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SubjectRe: [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@intel.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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