i2c: imx: when being a target, mark the last read as processed

[ Upstream commit 87aec499368d488c20292952d6d4be7cb9e49c5e ]

When being a target, NAK from the controller means that all bytes have
been transferred. So, the last byte needs also to be marked as
'processed'. Otherwise index registers of backends may not increase.

Fixes: f7414cd692 ("i2c: imx: support slave mode for imx I2C driver")
Signed-off-by: Corey Minyard <minyard@acm.org>
Tested-by: Andrew Manley <andrew.manley@sealingtech.com>
Reviewed-by: Andrew Manley <andrew.manley@sealingtech.com>
Reviewed-by: Oleksij Rempel <o.rempel@pengutronix.de>
[wsa: fixed comment and commit message to properly describe the case]
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/i2c/busses/i2c-imx.c

@@ -771,6 +771,11 @@ static irqreturn_t i2c_imx_slave_handle(struct imx_i2c_struct *i2c_imx,
 		ctl &= ~I2CR_MTX;
 		imx_i2c_write_reg(ctl, i2c_imx, IMX_I2C_I2CR);
 		imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR);
+
+		/* flag the last byte as processed */
+		i2c_imx_slave_event(i2c_imx,
+				    I2C_SLAVE_READ_PROCESSED, &value);
+
 		i2c_imx_slave_finish_op(i2c_imx);
 		return IRQ_HANDLED;
 	}