On Wed, Dec 14, 2011 at 11:18 AM, Lin Ming <ming.m.lin@xxxxxxxxx> wrote:
> [Patch description from Alan Stern]
>
> If a child device was runtime-suspended when a system suspend began,
> then there will be nothing to prevent its parent from
> runtime-suspending as soon as it is woken up during the system resume.
> Then when the time comes to resume the child, the resume will fail
> because the parent is already back at low power.
>
> On the other hand, there are some devices which should remain at low
> power across an entire suspend-resume cycle. The details depend on the
> device and the platform.
>
> This suggests that the PM core is not the right place to solve the
> problem. One possible solution is for the subsystem or device driver
> to call pm_runtime_get_sync(dev->parent) at the start of the
> system-resume procedure and pm_runtime_put_sync(dev->parent) at the
> end.
>
> Signed-off-by: Lin Ming <ming.m.lin@xxxxxxxxx>
Hi Alan,
May I add your SOB?
Thanks,
Lin Ming
> ---
> drivers/scsi/scsi_pm.c | 11 ++++++++++-
> 1 files changed, 10 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/scsi/scsi_pm.c b/drivers/scsi/scsi_pm.c
> index a633076..bf8bf79 100644
> --- a/drivers/scsi/scsi_pm.c
> +++ b/drivers/scsi/scsi_pm.c
> @@ -72,8 +72,17 @@ static int scsi_bus_resume_common(struct device *dev)
> {
> int err = 0;
>
> - if (scsi_is_sdev_device(dev))
> + if (scsi_is_sdev_device(dev)) {
> + /*
> + * Parent device may have runtime suspended as soon as
> + * it is woken up during the system resume.
> + *
> + * Resume it on behalf of child.
> + */
> + pm_runtime_get_sync(dev->parent);
> err = scsi_dev_type_resume(dev);
> + pm_runtime_put_sync(dev->parent);
> + }
>
> if (err == 0) {
> pm_runtime_disable(dev);
> --
> 1.7.2.5
>
> --
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