[PATCH] dmaengine: pl330: use lock of dma channel in pl330_update

[Hsin-Yu Chao]

The content of pl330_thread could be modified in pl330_update
without protection by the lock from the dma channel who currently
holding this thread. This could cause bug to the calculation of
in pl330_tx_status, if the running request has just been done and
moving to next request while calculating the residual number, an
invalid number from BUSY descriptor could be added up.
---
 drivers/dma/pl330.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
index 31e9c49..2449cb7 100644
--- a/drivers/dma/pl330.c
+++ b/drivers/dma/pl330.c
@@ -1564,6 +1564,19 @@ static void pl330_dotask(unsigned long data)
        return;
 }
 
+static struct dma_pl330_chan *get_dma_channel(struct pl330_dmac *pl330,
+                                             struct pl330_thread *thrd)
+{
+       struct dma_pl330_chan *pch;
+       int i;
+       for (i = 0; i < pl330->num_peripherals; i++) {
+               pch = &pl330->peripherals[i];
+               if (pch && pch->thread == thrd)
+                       return pch;
+       }
+       return NULL;
+}
+
 /* Returns 1 if state was updated, 0 otherwise */
 static int pl330_update(struct pl330_dmac *pl330)
 {
@@ -1613,6 +1626,7 @@ static int pl330_update(struct pl330_dmac *pl330)
        for (ev = 0; ev < pl330->pcfg.num_events; ev++) {
                if (val & (1 << ev)) { /* Event occurred */
                        struct pl330_thread *thrd;
+                       struct dma_pl330_chan *pch;
                        u32 inten = readl(regs + INTEN);
                        int active;
 
@@ -1625,6 +1639,9 @@ static int pl330_update(struct pl330_dmac *pl330)
                        id = pl330->events[ev];
 
                        thrd = &pl330->channels[id];
+                       pch = get_dma_channel(pl330, thrd);
+                       if (pch)
+                               spin_lock_irqsave(&pch->lock, flags);
 
                        active = thrd->req_running;
                        if (active == -1) /* Aborted */
@@ -1638,6 +1655,8 @@ static int pl330_update(struct pl330_dmac *pl330)
 
                        /* Get going again ASAP */
                        _start(thrd);
+                       if (pch)
+                               spin_unlock_irqrestore(&pch->lock, flags);
 
                        /* For now, just make a list of callbacks to be done */
                        list_add_tail(&descdone->rqd, &pl330->req_done);
-- 
2.6.6