imx-sdma: fix pagefault when channel is disabled during interrupt

Add a spinlock and an 'enabled' boolean on channel descriptor, to avoid using buffer descriptors in the interrupt context,
when sdma_disable_channel is called meanwhile.

Signed-off-by Thierry Bultel <[email protected]>

---

Changes since V2:
* Applied Vinod Koul's review about empty lines

Changes since V1:
* Applied Shunyong Yang's review advice:
* Use a bool type for the enabled field
* Fixed the race condition

 drivers/dma/imx-sdma.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

drivers/dma/imx-sdma.c +1 -0

index d1651a5..0df6d54 100644
@@ -330,6 +330,7 @@ struct sdma_channel {
 	unsigned int			chn_real_count;
 	struct tasklet_struct		tasklet;
 	struct imx_dma_data		data;
+	bool				enabled;
 };
 
 #define IMX_DMA_SG_LOOP		BIT(0)

drivers/dma/imx-sdma.c +17 -0

 	writel(BIT(channel), sdma->regs + SDMA_H_START);
+
+	spin_lock_irqsave(&sdmac->lock, flags);
+	sdmac->enabled = 1;
+	spin_unlock_irqrestore(&sdmac->lock, flags);
 }
 
 /*

@@ -677,6 +684,14 @@ static void sdma_update_channel_loop(struct sdma_channel *sdmac)
 	struct sdma_buffer_descriptor *bd;
 	int error = 0;
 	enum dma_status	old_status = sdmac->status;
+	unsigned long flags;
+
+	spin_lock_irqsave(&sdmac->lock, flags);
+	if (!sdmac->enabled) {
+		spin_unlock_irqrestore(&sdmac->lock, flags);
+		return;
+	}
+	spin_unlock_irqrestore(&sdmac->lock, flags);
 
 	/*
 	 * loop mode. Iterate over descriptors, re-setup them and

@@ -930,10 +945,15 @@ static int sdma_disable_channel(struct dma_chan *chan)
 	struct sdma_channel *sdmac = to_sdma_chan(chan);
 	struct sdma_engine *sdma = sdmac->sdma;
 	int channel = sdmac->channel;
+	unsigned long flags;
 
 	writel_relaxed(BIT(channel), sdma->regs + SDMA_H_STATSTOP);
 	sdmac->status = DMA_ERROR;
 
+	spin_lock_irqsave(&sdmac->lock, flags);
+	sdmac->enabled = 0;
+	spin_unlock_irqrestore(&sdmac->lock, flags);
+
 	return 0;
 }
 

Signature · 6 lines

2.7.4

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