scsi: ufs: optimize system suspend handling

This change “scsi: ufs: optimize system suspend handling” (commit 0b25773) in Linux kernel is authored by subhashj [at] codeaurora.org <subhashj [at] codeaurora.org> on Wed Nov 23 16:33:08 2016 -0800.

Description of "scsi: ufs: optimize system suspend handling"

The change “scsi: ufs: optimize system suspend handling” introduces changes as follows.

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>

Linux kernel releases containing commit 0b25773

The Linux kernel releases containing this commit are as follows.

Linux kernel code changes from "scsi: ufs: optimize system suspend handling"

There are 15 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 drivers/scsi/ufs/ufshcd.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)
 
diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index b82607856607..4b6cc0773681 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -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)
-				goto out;
+	if ((ufs_get_pm_lvl_to_dev_pwr_mode(hba->spm_lvl) ==
+	     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

The commit for this change in Linux stable tree is 0b25773 (patch).

Last modified: 2020/02/09