On Fri, 25 Nov 2011, Lin Ming wrote:
> Below is the updated patch with your suggested patch description and
> comments.
>
> Looks OK?
>
> Subject: [PATCH] [SCSI] check runtime PM status in system PM
>
> The only high-level SCSI driver that currently implements runtime PM is
> sd, and sd treats runtime suspend exactly the same as the SUSPEND and
> HIBERNATE stages of system sleep, but not the same as the FREEZE stage.
>
> Therefore, when entering the SUSPEND or HIBERNATE stages of system
> sleep, we can skip the callback to the driver if the device is already
> in runtime suspend. When entering the FREEZE stage, however, we should
> first issue a runtime resume. The overhead of doing this is
> negligible, because a suspended drive would be spun up during the THAW
> stage of hibernation anyway.
>
> Signed-off-by: Lin Ming <ming.m.lin@xxxxxxxxx>
> ---
> drivers/scsi/scsi_pm.c | 16 +++++++++++++++-
> 1 files changed, 15 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/scsi/scsi_pm.c b/drivers/scsi/scsi_pm.c
> index d329f8b..a633076 100644
> --- a/drivers/scsi/scsi_pm.c
> +++ b/drivers/scsi/scsi_pm.c
> @@ -49,8 +49,22 @@ static int scsi_bus_suspend_common(struct device *dev, pm_message_t msg)
> {
> int err = 0;
>
> - if (scsi_is_sdev_device(dev))
> + if (scsi_is_sdev_device(dev)) {
> + /*
> + * sd is the only high-level SCSI driver to implement runtime
> + * PM, and sd treats runtime suspend, system suspend, and
> + * system hibernate identically (but not system freeze).
> + */
> + if (pm_runtime_suspended(dev)) {
> + if (msg.event == PM_EVENT_SUSPEND ||
> + msg.event == PM_EVENT_HIBERNATE)
> + return 0; /* already suspended */
> +
> + /* wake up device so that FREEZE will succeed */
> + pm_runtime_resume(dev);
> + }
> err = scsi_dev_type_suspend(dev, msg);
> + }
> return err;
> }
This looks good to me.
Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
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