From 28fd00d42cca178638f51c08efa986a777c24a4b Mon Sep 17 00:00:00 2001 From: Lin Ming Date: Thu, 22 Dec 2011 14:50:47 +0800 Subject: [PATCH] [SCSI] runtime resume parent for child's system-resume [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. Acked-by: Alan Stern Signed-off-by: Lin Ming Signed-off-by: Jeff Garzik --- drivers/scsi/scsi_pm.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/drivers/scsi/scsi_pm.c b/drivers/scsi/scsi_pm.c index a633076e5622..bf8bf79e6a1f 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); -- GitLab