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 2/2] gpio: pcf857x: add support for reset-gpios on (most) PCA967x
Date: Thu, 20 Feb 2025 22:52:32 +0100 [thread overview]
Message-ID: <2590885.4XsnlVU6TS@diego> (raw)
In-Reply-To: <20250220-pca976x-reset-driver-v1-2-6abbf043050e@cherry.de>
Am Donnerstag, 20. Februar 2025, 10:56:52 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.
> Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
With the gpio-consumer fixed, reset-gpio handling works nicely
on my rk3588-tiger-haikou with the DSI display overlay, so
Tested-by: Heiko Stuebner <heiko@sntech.de>
prev parent reply other threads:[~2025-02-20 21:52 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-20 9:56 [PATCH 0/2] gpio: pcf857x: add support for reset-gpios on (most) PCA967x Quentin Schulz
2025-02-20 9:56 ` [PATCH 1/2] dt-bindings: gpio: nxp,pcf8575: add reset GPIO Quentin Schulz
2025-02-20 12:24 ` Laurent Pinchart
2025-02-20 13:11 ` Quentin Schulz
2025-02-20 21:51 ` Heiko Stübner
2025-02-20 9:56 ` [PATCH 2/2] gpio: pcf857x: add support for reset-gpios on (most) PCA967x Quentin Schulz
2025-02-20 10:52 ` Heiko Stübner
2025-02-20 12:13 ` Quentin Schulz
2025-02-20 12:28 ` Laurent Pinchart
2025-02-20 13:20 ` Bartosz Golaszewski
2025-02-20 21:52 ` Heiko Stübner [this message]
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