linux-kernel - [PATCH 01/10] i2c: xiic: Fix Tx Interrupt path for grouped messages

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Date:   Mon, 31 May 2021 07:19:39 -0600
From:   Raviteja Narayanam <raviteja.narayanam@...inx.com>
To:     <linux-i2c@...r.kernel.org>, <michal.simek@...inx.com>
CC:     <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <git@...inx.com>, <marex@...x.de>,
        Raviteja Narayanam <raviteja.narayanam@...inx.com>
Subject: [PATCH 01/10] i2c: xiic: Fix Tx Interrupt path for grouped messages

When a group of messages are sent from user space as a set, if
the last message has less than Tx FIFO DEPTH number of bytes
to transfer, Tx half empty interrupt is triggered continuously
from the hardware. It is due to Bus not busy interrupt coming
along with Tx half empty and tx empty.

Hence, service the Tx interrupts before Bus not busy interrupt
to update the i2c message status correctly.

Signed-off-by: Raviteja Narayanam <raviteja.narayanam@...inx.com>
---
 drivers/i2c/busses/i2c-xiic.c | 34 ++++++++++++++++++----------------
 1 file changed, 18 insertions(+), 16 deletions(-)

diff --git a/drivers/i2c/busses/i2c-xiic.c b/drivers/i2c/busses/i2c-xiic.c
index 2a8568b97c14..b0cfd9d15467 100644
--- a/drivers/i2c/busses/i2c-xiic.c
+++ b/drivers/i2c/busses/i2c-xiic.c
@@ -453,22 +453,6 @@ static irqreturn_t xiic_process(int irq, void *dev_id)
 			}
 		}
 	}
-	if (pend & XIIC_INTR_BNB_MASK) {
-		/* IIC bus has transitioned to not busy */
-		clr |= XIIC_INTR_BNB_MASK;
-
-		/* The bus is not busy, disable BusNotBusy interrupt */
-		xiic_irq_dis(i2c, XIIC_INTR_BNB_MASK);
-
-		if (!i2c->tx_msg)
-			goto out;
-
-		if ((i2c->nmsgs == 1) && !i2c->rx_msg &&
-			xiic_tx_space(i2c) == 0)
-			xiic_wakeup(i2c, STATE_DONE);
-		else
-			xiic_wakeup(i2c, STATE_ERROR);
-	}
 	if (pend & (XIIC_INTR_TX_EMPTY_MASK | XIIC_INTR_TX_HALF_MASK)) {
 		/* Transmit register/FIFO is empty or ½ empty */
 
@@ -505,6 +489,24 @@ static irqreturn_t xiic_process(int irq, void *dev_id)
 			 */
 			xiic_irq_dis(i2c, XIIC_INTR_TX_HALF_MASK);
 	}
+
+	if (pend & XIIC_INTR_BNB_MASK) {
+		/* IIC bus has transitioned to not busy */
+		clr |= XIIC_INTR_BNB_MASK;
+
+		/* The bus is not busy, disable BusNotBusy interrupt */
+		xiic_irq_dis(i2c, XIIC_INTR_BNB_MASK);
+
+		if (!i2c->tx_msg)
+			goto out;
+
+		if (i2c->nmsgs == 1 && !i2c->rx_msg &&
+		    xiic_tx_space(i2c) == 0)
+			xiic_wakeup(i2c, STATE_DONE);
+		else
+			xiic_wakeup(i2c, STATE_ERROR);
+	}
+
 out:
 	dev_dbg(i2c->adap.dev.parent, "%s clr: 0x%x\n", __func__, clr);
 
-- 
2.17.1