[v4] imx-sdma: fix pagefault when channel is disabled during interrupt

[v4] imx-sdma: fix pagefault when channel is disabled during interrupt

[Thierry Bultel]

Add a spinlock and a '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 <tbultel@pixelsurmer.com>
---

Changes since V3:
 * Uses true/false for enabled
 * Added missing empty line

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 | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
index d1651a5..497a881 100644
--- a/drivers/dma/imx-sdma.c
+++ b/drivers/dma/imx-sdma.c
@@ -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)
@@ -588,7 +589,14 @@ static int sdma_config_ownership(struct sdma_channel *sdmac,
 
 static void sdma_enable_channel(struct sdma_engine *sdma, int channel)
 {
+	unsigned long flags;
+	struct sdma_channel *sdmac = &sdma->channel[channel];
+
 	writel(BIT(channel), sdma->regs + SDMA_H_START);
+
+	spin_lock_irqsave(&sdmac->lock, flags);
+	sdmac->enabled = true;
+	spin_unlock_irqrestore(&sdmac->lock, flags);
 }
 
 /*
@@ -677,6 +685,14 @@ 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 +946,15 @@ 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 = false;
+	spin_unlock_irqrestore(&sdmac->lock, flags);
+
 	return 0;
 }
 

[v4] imx-sdma: fix pagefault when channel is disabled during interrupt

[Vinod Koul]

On Mon, Mar 05, 2018 at 02:27:18PM +0100, Thierry Bultel wrote:
> Add a spinlock and a 'enabled' boolean on channel descriptor, to avoid
> using buffer descriptors in the interrupt context,
> when sdma_disable_channel is called meanwhile.

Applied after adding subsytem tag, thanks