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SubjectRe: [PATCH] dmaengine: pl330: Fix unbalanced runtime PM
From
Hi Vinod,

在 2022/4/11 21:48, Vinod Koul 写道:
> On 26-03-22, 20:16, Sugar Zhang wrote:
>> 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(force)
> maybe unconditional is a better word than force here?
okay, will do in v2.
>
>> | |
>>
>> 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:
>> commit 5c9e6c2b2ba3 ("dmaengine: pl330: Fix runtime PM support for terminated transfers")
>> commit ae43b3289186 ("ARM: 8202/1: dmaengine: pl330: Add runtime Power Management support v12")
> That is not the right way for Fixes tag

like this?

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 <huibin.hong@rock-chips.com>
>> Signed-off-by: Sugar Zhang <sugar.zhang@rock-chips.com>
>> ---
>>
>> 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

--
Best Regards!
张学广/Sugar
瑞芯微电子股份有限公司
Rockchip Electronics Co., Ltd.

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