linux-kernel - Re: [PATCH v9 4/4] sd: change to auto suspend mode

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Message-ID: <5111BBA1.4010200@intel.com>
Date:	Wed, 06 Feb 2013 10:10:41 +0800
From:	Aaron Lu <aaron.lu@...el.com>
To:	Alan Stern <stern@...land.harvard.edu>
CC:	Jens Axboe <axboe@...nel.dk>, "Rafael J. Wysocki" <rjw@...k.pl>,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	linux-pm@...r.kernel.org, linux-scsi@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org,
	Aaron Lu <aaron.lwe@...il.com>,
	Shane Huang <shane.huang@....com>
Subject: Re: [PATCH v9 4/4] sd: change to auto suspend mode

On 02/06/2013 12:51 AM, Alan Stern wrote:
> On Tue, 5 Feb 2013, Aaron Lu wrote:
> 
>> From: Lin Ming <ming.m.lin@...el.com>
>>
>> Uses block layer runtime pm helper functions in
>> scsi_runtime_suspend/resume for devices that take advantage of it.
>>
>> Remove scsi_autopm_* from sd open/release path and check_events path.
> 
> One thing is a little odd here...
> 
>> --- a/drivers/scsi/scsi_pm.c
>> +++ b/drivers/scsi/scsi_pm.c
>> @@ -144,33 +144,78 @@ static int scsi_bus_restore(struct device *dev)
>>  
>>  #ifdef CONFIG_PM_RUNTIME
>>  
>> +static int sdev_blk_runtime_suspend(struct scsi_device *sdev,
>> +					int (*cb)(struct device *))
>> +{
>> +	int err;
>> +
>> +	err = blk_pre_runtime_suspend(sdev->request_queue);
>> +	if (err)
>> +		return err;
>> +	if (cb)
>> +		err = cb(&sdev->sdev_gendev);
>> +	blk_post_runtime_suspend(sdev->request_queue, err);
>> +
>> +	return err;
>> +}
>> +
>> +static int sdev_runtime_suspend(struct device *dev)
>> +{
>> +	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
>> +	int (*cb)(struct device *) = pm ? pm->runtime_suspend : NULL;
>> +	struct scsi_device *sdev = to_scsi_device(dev);
>> +
>> +	if (sdev->request_queue->dev)
>> +		return sdev_blk_runtime_suspend(sdev, cb);
>> +	else
>> +		return scsi_dev_type_suspend(dev, cb);
>> +}
>> +
>>  static int scsi_runtime_suspend(struct device *dev)
>>  {
>>  	int err = 0;
>> -	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
>>  
>>  	dev_dbg(dev, "scsi_runtime_suspend\n");
>> -	if (scsi_is_sdev_device(dev)) {
>> -		err = scsi_dev_type_suspend(dev,
>> -				pm ? pm->runtime_suspend : NULL);
>> -		if (err == -EAGAIN)
>> -			pm_schedule_suspend(dev, jiffies_to_msecs(
>> -				round_jiffies_up_relative(HZ/10)));
>> -	}
>> +	if (scsi_is_sdev_device(dev))
>> +		err = sdev_runtime_suspend(dev);
> 
> The "if (err == -EAGAIN)" test and the call to pm_schedule_suspend seem
> to have been dropped since v8 of this series.  It looks like they ought
> to be moved into sdev_runtime_suspend.

I thought they were no longer needed...

For sd, we have request based rutime PM and the PM core will always try
to autosuspend the device with the timer; and for sr, the poll will
trigger suspend constantly. And for both, we don't return -EAGAIN anyway.
So I suppose that code is not necessary?

BTW, I'll be on vocation till 02/17, and I don't have access to the
internet in my hometown, but please feel free to drop any comments and
I'll check them when I get back.

Thanks,
Aaron

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