dmaengine: at_xdmac: lock fixes

Using _bh variant for spin locks causes this kind of warning:
Starting logging: ------------[ cut here ]------------
WARNING: CPU: 0 PID: 3 at /ssd_drive/linux/kernel/softirq.c:151
__local_bh_enable_ip+0xe8/0xf4()
Modules linked in:
CPU: 0 PID: 3 Comm: ksoftirqd/0 Not tainted 4.1.0-rc2+ torvalds#94
Hardware name: Atmel SAMA5
[<c0013c04>] (unwind_backtrace) from [<c00118a4>] (show_stack+0x10/0x14)
[<c00118a4>] (show_stack) from [<c001bbcc>]
(warn_slowpath_common+0x80/0xac)
[<c001bbcc>] (warn_slowpath_common) from [<c001bc14>]
(warn_slowpath_null+0x1c/0x24)
[<c001bc14>] (warn_slowpath_null) from [<c001e28c>]
(__local_bh_enable_ip+0xe8/0xf4)
[<c001e28c>] (__local_bh_enable_ip) from [<c01fdbd0>]
(at_xdmac_device_terminate_all+0xf4/0x100)
[<c01fdbd0>] (at_xdmac_device_terminate_all) from [<c02221a4>]
(atmel_complete_tx_dma+0x34/0xf4)
[<c02221a4>] (atmel_complete_tx_dma) from [<c01fe4ac>]
(at_xdmac_tasklet+0x14c/0x1ac)
[<c01fe4ac>] (at_xdmac_tasklet) from [<c001de58>]
(tasklet_action+0x68/0xb4)
[<c001de58>] (tasklet_action) from [<c001dfdc>]
(__do_softirq+0xfc/0x238)
[<c001dfdc>] (__do_softirq) from [<c001e140>] (run_ksoftirqd+0x28/0x34)
[<c001e140>] (run_ksoftirqd) from [<c0033a3c>]
(smpboot_thread_fn+0x138/0x18c)
[<c0033a3c>] (smpboot_thread_fn) from [<c0030e7c>] (kthread+0xdc/0xf0)
[<c0030e7c>] (kthread) from [<c000f480>] (ret_from_fork+0x14/0x34)
---[ end trace b57b14a99c1d8812 ]---

It comes from the fact that devices can called some code from the DMA
controller with irq disabled. _bh variant is not intended to be used in
this case since it can enable irqs. Switch to irqsave/irqrestore variant to
avoid this situation.

Signed-off-by: Ludovic Desroches <[email protected]>
Cc: [email protected] # 4.0 and later

Author: ldesroches

Diff for: drivers/dma/at_xdmac.c

@@ -415,8 +415,9 @@ static dma_cookie_t at_xdmac_tx_submit(struct dma_async_tx_descriptor *tx)
 	struct at_xdmac_desc	*desc = txd_to_at_desc(tx);
 	struct at_xdmac_chan	*atchan = to_at_xdmac_chan(tx->chan);
 	dma_cookie_t		cookie;
+	unsigned long		irqflags;
 
-	spin_lock_bh(&atchan->lock);
+	spin_lock_irqsave(&atchan->lock, irqflags);
 	cookie = dma_cookie_assign(tx);
 
 	dev_vdbg(chan2dev(tx->chan), "%s: atchan 0x%p, add desc 0x%p to xfers_list\n",
@@ -425,7 +426,7 @@ static dma_cookie_t at_xdmac_tx_submit(struct dma_async_tx_descriptor *tx)
 	if (list_is_singular(&atchan->xfers_list))
 		at_xdmac_start_xfer(atchan, desc);
 
-	spin_unlock_bh(&atchan->lock);
+	spin_unlock_irqrestore(&atchan->lock, irqflags);
 	return cookie;
 }
 
@@ -563,6 +564,8 @@ at_xdmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
 	struct scatterlist	*sg;
 	int			i;
 	unsigned int		xfer_size = 0;
+	unsigned long		irqflags;
+	struct dma_async_tx_descriptor	*ret = NULL;
 
 	if (!sgl)
 		return NULL;
@@ -578,7 +581,7 @@ at_xdmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
 		 flags);
 
