[PATCH] scsi: ufs: read door bell register after clearing interrupt aggregation

[Dolev Raviv]

In interrupt context, after reading and comparing the UTRLDBR to
hba->outstanding_request and before resetting the interrupt aggregation,
there might be completion of another transfer request (TR). Such TRs might
get stuck, pending, until the next interrupt is generated.

The fix reads the UTRLDBR after resetting the interrupt aggregation and
handles completed TRs.

Signed-off-by: Dolev Raviv <draviv@xxxxxxxxxxxxxx>

diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
index 4dca9b4..30c84d8 100644
--- a/drivers/scsi/ufs/ufshcd.c
+++ b/drivers/scsi/ufs/ufshcd.c
@@ -1915,6 +1915,13 @@ static void ufshcd_uic_cmd_compl(struct ufs_hba *hba)
 /**
  * ufshcd_transfer_req_compl - handle SCSI and query command completion
  * @hba: per adapter instance
+ *
+ * Resetting interrupt aggregation counters first and reading the DOOR_BELL
+ * afterward , allows us to handle all the completed requests.
+ * In order to prevent other interrupts starvation the DB is read once
+ * after reset. The down side of this solution is the possibility of false
+ * interrupt if device completes another request after resetting aggregation
+ * and before reading the DB.
  */
 static void ufshcd_transfer_req_compl(struct ufs_hba *hba)
 {
@@ -1924,47 +1931,36 @@ static void ufshcd_transfer_req_compl(struct ufs_hba *hba)
 	u32 tr_doorbell;
 	int result;
 	int index;
-	bool int_aggr_reset = false;
+
+	/* Reset interrupt aggregation counters */
+	ufshcd_config_int_aggr(hba, INT_AGGR_RESET);
 
 	tr_doorbell = ufshcd_readl(hba, REG_UTP_TRANSFER_REQ_DOOR_BELL);
 	completed_reqs = tr_doorbell ^ hba->outstanding_reqs;
 
-	for (index = 0; index < hba->nutrs; index++) {
-		if (test_bit(index, &completed_reqs)) {
-			lrbp = &hba->lrb[index];
-			cmd = lrbp->cmd;
-			/*
-			 * Don't skip resetting interrupt aggregation counters
-			 * if a regular command is present.
-			 */
-			int_aggr_reset |= !lrbp->intr_cmd;
-
-			if (cmd) {
-				result = ufshcd_transfer_rsp_status(hba, lrbp);
-				scsi_dma_unmap(cmd);
-				cmd->result = result;
-				/* Mark completed command as NULL in LRB */
-				lrbp->cmd = NULL;
-				clear_bit_unlock(index, &hba->lrb_in_use);
-				/* Do not touch lrbp after scsi done */
-				cmd->scsi_done(cmd);
-			} else if (lrbp->command_type ==
-					UTP_CMD_TYPE_DEV_MANAGE) {
-				if (hba->dev_cmd.complete)
-					complete(hba->dev_cmd.complete);
-			}
-		} /* end of if */
-	} /* end of for */
+	for_each_set_bit(index, &completed_reqs, hba->nutrs) {
+		lrbp = &hba->lrb[index];
+		cmd = lrbp->cmd;
+		if (cmd) {
+			result = ufshcd_transfer_rsp_status(hba, lrbp);
+			scsi_dma_unmap(cmd);
+			cmd->result = result;
+			/* Mark completed command as NULL in LRB */
+			lrbp->cmd = NULL;
+			clear_bit_unlock(index, &hba->lrb_in_use);
+			/* Do not touch lrbp after scsi done */
+			cmd->scsi_done(cmd);
+		} else if (lrbp->command_type == UTP_CMD_TYPE_DEV_MANAGE) {
+			if (hba->dev_cmd.complete)
+				complete(hba->dev_cmd.complete);
+		}
+	} /* end of for_each_set_bit */
 
 	/* clear corresponding bits of completed commands */
 	hba->outstanding_reqs ^= completed_reqs;
 
 	/* we might have free'd some tags above */
 	wake_up(&hba->dev_cmd.tag_wq);
-
-	/* Reset interrupt aggregation counters */
-	if (int_aggr_reset)
-		ufshcd_config_int_aggr(hba, INT_AGGR_RESET);
 }
 
 /**
@@ -2569,6 +2565,7 @@ static int ufshcd_abort(struct scsi_cmnd *cmd)
 	int poll_cnt;
 	u8 resp = 0xF;
 	struct ufshcd_lrb *lrbp;
+	u32 reg;
 
 	host = cmd->device->host;
 	hba = shost_priv(host);
@@ -2578,6 +2575,13 @@ static int ufshcd_abort(struct scsi_cmnd *cmd)
 	if (!(test_bit(tag, &hba->outstanding_reqs)))
 		goto out;
 
+	reg = ufshcd_readl(hba, REG_UTP_TRANSFER_REQ_DOOR_BELL);
+	if (!(reg & (1 << tag))) {
+		dev_err(hba->dev,
+		"%s: cmd was completed, but without a notifying intr, tag = %d",
+		__func__, tag);
+	}
+
 	lrbp = &hba->lrb[tag];
 	for (poll_cnt = 100; poll_cnt; poll_cnt--) {
 		err = ufshcd_issue_tm_cmd(hba, lrbp->lun, lrbp->task_tag,
@@ -2586,8 +2590,6 @@ static int ufshcd_abort(struct scsi_cmnd *cmd)
 			/* cmd pending in the device */
 			break;
 		} else if (!err && resp == UPIU_TASK_MANAGEMENT_FUNC_COMPL) {
-			u32 reg;
-
 			/*
 			 * cmd not pending in the device, check if it is
 			 * in transition.
-- 
1.7.6
-- 
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