From: "Heiko Stübner" <heiko@sntech.de>
To: Linus Walleij <linus.walleij@linaro.org>,
Bartosz Golaszewski <brgl@bgdev.pl>,
Rob Herring <robh@kernel.org>,
Krzysztof Kozlowski <krzk+dt@kernel.org>,
Conor Dooley <conor+dt@kernel.org>,
Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>,
Quentin Schulz <foss+kernel@0leil.net>
Cc: linux-gpio@vger.kernel.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org,
Quentin Schulz <quentin.schulz@cherry.de>
Subject: Re: [PATCH v2 2/2] gpio: pcf857x: add support for reset-gpios on (most) PCA967x
Date: Fri, 21 Feb 2025 14:48:55 +0100 [thread overview]
Message-ID: <1947442.eGJsNajkDb@diego> (raw)
In-Reply-To: <20250221-pca976x-reset-driver-v2-2-a2bcb9fdc256@cherry.de>
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>
prev parent reply other threads:[~2025-02-21 13:49 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-21 10:14 [PATCH v2 0/2] gpio: pcf857x: add support for reset-gpios on (most) PCA967x Quentin Schulz
2025-02-21 10:14 ` [PATCH v2 1/2] dt-bindings: gpio: nxp,pcf8575: add reset GPIO Quentin Schulz
2025-02-21 16:49 ` Laurent Pinchart
2025-02-21 16:52 ` Conor Dooley
2025-02-21 10:14 ` [PATCH v2 2/2] gpio: pcf857x: add support for reset-gpios on (most) PCA967x Quentin Schulz
2025-02-21 13:48 ` Heiko Stübner [this message]
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