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

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Date: Tue, 27 Feb 2024 20:21:23 -0800
From: Vishal Sagar <vishal.sagar@....com>
To: <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: [PATCH v2 1/2] dmaengine: xilinx: dpdma: Fix race condition in vsync IRQ

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(-)

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);
 }
 
-- 
2.25.1