengine: xilinx: xdma: Fix synchronization issue

Hi Lizhi,

> > @@ -376,6 +378,8 @@ static int xdma_xfer_start(struct xdma_chan *xchan)
> >   		return ret;  
> >   >   	xchan->busy = true;  
> > +	xchan->stop_requested = false;
> > +	reinit_completion(&xchan->last_interrupt);  
> 
> If stop_requested is true, it should not start another transfer. So I would suggest to add
> 
>       if (xchan->stop_requested)
> 
>                  return -ENODEV;

Maybe -EBUSY in this case?

I thought synchronize() was mandatory in-between. If that's not the
case then indeed we need to block or error-out if a new transfer
gets started.

> 
> at the beginning of xdma_xfer_start().
> 
> xdma_xfer_start() is protected by chan lock.
> 
> >   >   	return 0;  
> >   }

Thanks,
Miquèl