Re: [PATCH v2 2/2] gpio: pcf857x: add support for reset-gpios on (most) PCA967x

Heiko Stübner
2025-02-21T13:49:01Z

Am Freitag, 21. Februar 2025, 11:14:27 MEZ schrieb Quentin Schulz:
> From: Quentin Schulz <quentin.schulz@cherry.de>
>
> The PCA9670, PCA9671, PCA9672 and PCA9673 all have a RESETN input pin
> that is used to reset the I2C GPIO expander.
>
> One needs to hold this pin low for at least 4us and the reset should be
> finished after about 100us according to the datasheet[1]. Once the reset
> is done, the "registers and I2C-bus state machine will be held in their
> default state until the RESET input is once again HIGH.".
>
> Because the logic is reset, the latch values eventually provided in the
> Device Tree via lines-initial-states property are inapplicable so they
> are simply ignored if a reset GPIO is provided.
>
> [1] https://www.nxp.com/docs/en/data-sheet/PCA9670.pdf 8.5 and fig 22.
>
> Tested-by: Heiko Stuebner <heiko@sntech.de> # RK3588 Tiger Haikou Video Demo
> Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>

Reviewed-by: Heiko Stuebner <heiko@sntech.de>