scsi: ufs-mediatek: Do not gate clocks if auto-hibern8 is not entered yet

There is a chance that link enters hibern8 via auto-hibern8 scheme during
the clock-gating flow. Clocks shall not be gated if link is still active
otherwise host or device may hang.

Fix this by returning error code to the caller __ufshcd_setup_clocks() to
skip gating clocks there if link is not confirmed in hibern8 state yet.

Also allow some waiting time for the hibern8 state transition.

Link: https://lore.kernel.org/r/20200601104646.15436-3-stanley.chu@mediatek.comReviewed-by: Andy Teng <andy.teng@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

@@ -178,15 +178,30 @@ static void ufs_mtk_setup_ref_clk_wait_us(struct ufs_hba *hba,
 	host->ref_clk_ungating_wait_us = ungating_us;
 }
 
-static u32 ufs_mtk_link_get_state(struct ufs_hba *hba)
+int ufs_mtk_wait_link_state(struct ufs_hba *hba, u32 state,
+			    unsigned long max_wait_ms)
 {
+	ktime_t timeout, time_checked;
 	u32 val;
 
-	ufshcd_writel(hba, 0x20, REG_UFS_DEBUG_SEL);
-	val = ufshcd_readl(hba, REG_UFS_PROBE);
-	val = val >> 28;
+	timeout = ktime_add_us(ktime_get(), ms_to_ktime(max_wait_ms));
+	do {
+		time_checked = ktime_get();
+		ufshcd_writel(hba, 0x20, REG_UFS_DEBUG_SEL);
+		val = ufshcd_readl(hba, REG_UFS_PROBE);
+		val = val >> 28;
+
+		if (val == state)
+			return 0;
 
-	return val;
+		/* Sleep for max. 200us */
+		usleep_range(100, 200);
+	} while (ktime_before(time_checked, timeout));
+
+	if (val == state)
+		return 0;
+
+	return -ETIMEDOUT;
 }
 
 /**
@@ -221,10 +236,13 @@ static int ufs_mtk_setup_clocks(struct ufs_hba *hba, bool on,
 			 * triggered by Auto-Hibern8.
 			 */
 			if (!ufshcd_can_hibern8_during_gating(hba) &&
-			    ufshcd_is_auto_hibern8_enabled(hba) &&
-			    ufs_mtk_link_get_state(hba) ==
-			    VS_LINK_HIBERN8)
-				ufs_mtk_setup_ref_clk(hba, on);
+			    ufshcd_is_auto_hibern8_enabled(hba)) {
+				ret = ufs_mtk_wait_link_state(hba,
+							      VS_LINK_HIBERN8,
+							      15);
+				if (!ret)
+					ufs_mtk_setup_ref_clk(hba, on);
+			}
 		}
 	} else if (on && status == POST_CHANGE) {
 		ret = phy_power_on(host->mphy);