linux-kernel - [PATCH] i2c: imx-lpi2c: directly return ISR when detect a NACK

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Message-Id: <20230524024002.1790405-1-carlos.song@nxp.com>
Date:   Wed, 24 May 2023 10:40:02 +0800
From:   carlos.song@....com
To:     aisheng.dong@....com, shawnguo@...nel.org, s.hauer@...gutronix.de,
        kernel@...gutronix.de, festevam@...il.com
Cc:     carlos.song@....com, xiaoning.wang@....com, haibo.chen@....com,
        linux-imx@....com, linux-i2c@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] i2c: imx-lpi2c: directly return ISR when detect a NACK

From: Gao Pan <pandy.gao@....com>

A NACK flag in ISR means i2c bus error. In such codition,
there is no need to do read/write operation. It's better
to return ISR directly and then stop i2c transfer.

Fixes: a55fa9d0e42e ("i2c: imx-lpi2c: add low power i2c bus driver")
Signed-off-by: Gao Pan <pandy.gao@....com>
Signed-off-by: Carlos Song <carlos.song@....com>
---
 drivers/i2c/busses/i2c-imx-lpi2c.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c b/drivers/i2c/busses/i2c-imx-lpi2c.c
index 1af0a637d7f1..11240bf8e8e2 100644
--- a/drivers/i2c/busses/i2c-imx-lpi2c.c
+++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
@@ -514,15 +514,17 @@ static irqreturn_t lpi2c_imx_isr(int irq, void *dev_id)
 	temp = readl(lpi2c_imx->base + LPI2C_MSR);
 	temp &= enabled;
 
+	if (temp & MSR_NDF) {
+		complete(&lpi2c_imx->complete);
+		goto ret;
+	}
+
 	if (temp & MSR_RDF)
 		lpi2c_imx_read_rxfifo(lpi2c_imx);
-
-	if (temp & MSR_TDF)
+	else if (temp & MSR_TDF)
 		lpi2c_imx_write_txfifo(lpi2c_imx);
 
-	if (temp & MSR_NDF)
-		complete(&lpi2c_imx->complete);
-
+ret:
 	return IRQ_HANDLED;
 }
 
-- 
2.34.1