Commit 0b257734 authored Nov 23, 2016 by Subhash Jadavani Committed by Martin K. Petersen Nov 29, 2016

scsi: ufs: optimize system suspend handling



Consider following sequence of events:
1. UFS is runtime suspended, link_state = Hibern8, device_state = sleep
2. System goes into system suspend, ufshcd_system_suspend() brings both
   link and device to active state and then puts the device in Power_Down
   state and link in OFF state.
3. System resumes at some later point in time, ufshcd_system_resume()
   doesn't do anything as UFS state is runtime suspended. Note that link
   is still on OFF state and device is in Power_Down state.
4. Now system again goes into suspend without any UFS accesses before it.
   ufshcd_system_suspend() again brings both link and device to active
   state and then puts the device in Power_Down state and link if OFF
   state. But it's unnecessary to bring the link & device in active state
   as both link and device are already in desired low power states. This
   change fixes this issue by adding proper state checks in
   ufshcd_system_suspend().

Reviewed-by: Gilad Broner <gbroner@codeaurora.org>
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

parent f37e9f8c

drivers/scsi/ufs/ufshcd.c

+6 −9

Original line number	Diff line number	Diff line
		@@ -6272,16 +6272,13 @@ int ufshcd_system_suspend(struct ufs_hba *hba)
		if (!hba \|\| !hba->is_powered)
		return 0;

		if (pm_runtime_suspended(hba->dev)) {
		if (hba->rpm_lvl == hba->spm_lvl)
		/*
		* There is possibility that device may still be in
		* active state during the runtime suspend.
		*/
		if ((ufs_get_pm_lvl_to_dev_pwr_mode(hba->spm_lvl) ==
		hba->curr_dev_pwr_mode) && !hba->auto_bkops_enabled)
		hba->curr_dev_pwr_mode) &&
		(ufs_get_pm_lvl_to_link_pwr_state(hba->spm_lvl) ==
		hba->uic_link_state))
		goto out;

		if (pm_runtime_suspended(hba->dev)) {
		/*
		* UFS device and/or UFS link low power states during runtime
		* suspend seems to be different than what is expected during