 	/* Protect dma_sconfig field that can be modified by set_slave_conf. */
-	spin_lock_bh(&atchan->lock);
+	spin_lock_irqsave(&atchan->lock, irqflags);
 
 	/* Prepare descriptors. */
 	for_each_sg(sgl, sg, sg_len, i) {
@@ -589,8 +592,7 @@ at_xdmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
 		mem = sg_dma_address(sg);
 		if (unlikely(!len)) {
 			dev_err(chan2dev(chan), "sg data length is zero\n");
-			spin_unlock_bh(&atchan->lock);
-			return NULL;
+			goto spin_unlock;
 		}
 		dev_dbg(chan2dev(chan), "%s: * sg%d len=%u, mem=0x%08x\n",
 			 __func__, i, len, mem);
@@ -600,8 +602,7 @@ at_xdmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
 			dev_err(chan2dev(chan), "can't get descriptor\n");
 			if (first)
 				list_splice_init(&first->descs_list, &atchan->free_descs_list);
-			spin_unlock_bh(&atchan->lock);
-			return NULL;
+			goto spin_unlock;
 		}
 
 		/* Linked list descriptor setup. */
@@ -645,13 +646,15 @@ at_xdmac_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
 		xfer_size += len;
 	}
 
-	spin_unlock_bh(&atchan->lock);
 
 	first->tx_dma_desc.flags = flags;
 	first->xfer_size = xfer_size;
 	first->direction = direction;
+	ret = &first->tx_dma_desc;
 
-	return &first->tx_dma_desc;
+spin_unlock:
+	spin_unlock_irqrestore(&atchan->lock, irqflags);
+	return ret;
 }
 
 static struct dma_async_tx_descriptor *
@@ -664,6 +667,7 @@ at_xdmac_prep_dma_cyclic(struct dma_chan *chan, dma_addr_t buf_addr,
 	struct at_xdmac_desc	*first = NULL, *prev = NULL;
 	unsigned int		periods = buf_len / period_len;
 	int			i;
+	unsigned long		irqflags;
 	u32			cfg;
 
 	dev_dbg(chan2dev(chan), "%s: buf_addr=%pad, buf_len=%zd, period_len=%zd, dir=%s, flags=0x%lx\n",
@@ -683,16 +687,16 @@ at_xdmac_prep_dma_cyclic(struct dma_chan *chan, dma_addr_t buf_addr,
 	for (i = 0; i < periods; i++) {
 		struct at_xdmac_desc	*desc = NULL;
 
-		spin_lock_bh(&atchan->lock);
+		spin_lock_irqsave(&atchan->lock, irqflags);
 		desc = at_xdmac_get_desc(atchan);
 		if (!desc) {
 			dev_err(chan2dev(chan), "can't get descriptor\n");
 			if (first)
 				list_splice_init(&first->descs_list, &atchan->free_descs_list);
-			spin_unlock_bh(&atchan->lock);
+			spin_unlock_irqrestore(&atchan->lock, irqflags);
 			return NULL;
 		}
-		spin_unlock_bh(&atchan->lock);
+		spin_unlock_irqrestore(&atchan->lock, irqflags);
 		dev_dbg(chan2dev(chan),
 			"%s: desc=0x%p, tx_dma_desc.phys=%pad\n",
 			__func__, desc, &desc->tx_dma_desc.phys);
@@ -767,6 +771,7 @@ at_xdmac_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
 					| AT_XDMAC_CC_SIF(0)
 					| AT_XDMAC_CC_MBSIZE_SIXTEEN
 					| AT_XDMAC_CC_TYPE_MEM_TRAN;
+	unsigned long		irqflags;
 
 	dev_dbg(chan2dev(chan), "%s: src=%pad, dest=%pad, len=%zd, flags=0x%lx\n",
 		__func__, &src, &dest, len, flags);
@@ -799,9 +804,9 @@ at_xdmac_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
 
 		dev_dbg(chan2dev(chan), "%s: remaining_size=%zu\n", __func__, remaining_size);
 
