scsi: ufs-mediatek: Introduce low-power mode for device power supply

Allow device power supply to enter low-power mode.

Link: https://lore.kernel.org/r/20200601104646.15436-4-stanley.chu@mediatek.comReviewed-by: Pengshun Zhao <pengshun.zhao@mediatek.com>
Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/ufs/ufs-mediatek.c

@@ -12,6 +12,7 @@
 #include <linux/of_address.h>
 #include <linux/phy/phy.h>
 #include <linux/platform_device.h>
+#include <linux/regulator/consumer.h>
 #include <linux/soc/mediatek/mtk_sip_svc.h>
 
 #include "ufshcd.h"
@@ -521,6 +522,19 @@ static int ufs_mtk_link_set_lpm(struct ufs_hba *hba)
 	return 0;
 }
 
+static void ufs_mtk_vreg_set_lpm(struct ufs_hba *hba, bool lpm)
+{
+	if (!hba->vreg_info.vccq2)
+		return;
+
+	if (lpm & !hba->vreg_info.vcc->enabled)
+		regulator_set_mode(hba->vreg_info.vccq2->reg,
+				   REGULATOR_MODE_IDLE);
+	else if (!lpm)
+		regulator_set_mode(hba->vreg_info.vccq2->reg,
+				   REGULATOR_MODE_NORMAL);
+}
+
 static int ufs_mtk_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 {
 	int err;
@@ -537,6 +551,12 @@ static int ufs_mtk_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 			ufshcd_set_link_off(hba);
 			return -EAGAIN;
 		}
+		/*
+		 * Make sure no error will be returned to prevent
+		 * ufshcd_suspend() re-enabling regulators while vreg is still
+		 * in low-power mode.
+		 */
+		ufs_mtk_vreg_set_lpm(hba, true);
 	}
 
 	if (!ufshcd_is_link_active(hba))
@@ -554,6 +574,7 @@ static int ufs_mtk_resume(struct ufs_hba *hba, enum ufs_pm_op pm_op)
 		phy_power_on(host->mphy);
 
 	if (ufshcd_is_link_hibern8(hba)) {
+		ufs_mtk_vreg_set_lpm(hba, false);
 		err = ufs_mtk_link_set_hpm(hba);
 		if (err) {
 			err = ufshcd_link_recovery(hba);