On 2018-05-01 13:42, Mike Looijmans wrote:
> 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.
I can't see any problems with this, and a reset at load time can certainly
be a benefit. Some questions below though...
Cheers,
Peter
> Signed-off-by: Mike Looijmans <mike.looijmans@xxxxxxxx>
> ---
> 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);
ndelay(4) ?
> + gpiod_set_value_cansleep(gpio, 0);
> + /* Datasheet specifies a 500 ns reset recovery time */
> + udelay(1);
ndelay(500) ?
> + }
>
> match = of_match_device(of_match_ptr(pca954x_of_match), &client->dev);
> if (match)
>
