[PATCH v1 2/2] scsi: ufs: Support reading UFS's Vcc voltage from device tree

[Bao D. Nguyen]

The UFS specifications supports a range of Vcc operating voltage
from 2.4-3.6V depending on the device and manufacturers.
Allows selecting the UFS Vcc voltage level by setting the
UFS's entry vcc-voltage-level in the device tree. If UFS's
vcc-voltage-level setting is not found in the device tree,
use default values provided by the driver.

Signed-off-by: Can Guo <cang@xxxxxxxxxxxxxx>
Signed-off-by: Asutosh Das <asutoshd@xxxxxxxxxxxxxx>
Signed-off-by: Bao D. Nguyen <nguyenb@xxxxxxxxxxxxxx>
---
 drivers/scsi/ufs/ufshcd-pltfrm.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/ufs/ufshcd-pltfrm.c b/drivers/scsi/ufs/ufshcd-pltfrm.c
index 3db0af6..48f429c 100644
--- a/drivers/scsi/ufs/ufshcd-pltfrm.c
+++ b/drivers/scsi/ufs/ufshcd-pltfrm.c
@@ -104,10 +104,11 @@ static int ufshcd_parse_clock_info(struct ufs_hba *hba)
 static int ufshcd_populate_vreg(struct device *dev, const char *name,
 		struct ufs_vreg **out_vreg)
 {
-	int ret = 0;
+	int len, ret = 0;
 	char prop_name[MAX_PROP_SIZE];
 	struct ufs_vreg *vreg = NULL;
 	struct device_node *np = dev->of_node;
+	const __be32 *prop;
 
 	if (!np) {
 		dev_err(dev, "%s: non DT initialization\n", __func__);
@@ -138,8 +139,16 @@ static int ufshcd_populate_vreg(struct device *dev, const char *name,
 			vreg->min_uV = UFS_VREG_VCC_1P8_MIN_UV;
 			vreg->max_uV = UFS_VREG_VCC_1P8_MAX_UV;
 		} else {
-			vreg->min_uV = UFS_VREG_VCC_MIN_UV;
-			vreg->max_uV = UFS_VREG_VCC_MAX_UV;
+			prop = of_get_property(np, "vcc-voltage-level", &len);
+			if (!prop || (len != (2 * sizeof(__be32)))) {
+				dev_warn(dev, "%s vcc-voltage-level property.\n",
+					prop ? "invalid format" : "no");
+				vreg->min_uV = UFS_VREG_VCC_MIN_UV;
+				vreg->max_uV = UFS_VREG_VCC_MAX_UV;
+			} else {
+				vreg->min_uV = be32_to_cpup(&prop[0]);
+				vreg->max_uV = be32_to_cpup(&prop[1]);
+			}
 		}
 	} else if (!strcmp(name, "vccq")) {
 		vreg->min_uV = UFS_VREG_VCCQ_MIN_UV;
-- 
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