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+ #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 <ludovic.desroches@atmel.com>
Cc: stable@vger.kernel.org # 4.0 and later
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

1 files changed, 43 insertions, 32 deletions

diff --git a/drivers/dma/at_xdmac.c b/drivers/dma/at_xdmac.c
index 933e4b338459..0dcc9a7a90af 100644
--- a/drivers/dma/at_xdmac.c
+++ b/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;
 
         dev_dbg(chan2dev(chan), "%s: buf_addr=%pad, buf_len=%zd, period_len=%zd, dir=%s, flags=0x%lx\n",
                 __func__, &buf_addr, buf_len, period_len,
@@ -682,16 +686,16 @@ 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);
@@ -766,6 +770,7 @@ 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);
@@ -798,9 +803,9 @@ 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)
@@ -886,6 +891,7 @@ 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)
@@ -894,7 +900,7 @@ 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);
 
@@ -904,8 +910,7 @@ 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;
@@ -936,14 +941,14 @@ 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;
 }
 
@@ -964,8 +969,9 @@ 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
@@ -980,7 +986,7 @@ 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)
@@ -1116,12 +1122,13 @@ 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;
 }
@@ -1130,18 +1137,19 @@ 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;
 }
@@ -1150,18 +1158,19 @@ 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);
+        spin_lock_irqsave(&atchan->lock, flags);
         if (!at_xdmac_chan_is_paused(atchan)) {
-                spin_unlock_bh(&atchan->lock);
+                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;
 }
@@ -1171,10 +1180,11 @@ 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();
@@ -1184,7 +1194,7 @@ 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;
 }
@@ -1194,8 +1204,9 @@ 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),
@@ -1226,7 +1237,7 @@ 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;
 }