From: Mike Looijmans <mike.looijmans@topic.nl>
Date: Tue, 1 May 2018 13:42:12 +0200
Subject: i2c: mux: pca954x: force reset on probe if available

Git-commit: a2f8445d4ca2796283c07d4ba8e78718071de863
Patch-mainline: v4.18-rc1
References: fate#326530,fate#326531,fate#326535,fate#326538,fate#326539

Instead of just hogging the reset GPIO into deactivated state, activate and
then de-activate the reset. This allows for better recovery if the CPU was
reset halfway through an I2C transaction for example.

Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl>
Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@suse.com>
---
 drivers/i2c/muxes/i2c-mux-pca954x.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c
index 09bafd3e68fa..fe20b8ec5247 100644
--- a/drivers/i2c/muxes/i2c-mux-pca954x.c
+++ b/drivers/i2c/muxes/i2c-mux-pca954x.c
@@ -36,6 +36,7 @@
  */
 
 #include <linux/device.h>
+#include <linux/delay.h>
 #include <linux/gpio/consumer.h>
 #include <linux/i2c.h>
 #include <linux/i2c-mux.h>
@@ -389,10 +390,16 @@ static int pca954x_probe(struct i2c_client *client,
 	i2c_set_clientdata(client, muxc);
 	data->client = client;
 
-	/* Get the mux out of reset if a reset GPIO is specified. */
-	gpio = devm_gpiod_get_optional(&client->dev, "reset", GPIOD_OUT_LOW);
+	/* Reset the mux if a reset GPIO is specified. */
+	gpio = devm_gpiod_get_optional(&client->dev, "reset", GPIOD_OUT_HIGH);
 	if (IS_ERR(gpio))
 		return PTR_ERR(gpio);
+	if (gpio) {
+		udelay(1);
+		gpiod_set_value_cansleep(gpio, 0);
+		/* Give the chip some time to recover. */
+		udelay(1);
+	}
 
 	match = of_match_device(of_match_ptr(pca954x_of_match), &client->dev);
 	if (match)
-- 
2.11.0