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Message-ID: <b08c99fe-c221-4eb8-9b1a-1420cb5c32f3@ideasonboard.com>
Date: Tue, 12 Mar 2024 10:33:32 +0200
From: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To: Vishal Sagar <vishal.sagar@....com>, laurent.pinchart@...asonboard.com,
vkoul@...nel.org
Cc: michal.simek@....com, dmaengine@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
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@xilinx.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
> diff --git a/drivers/dma/xilinx/xilinx_dpdma.c b/drivers/dma/xilinx/xilinx_dpdma.c
> index b82815e64d24..28d9af8f00f0 100644
> --- a/drivers/dma/xilinx/xilinx_dpdma.c
> +++ b/drivers/dma/xilinx/xilinx_dpdma.c
> @@ -1097,12 +1097,14 @@ static void xilinx_dpdma_chan_vsync_irq(struct xilinx_dpdma_chan *chan)
> * Complete the active descriptor, if any, promote the pending
> * descriptor to active, and queue the next transfer, if any.
> */
> + spin_lock(&chan->vchan.lock);
> if (chan->desc.active)
> vchan_cookie_complete(&chan->desc.active->vdesc);
> chan->desc.active = pending;
> chan->desc.pending = NULL;
>
> xilinx_dpdma_chan_queue_transfer(chan);
> + spin_unlock(&chan->vchan.lock);
>
> out:
> spin_unlock_irqrestore(&chan->lock, flags);
> @@ -1264,10 +1266,12 @@ static void xilinx_dpdma_issue_pending(struct dma_chan *dchan)
> struct xilinx_dpdma_chan *chan = to_xilinx_chan(dchan);
> unsigned long flags;
>
> - spin_lock_irqsave(&chan->vchan.lock, flags);
> + spin_lock_irqsave(&chan->lock, flags);
> + spin_lock(&chan->vchan.lock);
> if (vchan_issue_pending(&chan->vchan))
> xilinx_dpdma_chan_queue_transfer(chan);
> - spin_unlock_irqrestore(&chan->vchan.lock, flags);
> + spin_unlock(&chan->vchan.lock);
> + spin_unlock_irqrestore(&chan->lock, flags);
> }
>
> static int xilinx_dpdma_config(struct dma_chan *dchan,
> @@ -1495,7 +1499,9 @@ static void xilinx_dpdma_chan_err_task(struct tasklet_struct *t)
> XILINX_DPDMA_EINTR_CHAN_ERR_MASK << chan->id);
>
> spin_lock_irqsave(&chan->lock, flags);
> + spin_lock(&chan->vchan.lock);
> xilinx_dpdma_chan_queue_transfer(chan);
> + spin_unlock(&chan->vchan.lock);
> spin_unlock_irqrestore(&chan->lock, flags);
> }
>
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