[PATCH v10 3/4] scsi: ufs: core: Make ufshcd_wl_poweroff() behave like ufshcd_wl_suspend()

[HOYOUNG SEO]

ufshcd_wl_poweroff(), the hibernation poweroff callback, calls
__ufshcd_wl_suspend(hba, UFS_SHUTDOWN_PM) directly and ignores the
result. Unlike ufshcd_wl_suspend() it:

 - does not take hba->host_sem. An error handler that runs in the
   meantime can reset the link concurrently with __ufshcd_wl_suspend().
   It also leaves host_sem unbalanced: if hibernation is aborted after
   ufshcd_wl_poweroff() has been called, ufshcd_wl_resume() is called as
   the .restore callback and releases host_sem, which was not acquired;
 - does not check pm_runtime_suspended(dev). __ufshcd_suspend_prepare()
   leaves the WLUN runtime suspended if ufshcd_rpm_ok_for_spm() is true,
   which is the case if rpm_lvl and spm_lvl are equal. Then
   __ufshcd_wl_suspend() triggers error recovery and returns -EBUSY;
 - does not set hba->is_sys_suspended, so ufshcd_err_handling_prepare()
   does not restore the clocks and regulators if the .restore callback
   fails;
 - ignores errors.

Call ufshcd_wl_system_suspend() with UFS_SHUTDOWN_PM from
ufshcd_wl_poweroff() to fix all of these, as suggested by Bart Van
Assche. host_sem is held until ufshcd_wl_resume() releases it if
hibernation is aborted, and released if the suspend fails. For
UFS_SHUTDOWN_PM, __ufshcd_wl_suspend() does not convert failures into
-EBUSY, so a positive SCSI or UIC status can be returned. A dev_pm_ops
callback has to return a negative error code, so convert it.

This changes the behavior of ufshcd_wl_poweroff(): an error is now
returned from the .poweroff callback, which aborts hibernation, instead
of being ignored, and a runtime suspended WLUN is left as it is like in
ufshcd_wl_suspend().

Do not use hba->shutting_down to stop the error handler: it makes
ufs_mtk_system_suspend(), which is also the .poweroff callback of the
MediaTek host controller, fail with -EBUSY, and nothing clears it when
hibernation is aborted.

Fixes: b294ff3e3449 ("scsi: ufs: core: Enable power management for wlun")
Suggested-by: Bart Van Assche <bvanassche@xxxxxxx>
Signed-off-by: HOYOUNG SEO <hy50.seo@xxxxxxxxxxx>
---
 drivers/ufs/core/ufshcd.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 4825349e87fd..8aea99f5c364 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -10729,6 +10729,9 @@ static int ufshcd_wl_system_suspend(struct device *dev, enum ufs_pm_op pm_op)
 	if (ret) {
 		dev_err(&sdev->sdev_gendev, "%s failed: %d\n", __func__,  ret);
 		up(&hba->host_sem);
+		/* __ufshcd_wl_suspend() can return a positive status for UFS_SHUTDOWN_PM. */
+		if (ret > 0)
+			ret = -EBUSY;
 	}
 
 out:
@@ -11576,11 +11579,7 @@ EXPORT_SYMBOL_GPL(ufshcd_suspend_prepare);
 #ifdef CONFIG_PM_SLEEP
 static int ufshcd_wl_poweroff(struct device *dev)
 {
-	struct scsi_device *sdev = to_scsi_device(dev);
-	struct ufs_hba *hba = shost_priv(sdev->host);
-
-	__ufshcd_wl_suspend(hba, UFS_SHUTDOWN_PM);
-	return 0;
+	return ufshcd_wl_system_suspend(dev, UFS_SHUTDOWN_PM);
 }
 #endif
 
-- 
2.34.1