[PATCH v3] i2c: imx-lpi2c: directly return ISR when detect a NACK

[carlos.song at nxp.com]

From: Carlos Song <carlos.song at nxp.com>

A NACK flag in ISR means i2c bus error. In such condition,
there is no need to do read/write operation.

In this patch, i2c will check MSR_NDF, MSR_RDF and MSR_TDF
flag in turn, it's making mutually exclusive NACK/read/write.
So when a NACK is received(MSR_NDF), i2c will return ISR
directly and then stop i2c transfer.

Fixes: a55fa9d0e42e ("i2c: imx-lpi2c: add low power i2c bus driver")
Signed-off-by: Carlos Song <carlos.song at nxp.com>
---
Changes for V3:
- modify commit log
- modify Signed-off-by list
---
 drivers/i2c/busses/i2c-imx-lpi2c.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c b/drivers/i2c/busses/i2c-imx-lpi2c.c
index c3287c887c6f..636ad3247982 100644
--- a/drivers/i2c/busses/i2c-imx-lpi2c.c
+++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
@@ -514,14 +514,12 @@ static irqreturn_t lpi2c_imx_isr(int irq, void *dev_id)
 	temp = readl(lpi2c_imx->base + LPI2C_MSR);
 	temp &= enabled;
 
-	if (temp & MSR_RDF)
-		lpi2c_imx_read_rxfifo(lpi2c_imx);
-
-	if (temp & MSR_TDF)
-		lpi2c_imx_write_txfifo(lpi2c_imx);
-
 	if (temp & MSR_NDF)
 		complete(&lpi2c_imx->complete);
+	else if (temp & MSR_RDF)
+		lpi2c_imx_read_rxfifo(lpi2c_imx);
+	else if (temp & MSR_TDF)
+		lpi2c_imx_write_txfifo(lpi2c_imx);
 
 	return IRQ_HANDLED;
 }
-- 
2.34.1