[PATCH v2 2/5] scsi: ufs: core: Introduce ufshcd_rpm_resume_and_get() helper

[Stanley Jhu <stanleyjhu@google.com>]

ufshcd_clkscale_enable_store() and ufshcd_auto_hibern8_update() resume
the UFS device W-LUN with ufshcd_rpm_get_sync() and ignore its return
value.

For clkscale_enable:

1. The W-LUN is runtime suspended and clock scaling is disabled.
2. User space writes 1 to clkscale_enable.
3. ufshcd_clkscale_enable_store() calls ufshcd_rpm_get_sync().
4. The W-LUN runtime resume fails and the W-LUN stays suspended.
5. ufshcd_rpm_get_sync() returns a negative errno, which is ignored.
6. ufshcd_clkscale_enable_store() enables clock scaling and resumes
   devfreq while the W-LUN is still suspended.

For auto_hibern8:

1. The W-LUN starts a runtime suspend.
2. User space writes a new value to auto_hibern8.
3. ufshcd_auto_hibern8_update() sees that the W-LUN is not yet
   suspended and calls ufshcd_rpm_get_sync().
4. ufshcd_rpm_get_sync() waits for the runtime suspend to finish and
   then runs the W-LUN runtime resume.
5. The W-LUN runtime resume fails and the W-LUN stays suspended.
6. ufshcd_rpm_get_sync() returns a negative errno, which is ignored.
7. ufshcd_auto_hibern8_update() writes REG_AUTO_HIBERNATE_IDLE_TIMER
   while the W-LUN is still suspended.

Add ufshcd_rpm_resume_and_get() wrapping pm_runtime_resume_and_get() so
failed resumes drop the usage reference automatically, and return early
in ufshcd_clkscale_enable_store() and ufshcd_auto_hibern8_update() when
it fails.

Fixes: b294ff3e3449 ("scsi: ufs: core: Enable power management for wlun")
Cc: stable@vger.kernel.org
Signed-off-by: Stanley Jhu <stanleyjhu@google.com>
---
 drivers/ufs/core/ufshcd-priv.h | 5 +++++
 drivers/ufs/core/ufshcd.c      | 7 +++++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/ufs/core/ufshcd-priv.h b/drivers/ufs/core/ufshcd-priv.h
index e55c2a02c1f5..99f654b79035 100644
--- a/drivers/ufs/core/ufshcd-priv.h
+++ b/drivers/ufs/core/ufshcd-priv.h
@@ -388,6 +388,11 @@ static inline int ufshcd_rpm_get_sync(struct ufs_hba *hba)
 	return pm_runtime_get_sync(&hba->ufs_device_wlun->sdev_gendev);
 }
 
+static inline int ufshcd_rpm_resume_and_get(struct ufs_hba *hba)
+{
+	return pm_runtime_resume_and_get(&hba->ufs_device_wlun->sdev_gendev);
+}
+
 static inline int ufshcd_rpm_get_if_active(struct ufs_hba *hba)
 {
 	return pm_runtime_get_if_active(&hba->ufs_device_wlun->sdev_gendev);
diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
index 68a98cde5812..5972e85d279e 100644
--- a/drivers/ufs/core/ufshcd.c
+++ b/drivers/ufs/core/ufshcd.c
@@ -1864,7 +1864,9 @@ static ssize_t ufshcd_clkscale_enable_store(struct device *dev,
 	if (value == hba->clk_scaling.is_enabled)
 		goto out;
 
-	ufshcd_rpm_get_sync(hba);
+	err = ufshcd_rpm_resume_and_get(hba);
+	if (err)
+		goto out;
 	ufshcd_hold(hba);
 
 	hba->clk_scaling.is_enabled = value;
@@ -4792,7 +4794,8 @@ void ufshcd_auto_hibern8_update(struct ufs_hba *hba, u32 ahit)
 
 	WRITE_ONCE(hba->ahit, ahit);
 	if (!pm_runtime_suspended(&hba->ufs_device_wlun->sdev_gendev)) {
-		ufshcd_rpm_get_sync(hba);
+		if (ufshcd_rpm_resume_and_get(hba))
+			return;
 		ufshcd_hold(hba);
 		/*
 		 * Serialize with the host driver's AHIT control. Skip the
-- 
2.56.0.313.g2479322e68-goog