scsi: ufs: Add quirk to disallow reset of interrupt aggregation

Some host controllers support interrupt aggregation but don't allow
resetting counter and timer in software.

Link: https://lore.kernel.org/r/20200528011658.71590-3-alim.akhtar@samsung.comReviewed-by: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Seungwon Jeon <essuuj@gmail.com>
Signed-off-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/ufs/ufshcd.c

@@ -4909,7 +4909,8 @@ static irqreturn_t ufshcd_transfer_req_compl(struct ufs_hba *hba)
 	 * false interrupt if device completes another request after resetting
 	 * aggregation and before reading the DB.
 	 */
-	if (ufshcd_is_intr_aggr_allowed(hba))
+	if (ufshcd_is_intr_aggr_allowed(hba) &&
+	    !(hba->quirks & UFSHCI_QUIRK_SKIP_RESET_INTR_AGGR))
 		ufshcd_reset_intr_aggr(hba);
 
 	tr_doorbell = ufshcd_readl(hba, REG_UTP_TRANSFER_REQ_DOOR_BELL);

drivers/scsi/ufs/ufshcd.h

@@ -525,6 +525,12 @@ enum ufshcd_quirks {
 	 * Clear handling for transfer/task request list is just opposite.
 	 */
 	UFSHCI_QUIRK_BROKEN_REQ_LIST_CLR		= 1 << 6,
+
+	/*
+	 * This quirk needs to be enabled if host controller doesn't allow
+	 * that the interrupt aggregation timer and counter are reset by s/w.
+	 */
+	UFSHCI_QUIRK_SKIP_RESET_INTR_AGGR		= 1 << 7,
 };
 
 enum ufshcd_caps {