scsi: ufs: ufs-mediatek: Prevent host hang by setting CLK_CG early

Some UFSHCI hosts in MediaTek UFS platform need workaround to prevent host
hang issue by setting CLK_CG bit before host is enabled.

This operation shall have no side effect on those platforms which do not
support this bit.

Link: https://lore.kernel.org/r/20220623035052.18802-4-stanley.chu@mediatek.com
Reviewed-by: Stanley Chu <stanley.chu@mediatek.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Peter Wang <peter.wang@mediatek.com>
Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/ufs/host/ufs-mediatek.c

@@ -183,6 +183,14 @@ static int ufs_mtk_hce_enable_notify(struct ufs_hba *hba,
 			hba->capabilities &= ~MASK_AUTO_HIBERN8_SUPPORT;
 			hba->ahit = 0;
 		}
+
+		/*
+		 * Turn on CLK_CG early to bypass abnormal ERR_CHK signal
+		 * to prevent host hang issue
+		 */
+		ufshcd_writel(hba,
+			      ufshcd_readl(hba, REG_UFS_XOUFS_CTRL) | 0x80,
+			      REG_UFS_XOUFS_CTRL);
 	}
 
 	return 0;

drivers/ufs/host/ufs-mediatek.h

@@ -12,6 +12,7 @@
 /*
  * Vendor specific UFSHCI Registers
  */
+#define REG_UFS_XOUFS_CTRL          0x140
 #define REG_UFS_REFCLK_CTRL         0x144
 #define REG_UFS_EXTREG              0x2100
 #define REG_UFS_MPHYCTRL            0x2200