scsi: ufs: fix Auto-Hibern8 error detection

Auto-Hibern8 may be disabled by some vendors or sysfs in runtime even if
Auto-Hibern8 capability is supported by host. If Auto-Hibern8 capability is
supported by host but not actually enabled, Auto-Hibern8 error shall not
happen.

To fix this, provide a way to detect if Auto-Hibern8 is actually enabled
first, and bypass Auto-Hibern8 disabling case in
ufshcd_is_auto_hibern8_error().

Fixes: 82174440 ("scsi: ufs: Add error-handling of Auto-Hibernate")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20200129105251.12466-4-stanley.chu@mediatek.comReviewed-by: Bean Huo <beanhuo@micron.com>
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Reviewed-by: Asutosh Das <asutoshd@codeaurora.org>
Reviewed-by: Can Guo <cang@codeaurora.org>
Signed-off-by: Stanley Chu <stanley.chu@mediatek.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/ufs/ufshcd.c

@@ -5479,7 +5479,8 @@ static irqreturn_t ufshcd_update_uic_error(struct ufs_hba *hba)
 static bool ufshcd_is_auto_hibern8_error(struct ufs_hba *hba,
 					 u32 intr_mask)
 {
-	if (!ufshcd_is_auto_hibern8_supported(hba))
+	if (!ufshcd_is_auto_hibern8_supported(hba) ||
+	    !ufshcd_is_auto_hibern8_enabled(hba))
 		return false;
 
 	if (!(intr_mask & UFSHCD_UIC_HIBERN8_MASK))

drivers/scsi/ufs/ufshcd.h

@@ -55,6 +55,7 @@
 #include <linux/clk.h>
 #include <linux/completion.h>
 #include <linux/regulator/consumer.h>
+#include <linux/bitfield.h>
 #include "unipro.h"
 
 #include <asm/irq.h>
@@ -773,6 +774,11 @@ static inline bool ufshcd_is_auto_hibern8_supported(struct ufs_hba *hba)
 	return (hba->capabilities & MASK_AUTO_HIBERN8_SUPPORT);
 }
 
+static inline bool ufshcd_is_auto_hibern8_enabled(struct ufs_hba *hba)
+{
+	return FIELD_GET(UFSHCI_AHIBERN8_TIMER_MASK, hba->ahit) ? true : false;
+}
+
 #define ufshcd_writel(hba, val, reg)	\
 	writel((val), (hba)->mmio_base + (reg))
 #define ufshcd_readl(hba, reg)	\