[RFC PATCH 2/2] dmaengine: altera: fix spinlock usage

[Sylvain Lesne <lesne@xxxxxxxxxxx>]

Since this lock is acquired in both process and IRQ context, failing to
to disable IRQs when trying to acquire the lock in process context can
lead to deadlocks.

Signed-off-by: Sylvain Lesne <lesne@xxxxxxxxxxx>
---
I'm not sure that this is the "smartest" fix, but I think something 
should be done to fix the spinlock usage in this driver (lockdep 
agrees!).
---
 drivers/dma/altera-msgdma.c | 35 +++++++++++++++++++++--------------
 1 file changed, 21 insertions(+), 14 deletions(-)

diff --git a/drivers/dma/altera-msgdma.c b/drivers/dma/altera-msgdma.c
index 35cbf2365f68..339186f25a2a 100644
--- a/drivers/dma/altera-msgdma.c
+++ b/drivers/dma/altera-msgdma.c
@@ -212,11 +212,12 @@ struct msgdma_device {
 static struct msgdma_sw_desc *msgdma_get_descriptor(struct msgdma_device *mdev)
 {
 	struct msgdma_sw_desc *desc;
+	unsigned long flags;
 
-	spin_lock_bh(&mdev->lock);
+	spin_lock_irqsave(&mdev->lock, flags);
 	desc = list_first_entry(&mdev->free_list, struct msgdma_sw_desc, node);
 	list_del(&desc->node);
-	spin_unlock_bh(&mdev->lock);
+	spin_unlock_irqrestore(&mdev->lock, flags);
 
 	INIT_LIST_HEAD(&desc->tx_list);
 
@@ -306,13 +307,14 @@ static dma_cookie_t msgdma_tx_submit(struct dma_async_tx_descriptor *tx)
 	struct msgdma_device *mdev = to_mdev(tx->chan);
 	struct msgdma_sw_desc *new;
 	dma_cookie_t cookie;
+	unsigned long flags;
 
 	new = tx_to_desc(tx);
-	spin_lock_bh(&mdev->lock);
+	spin_lock_irqsave(&mdev->lock, flags);
 	cookie = dma_cookie_assign(tx);
 
 	list_add_tail(&new->node, &mdev->pending_list);
-	spin_unlock_bh(&mdev->lock);
+	spin_unlock_irqrestore(&mdev->lock, flags);
 
 	return cookie;
 }
@@ -336,17 +338,18 @@ msgdma_prep_memcpy(struct dma_chan *dchan, dma_addr_t dma_dst,
 	struct msgdma_extended_desc *desc;
 	size_t copy;
 	u32 desc_cnt;
+	unsigned long irqflags;
 
 	desc_cnt = DIV_ROUND_UP(len, MSGDMA_MAX_TRANS_LEN);
 
-	spin_lock_bh(&mdev->lock);
+	spin_lock_irqsave(&mdev->lock, irqflags);
 	if (desc_cnt > mdev->desc_free_cnt) {
 		spin_unlock_bh(&mdev->lock);
 		dev_dbg(mdev->dev, "mdev %p descs are not available\n", mdev);
 		return NULL;
 	}
 	mdev->desc_free_cnt -= desc_cnt;
-	spin_unlock_bh(&mdev->lock);
+	spin_unlock_irqrestore(&mdev->lock, irqflags);
 
 	do {
 		/* Allocate and populate the descriptor */
@@ -397,18 +400,19 @@ msgdma_prep_slave_sg(struct dma_chan *dchan, struct scatterlist *sgl,
 	u32 desc_cnt = 0, i;
 	struct scatterlist *sg;
 	u32 stride;
+	unsigned long irqflags;
 
 	for_each_sg(sgl, sg, sg_len, i)
 		desc_cnt += DIV_ROUND_UP(sg_dma_len(sg), MSGDMA_MAX_TRANS_LEN);
 
-	spin_lock_bh(&mdev->lock);
+	spin_lock_irqsave(&mdev->lock, irqflags);
 	if (desc_cnt > mdev->desc_free_cnt) {
 		spin_unlock_bh(&mdev->lock);
 		dev_dbg(mdev->dev, "mdev %p descs are not available\n", mdev);
 		return NULL;
 	}
 	mdev->desc_free_cnt -= desc_cnt;
-	spin_unlock_bh(&mdev->lock);
+	spin_unlock_irqrestore(&mdev->lock, irqflags);
 
 	avail = sg_dma_len(sgl);
 
@@ -566,10 +570,11 @@ static void msgdma_start_transfer(struct msgdma_device *mdev)
 static void msgdma_issue_pending(struct dma_chan *chan)
 {
 	struct msgdma_device *mdev = to_mdev(chan);
+	unsigned long flags;
 
-	spin_lock_bh(&mdev->lock);
+	spin_lock_irqsave(&mdev->lock, flags);
 	msgdma_start_transfer(mdev);
-	spin_unlock_bh(&mdev->lock);
+	spin_unlock_irqrestore(&mdev->lock, flags);
 }
 
 /**
@@ -634,10 +639,11 @@ static void msgdma_free_descriptors(struct msgdma_device *mdev)
 static void msgdma_free_chan_resources(struct dma_chan *dchan)
 {
 	struct msgdma_device *mdev = to_mdev(dchan);
+	unsigned long flags;
 
-	spin_lock_bh(&mdev->lock);
+	spin_lock_irqsave(&mdev->lock, flags);
 	msgdma_free_descriptors(mdev);
-	spin_unlock_bh(&mdev->lock);
+	spin_unlock_irqrestore(&mdev->lock, flags);
 	kfree(mdev->sw_desq);
 }
 
@@ -682,8 +688,9 @@ static void msgdma_tasklet(unsigned long data)
 	u32 count;
 	u32 __maybe_unused size;
 	u32 __maybe_unused status;
+	unsigned long flags;
 
-	spin_lock(&mdev->lock);
+	spin_lock_irqsave(&mdev->lock, flags);
 
 	/* Read number of responses that are available */
 	count = ioread32(mdev->csr + MSGDMA_CSR_RESP_FILL_LEVEL);
@@ -704,7 +711,7 @@ static void msgdma_tasklet(unsigned long data)
 		msgdma_chan_desc_cleanup(mdev);
 	}
 
-	spin_unlock(&mdev->lock);
+	spin_unlock_irqrestore(&mdev->lock, flags);
 }
 
 /**
-- 
2.7.4

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