ARM: PL08x: fix locking between prepare function and submit function

The PL08x driver holds on to the channel lock with interrupts disabled
between the prepare and the subsequent submit API functions.  This
means that the locking state when the prepare function returns is
dependent on whether it suceeeds or not.

It did this to ensure that the physical channel wasn't released, and
as it used to add the descriptor onto the pending list at prepare time
rather than submit time.

Now that we have reorganized the code to remove those reasons, we can
now safely release the spinlock at the end of preparation and reacquire
it in our submit function.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 9 insertions, 19 deletions

diff --git a/drivers/dma/amba-pl08x.c b/drivers/dma/amba-pl08x.c
index bf6f7d02c9f6..1c9f712520d6 100644
--- a/drivers/dma/amba-pl08x.c
+++ b/drivers/dma/amba-pl08x.c
@@ -981,6 +981,9 @@ static dma_cookie_t pl08x_tx_submit(struct dma_async_tx_descriptor *tx)
 {
         struct pl08x_dma_chan *plchan = to_pl08x_chan(tx->chan);
         struct pl08x_txd *txd = to_pl08x_txd(tx);
+        unsigned long flags;
+
+        spin_lock_irqsave(&plchan->lock, flags);
 
         plchan->chan.cookie += 1;
         if (plchan->chan.cookie < 0)
@@ -1003,8 +1006,7 @@ static dma_cookie_t pl08x_tx_submit(struct dma_async_tx_descriptor *tx)
                 plchan->phychan_hold--;
         }
 
-        /* This unlock follows the lock in the prep() function */
-        spin_unlock_irqrestore(&plchan->lock, plchan->lockflags);
+        spin_unlock_irqrestore(&plchan->lock, flags);
 
         return tx->cookie;
 }
@@ -1225,9 +1227,9 @@ static void pl08x_issue_pending(struct dma_chan *chan)
 static int pl08x_prep_channel_resources(struct pl08x_dma_chan *plchan,
                                         struct pl08x_txd *txd)
 {
-        int num_llis;
         struct pl08x_driver_data *pl08x = plchan->host;
-        int ret;
+        unsigned long flags;
+        int num_llis, ret;
 
         num_llis = pl08x_fill_llis_for_desc(pl08x, txd);
         if (!num_llis) {
@@ -1235,7 +1237,7 @@ static int pl08x_prep_channel_resources(struct pl08x_dma_chan *plchan,
                 return -EINVAL;
         }
 
-        spin_lock_irqsave(&plchan->lock, plchan->lockflags);
+        spin_lock_irqsave(&plchan->lock, flags);
 
         /*
          * See if we already have a physical channel allocated,
@@ -1258,7 +1260,7 @@ static int pl08x_prep_channel_resources(struct pl08x_dma_chan *plchan,
                 if (plchan->slave) {
                         pl08x_free_txd_list(pl08x, plchan);
                         pl08x_free_txd(pl08x, txd);
-                        spin_unlock_irqrestore(&plchan->lock, plchan->lockflags);
+                        spin_unlock_irqrestore(&plchan->lock, flags);
                         return -EBUSY;
                 }
         } else
@@ -1272,11 +1274,7 @@ static int pl08x_prep_channel_resources(struct pl08x_dma_chan *plchan,
                 if (plchan->state == PL08X_CHAN_IDLE)
                         plchan->state = PL08X_CHAN_PAUSED;
 
-        /*
-         * Notice that we leave plchan->lock locked on purpose:
-         * it will be unlocked in the subsequent tx_submit()
-         * call. This is a consequence of the current API.
-         */
+        spin_unlock_irqrestore(&plchan->lock, flags);
 
         return 0;
 }
@@ -1355,10 +1353,6 @@ static struct dma_async_tx_descriptor *pl08x_prep_dma_memcpy(
         ret = pl08x_prep_channel_resources(plchan, txd);
         if (ret)
                 return NULL;
-        /*
-         * NB: the channel lock is held at this point so tx_submit()
-         * must be called in direct succession.
-         */
 
         return &txd->tx;
 }
@@ -1444,10 +1438,6 @@ static struct dma_async_tx_descriptor *pl08x_prep_slave_sg(
         ret = pl08x_prep_channel_resources(plchan, txd);
         if (ret)
                 return NULL;
-        /*
-         * NB: the channel lock is held at this point so tx_submit()
-         * must be called in direct succession.
-         */
 
         return &txd->tx;
 }