scsi: ufs: Introduce device quirk "DELAY_AFTER_LPM"

Some UFS devices require delay after VCC power rail is turned off.
Introduce a device quirk "DELAY_AFTER_LPM" to add 5ms delay after VCC
power-off during suspend flow.

Link: https://lore.kernel.org/r/20200729051840.31318-2-stanley.chu@mediatek.comReviewed-by: Andy Teng <andy.teng@mediatek.com>
Reviewed-by: Peter Wang <peter.wang@mediatek.com>
Reviewed-by: Can Guo <cang@codeaurora.org>
Acked-by: Avri Altman <Avri.Altman@wdc.com>
Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/ufs/ufs_quirks.h

@@ -109,4 +109,11 @@ struct ufs_dev_fix {
  */
 #define UFS_DEVICE_QUIRK_SUPPORT_EXTENDED_FEATURES (1 << 10)
 
+/*
+ * Some UFS devices require delay after VCC power rail is turned-off.
+ * Enable this quirk to introduce 5ms delays after VCC power-off during
+ * suspend flow.
+ */
+#define UFS_DEVICE_QUIRK_DELAY_AFTER_LPM        (1 << 11)
+
 #endif /* UFS_QUIRKS_H_ */

drivers/scsi/ufs/ufshcd.c

@@ -8107,6 +8107,8 @@ static int ufshcd_link_state_transition(struct ufs_hba *hba,
 
 static void ufshcd_vreg_set_lpm(struct ufs_hba *hba)
 {
+	bool vcc_off = false;
+
 	/*
 	 * It seems some UFS devices may keep drawing more than sleep current
 	 * (atleast for 500us) from UFS rails (especially from VCCQ rail).
@@ -8135,13 +8137,22 @@ static void ufshcd_vreg_set_lpm(struct ufs_hba *hba)
 	if (ufshcd_is_ufs_dev_poweroff(hba) && ufshcd_is_link_off(hba) &&
 	    !hba->dev_info.is_lu_power_on_wp) {
 		ufshcd_setup_vreg(hba, false);
+		vcc_off = true;
 	} else if (!ufshcd_is_ufs_dev_active(hba)) {
 		ufshcd_toggle_vreg(hba->dev, hba->vreg_info.vcc, false);
+		vcc_off = true;
 		if (!ufshcd_is_link_active(hba)) {
 			ufshcd_config_vreg_lpm(hba, hba->vreg_info.vccq);
 			ufshcd_config_vreg_lpm(hba, hba->vreg_info.vccq2);
 		}
 	}
+
+	/*
+	 * Some UFS devices require delay after VCC power rail is turned-off.
+	 */
+	if (vcc_off && hba->vreg_info.vcc &&
+		hba->dev_quirks & UFS_DEVICE_QUIRK_DELAY_AFTER_LPM)
+		usleep_range(5000, 5100);
 }
 
 static int ufshcd_vreg_set_hpm(struct ufs_hba *hba)