Re: [PATCH 1/2] soundwire: qcom: fix unbalanced pm_runtime_put()

[Pierre-Louis Bossart]

On 5/17/23 11:37, Krzysztof Kozlowski wrote:
> This reverts commit 57ed510b0547 ("soundwire: qcom: use
> pm_runtime_resume_and_get()") which introduced unbalanced
> pm_runtime_put(), when device did not have runtime PM enabled.
> 
> If pm_runtime_resume_and_get() failed with -EACCES, the driver continued
> execution and finally called pm_runtime_put_autosuspend().  Since
> pm_runtime_resume_and_get() drops the usage counter on every error, this
> lead to double decrement of that counter visible in certain debugfs
> actions on unattached devices (still in reset state):
> 
>   $ cat /sys/kernel/debug/soundwire/master-0-0/sdw:0:0217:f001:00:0/registers
>   qcom-soundwire 3210000.soundwire-controller: swrm_wait_for_wr_fifo_avail err write overflow
>   soundwire sdw-master-0: trf on Slave 1 failed:-5 read addr e36 count 1
>   soundwire sdw:0:0217:f001:00:0: Runtime PM usage count underflow!
> 
> Fixes: 57ed510b0547 ("soundwire: qcom: use pm_runtime_resume_and_get()")
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>

Yes, this resume_and_get() added more problems indeed. One of those
well-intended changes that went sideways.

Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>


> ---
>  drivers/soundwire/qcom.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/soundwire/qcom.c b/drivers/soundwire/qcom.c
> index aad5942e5980..f442280af9d3 100644
> --- a/drivers/soundwire/qcom.c
> +++ b/drivers/soundwire/qcom.c
> @@ -614,11 +614,12 @@ static irqreturn_t qcom_swrm_wake_irq_handler(int irq, void *dev_id)
>  	struct qcom_swrm_ctrl *ctrl = dev_id;
>  	int ret;
>  
> -	ret = pm_runtime_resume_and_get(ctrl->dev);
> +	ret = pm_runtime_get_sync(ctrl->dev);
>  	if (ret < 0 && ret != -EACCES) {
>  		dev_err_ratelimited(ctrl->dev,
> -				    "pm_runtime_resume_and_get failed in %s, ret %d\n",
> +				    "pm_runtime_get_sync failed in %s, ret %d\n",
>  				    __func__, ret);
> +		pm_runtime_put_noidle(ctrl->dev);
>  		return ret;
>  	}
>  
> @@ -1197,11 +1198,12 @@ static int qcom_swrm_startup(struct snd_pcm_substream *substream,
>  	struct snd_soc_dai *codec_dai;
>  	int ret, i;
>  
> -	ret = pm_runtime_resume_and_get(ctrl->dev);
> +	ret = pm_runtime_get_sync(ctrl->dev);
>  	if (ret < 0 && ret != -EACCES) {
>  		dev_err_ratelimited(ctrl->dev,
> -				    "pm_runtime_resume_and_get failed in %s, ret %d\n",
> +				    "pm_runtime_get_sync failed in %s, ret %d\n",
>  				    __func__, ret);
> +		pm_runtime_put_noidle(ctrl->dev);
>  		return ret;
>  	}
>  
> @@ -1402,11 +1404,12 @@ static int swrm_reg_show(struct seq_file *s_file, void *data)
>  	struct qcom_swrm_ctrl *ctrl = s_file->private;
>  	int reg, reg_val, ret;
>  
> -	ret = pm_runtime_resume_and_get(ctrl->dev);
> +	ret = pm_runtime_get_sync(ctrl->dev);
>  	if (ret < 0 && ret != -EACCES) {
>  		dev_err_ratelimited(ctrl->dev,
> -				    "pm_runtime_resume_and_get failed in %s, ret %d\n",
> +				    "pm_runtime_get_sync failed in %s, ret %d\n",
>  				    __func__, ret);
> +		pm_runtime_put_noidle(ctrl->dev);
>  		return ret;
>  	}
>