Quentin Schulz 087f8a6b8c gpio: pcf857x: add support for reset-gpios on (most) PCA967x ...

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
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
Link: https://lore.kernel.org/r/20250224-pca976x-reset-driver-v3-2-58370ef405be@cherry.de
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

2025-02-26 11:25:30 +01:00

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