linux-kernel - RE: [PATCH v2 1/2] dmaengine: xilinx: dpdma: Fix race condition in vsync IRQ

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Date: Tue, 12 Mar 2024 15:56:34 +0000
From: "Sagar, Vishal" <vishal.sagar@....com>
To: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
	"laurent.pinchart@...asonboard.com" <laurent.pinchart@...asonboard.com>,
	"vkoul@...nel.org" <vkoul@...nel.org>
CC: "Simek, Michal" <michal.simek@....com>, "dmaengine@...r.kernel.org"
	<dmaengine@...r.kernel.org>, "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "Allagadapa, Varunkumar"
	<varunkumar.allagadapa@....com>
Subject: RE: [PATCH v2 1/2] dmaengine: xilinx: dpdma: Fix race condition in
 vsync IRQ

[AMD Official Use Only - General]

Hi Tomi,

> -----Original Message-----
> From: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
> Sent: Tuesday, March 12, 2024 1:34 AM
> To: Sagar, Vishal <vishal.sagar@....com>;
> laurent.pinchart@...asonboard.com; vkoul@...nel.org
> Cc: Simek, Michal <michal.simek@....com>; dmaengine@...r.kernel.org;
> linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org;
> Allagadapa, Varunkumar <varunkumar.allagadapa@....com>
> Subject: Re: [PATCH v2 1/2] dmaengine: xilinx: dpdma: Fix race condition in
> vsync IRQ
>
> Hi,
>
> On 28/02/2024 06:21, Vishal Sagar wrote:
> > From: Neel Gandhi <neel.gandhi@...inx.com>
> >
> > The vchan_next_desc() function, called from
> > xilinx_dpdma_chan_queue_transfer(), must be called with
> > virt_dma_chan.lock held. This isn't correctly handled in all code paths,
> > resulting in a race condition between the .device_issue_pending()
> > handler and the IRQ handler which causes DMA to randomly stop. Fix it by
> > taking the lock around xilinx_dpdma_chan_queue_transfer() calls that are
> > missing it.
> >
> > Signed-off-by: Neel Gandhi <neel.gandhi@....com>
> > Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@....com>
> > Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
> > Signed-off-by: Vishal Sagar <vishal.sagar@....com>
> >
> > Link: https://lore.kernel.org/all/20220122121407.11467-1-
> neel.gandhi@...inx.com
> > ---
> >   drivers/dma/xilinx/xilinx_dpdma.c | 10 ++++++++--
> >   1 file changed, 8 insertions(+), 2 deletions(-)
>
> This fixes a lockdep warning:
>
> WARNING: CPU: 1 PID: 466 at drivers/dma/xilinx/xilinx_dpdma.c:834
>
> Afaics, this issue has been around since the initial commit, in v5.10,
> and the fix applies on top of v5.10. I have tested this on v6.2, which
> is where the DP support was added to the board I have.
>
> So I think you can add:
>
> Fixes: 7cbb0c63de3f ("dmaengine: xilinx: dpdma: Add the Xilinx
> DisplayPort DMA engine driver")
>
>   Tomi
>

<snip>

Thanks for going through the patch.
I will add this to the commit message and resend v3.
I am still waiting for more reviews to happen.

Regards
Vishal Sagar