From: Mike Looijmans <mike.looijmans@topic.nl>
To: linux-i2c@vger.kernel.org
Cc: peda@axentia.se, linux-kernel@vger.kernel.org,
Mike Looijmans <mike.looijmans@topic.nl>
Subject: [PATCH] i2c-mux-pca954x: Force reset on probe if available
Date: Tue, 1 May 2018 13:42:12 +0200 [thread overview]
Message-ID: <1525174932-8865-1-git-send-email-mike.looijmans@topic.nl> (raw)
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>
---
drivers/i2c/muxes/i2c-mux-pca954x.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c
index 09bafd3..13e10d0 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 +390,17 @@ 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) {
+ /* Datasheet specifies a 4 ns reset-low time */
+ udelay(1);
+ gpiod_set_value_cansleep(gpio, 0);
+ /* Datasheet specifies a 500 ns reset recovery time */
+ udelay(1);
+ }
match = of_match_device(of_match_ptr(pca954x_of_match), &client->dev);
if (match)
--
1.9.1
next reply other threads:[~2018-05-01 11:42 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-01 11:42 Mike Looijmans [this message]
2018-05-08 6:36 ` [PATCH] i2c-mux-pca954x: Force reset on probe if available Peter Rosin
2018-05-08 8:06 ` Mike Looijmans
2018-05-08 8:06 ` Mike Looijmans
2018-05-19 21:58 ` Peter Rosin
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