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Subject[PATCH v2 1/2] dmaengine: xilinx: dpdma: Fix race condition in vsync IRQ
Date
From: Neel Gandhi <neel.gandhi@xilinx.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@amd.com>
Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey@amd.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Signed-off-by: Vishal Sagar <vishal.sagar@amd.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

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