linux-kernel - Re: [PATCH] spi: spi-zynqmp-gqspi: Fix runtime PM imbalance in zynqmp_qspi

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Date:   Fri, 9 Apr 2021 09:33:30 +0800
From:   "quanyang.wang" <quanyang.wang@...driver.com>
To:     Michal Simek <michal.simek@...inx.com>,
        Dinghao Liu <dinghao.liu@....edu.cn>, kjlu@....edu,
        Amit Kumar Mahapatra <amit.kumar-mahapatra@...inx.com>
Cc:     Mark Brown <broonie@...nel.org>, linux-spi@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] spi: spi-zynqmp-gqspi: Fix runtime PM imbalance in
 zynqmp_qspi_probe

Hi Dinghao,

On 4/8/21 6:33 PM, Michal Simek wrote:
> ++
>
> On 4/8/21 11:25 AM, Dinghao Liu wrote:
>> When platform_get_irq() fails, a pairing PM usage counter
>> increment is needed to keep the counter balanced. It's the
>> same for the following error paths.
>>
>> Signed-off-by: Dinghao Liu <dinghao.liu@....edu.cn>
>> ---
>>   drivers/spi/spi-zynqmp-gqspi.c | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/drivers/spi/spi-zynqmp-gqspi.c b/drivers/spi/spi-zynqmp-gqspi.c
>> index c8fa6ee18ae7..95963a2de64a 100644
>> --- a/drivers/spi/spi-zynqmp-gqspi.c
>> +++ b/drivers/spi/spi-zynqmp-gqspi.c
>> @@ -1197,6 +1197,7 @@ static int zynqmp_qspi_probe(struct platform_device *pdev)
>>   	return 0;
>>   
>>   clk_dis_all:
>> +	pm_runtime_get_noresume(&pdev->dev);
>>   	pm_runtime_set_suspended(&pdev->dev);
>>   	pm_runtime_disable(&pdev->dev);
>>   	clk_disable_unprepare(xqspi->refclk);
>>
The imbalance is because pm_runtime_put_autosuspend is called to make 
counter to be -1.

It looks strange that there is no counter increament op before 
pm_runtime_put_autosuspend.

In my limited understanding, it should look like:

......

pm_runtime_enable

pm_runtime_get_sync   //increase counter to one to resume device

DO OPERATIONS HERE

pm_runtime_mark_last_busy
pm_runtime_put_autosuspend   //decrease counter to zero and trigger suspend

return 0;

error_path:

pm_runtime_put_sync

pm_runtime_disable

return err;


Am I missing something?

Thanks,

Quanyang