-		spin_lock_bh(&atchan->lock);
+		spin_lock_irqsave(&atchan->lock, irqflags);
 		desc = at_xdmac_get_desc(atchan);
-		spin_unlock_bh(&atchan->lock);
+		spin_unlock_irqrestore(&atchan->lock, irqflags);
 		if (!desc) {
 			dev_err(chan2dev(chan), "can't get descriptor\n");
 			if (first)
@@ -887,6 +892,7 @@ at_xdmac_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
 	int			residue;
 	u32			cur_nda, mask, value;
 	u8			dwidth = 0;
+	unsigned long		flags;
 
 	ret = dma_cookie_status(chan, cookie, txstate);
 	if (ret == DMA_COMPLETE)
@@ -895,7 +901,7 @@ at_xdmac_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
 	if (!txstate)
 		return ret;
 
-	spin_lock_bh(&atchan->lock);
+	spin_lock_irqsave(&atchan->lock, flags);
 
 	desc = list_first_entry(&atchan->xfers_list, struct at_xdmac_desc, xfer_node);
 
@@ -905,8 +911,7 @@ at_xdmac_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
 	 */
 	if (!desc->active_xfer) {
 		dma_set_residue(txstate, desc->xfer_size);
-		spin_unlock_bh(&atchan->lock);
-		return ret;
+		goto spin_unlock;
 	}
 
 	residue = desc->xfer_size;
@@ -937,14 +942,14 @@ at_xdmac_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
 	}
 	residue += at_xdmac_chan_read(atchan, AT_XDMAC_CUBC) << dwidth;
 
-	spin_unlock_bh(&atchan->lock);
-
 	dma_set_residue(txstate, residue);
 
 	dev_dbg(chan2dev(chan),
 		 "%s: desc=0x%p, tx_dma_desc.phys=%pad, tx_status=%d, cookie=%d, residue=%d\n",
 		 __func__, desc, &desc->tx_dma_desc.phys, ret, cookie, residue);
 
+spin_unlock:
+	spin_unlock_irqrestore(&atchan->lock, flags);
 	return ret;
 }
 
@@ -965,8 +970,9 @@ static void at_xdmac_remove_xfer(struct at_xdmac_chan *atchan,
 static void at_xdmac_advance_work(struct at_xdmac_chan *atchan)
 {
 	struct at_xdmac_desc	*desc;
+	unsigned long		flags;
 
-	spin_lock_bh(&atchan->lock);
+	spin_lock_irqsave(&atchan->lock, flags);
 
 	/*
 	 * If channel is enabled, do nothing, advance_work will be triggered
@@ -981,7 +987,7 @@ static void at_xdmac_advance_work(struct at_xdmac_chan *atchan)
 			at_xdmac_start_xfer(atchan, desc);
 	}
 
-	spin_unlock_bh(&atchan->lock);
+	spin_unlock_irqrestore(&atchan->lock, flags);
 }
 
 static void at_xdmac_handle_cyclic(struct at_xdmac_chan *atchan)
@@ -1117,12 +1123,13 @@ static int at_xdmac_device_config(struct dma_chan *chan,
 {
 	struct at_xdmac_chan	*atchan = to_at_xdmac_chan(chan);
 	int ret;
+	unsigned long		flags;
 
 	dev_dbg(chan2dev(chan), "%s\n", __func__);
 
-	spin_lock_bh(&atchan->lock);
+	spin_lock_irqsave(&atchan->lock, flags);
 	ret = at_xdmac_set_slave_config(chan, config);
-	spin_unlock_bh(&atchan->lock);
+	spin_unlock_irqrestore(&atchan->lock, flags);
 
 	return ret;
 }
@@ -1131,18 +1138,19 @@ static int at_xdmac_device_pause(struct dma_chan *chan)
 {
 	struct at_xdmac_chan	*atchan = to_at_xdmac_chan(chan);
 	struct at_xdmac		*atxdmac = to_at_xdmac(atchan->chan.device);
+	unsigned long		flags;
 
 	dev_dbg(chan2dev(chan), "%s\n", __func__);
 
 	if (test_and_set_bit(AT_XDMAC_CHAN_IS_PAUSED, &atchan->status))
 		return 0;
 
