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dmaengine: stm32-dma: fix potential race between pause and resume 

When disabling dma channel, a TCF flag is set and as TCIE is enabled, an
interrupt is raised.
On a busy system, the interrupt may have latency and the user can ask for
dmaengine_resume while stm32-dma driver has not yet managed the complete
pause (backup of registers to restore state in resume).
To avoid such a case, instead of waiting the interrupt to backup the
registers, do it just after disabling the channel and discard Transfer
Complete interrupt in case the channel is paused.

Fixes: 099a9a94be ("dmaengine: stm32-dma: add device_pause/device_resume support")
Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Link: https://lore.kernel.org/r/20221024083611.132588-1-amelie.delaunay@foss.st.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
This commit is contained in:
Amelie Delaunay 2022-10-24 10:36:11 +02:00 committed by Vinod Koul
parent ac2b9f34f0
commit 140fd5e74a
1 changed files with 6 additions and 8 deletions
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14
drivers/dma/stm32-dma.c
View File

@ -675,6 +675,8 @@ static void stm32_dma_handle_chan_paused(struct stm32_dma_chan *chan)
chan->chan_reg.dma_sndtr = stm32_dma_read(dmadev, STM32_DMA_SNDTR(chan->id));
chan->status = DMA_PAUSED;
dev_dbg(chan2dev(chan), "vchan %pK: paused\n", &chan->vchan);
}
@ -789,9 +791,7 @@ static irqreturn_t stm32_dma_chan_irq(int irq, void *devid)
if (status & STM32_DMA_TCI) {
stm32_dma_irq_clear(chan, STM32_DMA_TCI);
if (scr & STM32_DMA_SCR_TCIE) {
if (chan->status == DMA_PAUSED && !(scr & STM32_DMA_SCR_EN))
stm32_dma_handle_chan_paused(chan);
else
if (chan->status != DMA_PAUSED)
stm32_dma_handle_chan_done(chan, scr);
}
status &= ~STM32_DMA_TCI;
@ -838,13 +838,11 @@ static int stm32_dma_pause(struct dma_chan *c)
return -EPERM;
spin_lock_irqsave(&chan->vchan.lock, flags);
ret = stm32_dma_disable_chan(chan);
/*
* A transfer complete flag is set to indicate the end of transfer due to the stream
* interruption, so wait for interrupt
*/
if (!ret)
chan->status = DMA_PAUSED;
stm32_dma_handle_chan_paused(chan);
spin_unlock_irqrestore(&chan->vchan.lock, flags);
return ret;