[PATCH V4 3/4] scsi: ufs: core Enforce minimum pm level for sysfs configuration

[Ram Kumar Dwivedi <ram.dwivedi@oss.qualcomm.com>]

Some UFS platforms only support a limited subset of power levels.
Currently, the sysfs interface allows users to set any pm level
without validating the minimum supported value. If an unsupported
level is selected, suspend may fail.

Introduce an pm_lvl_min field in the ufs_hba structure and use it
to clamp the pm level requested via sysfs so that only supported
levels are accepted. Platforms that require a minimum pm level
can set this field during probe.

Signed-off-by: Ram Kumar Dwivedi <ram.dwivedi@oss.qualcomm.com>
---
 drivers/ufs/core/ufs-sysfs.c | 2 +-
 include/ufs/ufshcd.h         | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/ufs/core/ufs-sysfs.c b/drivers/ufs/core/ufs-sysfs.c
index b33f8656edb5..02e5468ad49d 100644
--- a/drivers/ufs/core/ufs-sysfs.c
+++ b/drivers/ufs/core/ufs-sysfs.c
@@ -141,7 +141,7 @@ static inline ssize_t ufs_sysfs_pm_lvl_store(struct device *dev,
 	if (kstrtoul(buf, 0, &value))
 		return -EINVAL;
 
-	if (value >= UFS_PM_LVL_MAX)
+	if (value >= UFS_PM_LVL_MAX || value < hba->pm_lvl_min)
 		return -EINVAL;
 
 	if (ufs_pm_lvl_states[value].dev_state == UFS_DEEPSLEEP_PWR_MODE &&
diff --git a/include/ufs/ufshcd.h b/include/ufs/ufshcd.h
index 19154228780b..ac8697a7355b 100644
--- a/include/ufs/ufshcd.h
+++ b/include/ufs/ufshcd.h
@@ -972,6 +972,7 @@ struct ufs_hba {
 	enum ufs_pm_level rpm_lvl;
 	/* Desired UFS power management level during system PM */
 	enum ufs_pm_level spm_lvl;
+	enum ufs_pm_level pm_lvl_min;
 	int pm_op_in_progress;
 
 	/* Auto-Hibernate Idle Timer register value */
-- 
2.34.1