-	spin_lock_bh(&atchan->lock);
+	spin_lock_irqsave(&atchan->lock, flags);
 	at_xdmac_write(atxdmac, AT_XDMAC_GRWS, atchan->mask);
 	while (at_xdmac_chan_read(atchan, AT_XDMAC_CC)
 	       & (AT_XDMAC_CC_WRIP | AT_XDMAC_CC_RDIP))
 		cpu_relax();
-	spin_unlock_bh(&atchan->lock);
+	spin_unlock_irqrestore(&atchan->lock, flags);
 
 	return 0;
 }
@@ -1151,16 +1159,19 @@ static int at_xdmac_device_resume(struct dma_chan *chan)
 {
 	struct at_xdmac_chan	*atchan = to_at_xdmac_chan(chan);
 	struct at_xdmac		*atxdmac = to_at_xdmac(atchan->chan.device);
+	unsigned long		flags;
 
 	dev_dbg(chan2dev(chan), "%s\n", __func__);
 
-	spin_lock_bh(&atchan->lock);
-	if (!at_xdmac_chan_is_paused(atchan))
+	spin_lock_irqsave(&atchan->lock, flags);
+	if (!at_xdmac_chan_is_paused(atchan)) {
+		spin_unlock_irqrestore(&atchan->lock, flags);
 		return 0;
+	}
 
 	at_xdmac_write(atxdmac, AT_XDMAC_GRWR, atchan->mask);
 	clear_bit(AT_XDMAC_CHAN_IS_PAUSED, &atchan->status);
-	spin_unlock_bh(&atchan->lock);
+	spin_unlock_irqrestore(&atchan->lock, flags);
 
 	return 0;
 }
@@ -1170,10 +1181,11 @@ static int at_xdmac_device_terminate_all(struct dma_chan *chan)
 	struct at_xdmac_desc	*desc, *_desc;
 	struct at_xdmac_chan	*atchan = to_at_xdmac_chan(chan);
 	struct at_xdmac		*atxdmac = to_at_xdmac(atchan->chan.device);
+	unsigned long		flags;
 
 	dev_dbg(chan2dev(chan), "%s\n", __func__);
 
-	spin_lock_bh(&atchan->lock);
+	spin_lock_irqsave(&atchan->lock, flags);
 	at_xdmac_write(atxdmac, AT_XDMAC_GD, atchan->mask);
 	while (at_xdmac_read(atxdmac, AT_XDMAC_GS) & atchan->mask)
 		cpu_relax();
@@ -1183,7 +1195,7 @@ static int at_xdmac_device_terminate_all(struct dma_chan *chan)
 		at_xdmac_remove_xfer(atchan, desc);
 
 	clear_bit(AT_XDMAC_CHAN_IS_CYCLIC, &atchan->status);
-	spin_unlock_bh(&atchan->lock);
+	spin_unlock_irqrestore(&atchan->lock, flags);
 
 	return 0;
 }
@@ -1193,8 +1205,9 @@ static int at_xdmac_alloc_chan_resources(struct dma_chan *chan)
 	struct at_xdmac_chan	*atchan = to_at_xdmac_chan(chan);
 	struct at_xdmac_desc	*desc;
 	int			i;
+	unsigned long		flags;
 
-	spin_lock_bh(&atchan->lock);
+	spin_lock_irqsave(&atchan->lock, flags);
 
 	if (at_xdmac_chan_is_enabled(atchan)) {
 		dev_err(chan2dev(chan),
@@ -1225,7 +1238,7 @@ static int at_xdmac_alloc_chan_resources(struct dma_chan *chan)
 	dev_dbg(chan2dev(chan), "%s: allocated %d descriptors\n", __func__, i);
 
 spin_unlock:
-	spin_unlock_bh(&atchan->lock);
+	spin_unlock_irqrestore(&atchan->lock, flags);
 	return i;
 }