dmaengine: pl330: Return DMA_PAUSED when transaction is paused

pl330_pause() does not set anything to indicate paused condition which
causes pl330_tx_status() to return DMA_IN_PROGRESS. This breaks 8250
DMA flush after the fix in commit 57e9af7831dc ("serial: 8250_dma: Fix
DMA Rx rearm race"). The function comment for pl330_pause() claims
pause is supported but resume is not which is enough for 8250 DMA flush
to work as long as DMA status reports DMA_PAUSED when appropriate.

Add PAUSED state for descriptor and mark BUSY descriptors with PAUSED
in pl330_pause(). Return DMA_PAUSED from pl330_tx_status() when the
descriptor is PAUSED.

Reported-by: Richard Tresidder <rtresidd@electromag.com.au>
Tested-by: Richard Tresidder <rtresidd@electromag.com.au>
Fixes: 88987d2c7534 ("dmaengine: pl330: add DMA_PAUSE feature")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/linux-serial/f8a86ecd-64b1-573f-c2fa-59f541083f1a@electromag.com.au/
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20230526105434.14959-1-ilpo.jarvinen@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
index b4731fe6bbc14fc7360723726b535a6194383429..3cf0b38387ae5604adf7fbf07574444171c21043 100644 (file)
--- a/drivers/dma/pl330.c
+++ b/drivers/dma/pl330.c
@@ -403,6 +403,12 @@ enum desc_status {
         * of a channel can be BUSY at any time.
         */
        BUSY,
+       /*
+        * Pause was called while descriptor was BUSY. Due to hardware
+        * limitations, only termination is possible for descriptors
+        * that have been paused.
+        */
+       PAUSED,
        /*
         * Sitting on the channel work_list but xfer done
         * by PL330 core
@@ -2041,7 +2047,7 @@ static inline void fill_queue(struct dma_pl330_chan *pch)
        list_for_each_entry(desc, &pch->work_list, node) {
 
                /* If already submitted */
-               if (desc->status == BUSY)
+               if (desc->status == BUSY || desc->status == PAUSED)
                        continue;
 
                ret = pl330_submit_req(pch->thread, desc);
@@ -2326,6 +2332,7 @@ static int pl330_pause(struct dma_chan *chan)
 {
        struct dma_pl330_chan *pch = to_pchan(chan);
        struct pl330_dmac *pl330 = pch->dmac;
+       struct dma_pl330_desc *desc;
        unsigned long flags;
 
        pm_runtime_get_sync(pl330->ddma.dev);
@@ -2335,6 +2342,10 @@ static int pl330_pause(struct dma_chan *chan)
        _stop(pch->thread);
        spin_unlock(&pl330->lock);
 
+       list_for_each_entry(desc, &pch->work_list, node) {
+               if (desc->status == BUSY)
+                       desc->status = PAUSED;
+       }
        spin_unlock_irqrestore(&pch->lock, flags);
        pm_runtime_mark_last_busy(pl330->ddma.dev);
        pm_runtime_put_autosuspend(pl330->ddma.dev);
@@ -2425,7 +2436,7 @@ pl330_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
                else if (running && desc == running)
                        transferred =
                                pl330_get_current_xferred_count(pch, desc);
-               else if (desc->status == BUSY)
+               else if (desc->status == BUSY || desc->status == PAUSED)
                        /*
                         * Busy but not running means either just enqueued,
                         * or finished and not yet marked done
@@ -2442,6 +2453,9 @@ pl330_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
                        case DONE:
                                ret = DMA_COMPLETE;
                                break;
+                       case PAUSED:
+                               ret = DMA_PAUSED;
+                               break;
                        case PREP:
                        case BUSY:
                                ret = DMA_IN_PROGRESS;