[PATCH v9 2/3] scsi: ufs: core: Hold host_sem in ufshcd_wl_poweroff()

[HOYOUNG SEO <hy50.seo@samsung.com>]

ufshcd_wl_suspend() takes hba->host_sem and ufshcd_wl_resume() releases
it, which serializes the error handler against system suspend and
resume. ufshcd_wl_poweroff(), the hibernation poweroff callback, also
suspends the device with UFS_SHUTDOWN_PM but does not take 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.

Make ufshcd_wl_poweroff() behave like ufshcd_wl_suspend() and keep
holding host_sem. It is released by ufshcd_wl_resume() if hibernation is
aborted. If __ufshcd_wl_suspend() fails, release host_sem and return the
error as ufshcd_wl_suspend() does, otherwise the error handler, which
waits for host_sem, would block forever.

This changes the behavior on failure: the error is now returned from the
.poweroff callback, which aborts hibernation, instead of being ignored.

Do not use hba->shutting_down here: 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@acm.org>
Signed-off-by: HOYOUNG SEO <hy50.seo@samsung.com>
---
 drivers/ufs/core/ufshcd.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 3b5580ac390c..0d86c67f0b1a 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -11573,9 +11573,15 @@ static int ufshcd_wl_poweroff(struct device *dev)
 {
 	struct scsi_device *sdev = to_scsi_device(dev);
 	struct ufs_hba *hba = shost_priv(sdev->host);
+	int ret;
 
-	__ufshcd_wl_suspend(hba, UFS_SHUTDOWN_PM);
-	return 0;
+	/* Released by ufshcd_wl_resume() if hibernation is aborted. */
+	down(&hba->host_sem);
+	ret = __ufshcd_wl_suspend(hba, UFS_SHUTDOWN_PM);
+	if (ret)
+		up(&hba->host_sem);
+
+	return ret;
 }
 #endif
 
-- 
2.34.1