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>

diff --git a/drivers/dma/at_xdmac.c b/drivers/dma/at_xdmac.c
index 933e4b338459284465d7970e3ff7dbf0f37314b8..0dcc9a7a90af66310984ca9832cd22c56bb49d6d 100644 (file)
--- 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;
 }