This driver use runtime PM autosuspend mechanism to manager clk.
pm_runtime_use_autosuspend(&adev->dev);
pm_runtime_set_autosuspend_delay(&adev->dev, PL330_AUTOSUSPEND_DELAY);
So, after ref count reached to zero, it will enter suspend
after the delay time elapsed.
The unbalanced PM:
* May cause dmac the next start failed.
* May cause dmac read unexpected state.
* May cause dmac stall if power down happen at the middle of the transfer.
e.g. may lose ack from AXI bus and stall.
Considering the following situation:
DMA TERMINATE TASKLET ROUTINE
| |
| issue_pending
| |
| pch->active = true
| pm_runtime_get
pm_runtime_put(if active) |
pch->active = false |
| work_list empty
| |
| pm_runtime_put(unconditional)
| |
At this point, it's unbalanced(1 get / 2 put).
After this patch:
DMA TERMINATE TASKLET ROUTINE
| |
| issue_pending
| |
| pch->active = true
| pm_runtime_get
pm_runtime_put(if active) |
pch->active = false |
| work_list empty
| |
| pm_runtime_put(if active)
| |
Now, it's balanced(1 get / 1 put).
Fixes: 5c9e6c2b2ba3 ("dmaengine: pl330: Fix runtime PM support for terminated transfers")
Fixes: ae43b3289186 ("ARM: 8202/1: dmaengine: pl330: Add runtime Power Management support v12")
Signed-off-by: Huibin Hong <[email protected]>
Signed-off-by: Sugar Zhang <[email protected]>
---
Changes in v2:
- fixup commit message per Vinod suggestion.
drivers/dma/pl330.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
index 858400e..ccd430e 100644
--- a/drivers/dma/pl330.c
+++ b/drivers/dma/pl330.c
@@ -2084,7 +2084,7 @@ static void pl330_tasklet(struct tasklet_struct *t)
spin_lock(&pch->thread->dmac->lock);
_stop(pch->thread);
spin_unlock(&pch->thread->dmac->lock);
- power_down = true;
+ power_down = pch->active;
pch->active = false;
} else {
/* Make sure the PL330 Channel thread is active */
--
2.7.4