Re: [PATCH 1/3] phy: phy-can-transceiver: default silent GPIO to high during probe

From: Frank Li <Frank.li@oss.nxp.com>
To: haibo.chen@oss.nxp.com
Cc: Marc Kleine-Budde <mkl@pengutronix.de>,
	Vincent Mailhol <mailhol@kernel.org>,
	Vinod Koul <vkoul@kernel.org>,
	Neil Armstrong <neil.armstrong@linaro.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>, Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Conor Dooley <conor+dt@kernel.org>, Frank Li <Frank.Li@nxp.com>,
	Sascha Hauer <s.hauer@pengutronix.de>,
	Pengutronix Kernel Team <kernel@pengutronix.de>,
	Fabio Estevam <festevam@gmail.com>,
	linux-can@vger.kernel.org, linux-phy@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org,
	imx@lists.linux.dev, Haibo Chen <haibo.chen@nxp.com>,
	qijian.guo@nxp.com
Subject: Re: [PATCH 1/3] phy: phy-can-transceiver: default silent GPIO to high during probe
Date: Thu, 30 Jul 2026 09:47:51 -0500	[thread overview]
Message-ID: <amtkF1NXKN_nR2vE@SMW015318> (raw)
In-Reply-To: <20260730-can-share-silent-v1-1-63fd603f943d@nxp.com>

On Thu, Jul 30, 2026 at 12:33:26PM +0800, haibo.chen@oss.nxp.com wrote:
> From: Haibo Chen <haibo.chen@nxp.com>
>
> The silent pin of the CAN transceiver is active high, asserting it puts
> the transceiver into silent (listen-only) mode where the transmitter is
> disabled.
>
> At probe time, and before the PHY is powered on, the transceiver should
> default to silent mode. This is the correct and lower-power state: the
> transceiver should not actively drive the CAN bus until the PHY is
> explicitly powered on. Requesting the silent GPIO as GPIOD_OUT_LOW leaves
> the transceiver in normal mode by default, which is both incorrect and
> wastes power.
>
> Request the silent GPIO as GPIOD_OUT_HIGH so the transceiver starts in
> silent mode, and let the power_on/power_off callbacks manage the mode
> afterwards.
>
> Signed-off-by: Haibo Chen <haibo.chen@nxp.com>
> ---

Reviewed-by: Frank Li <Frank.Li@nxp.com>

>  drivers/phy/phy-can-transceiver.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/phy/phy-can-transceiver.c b/drivers/phy/phy-can-transceiver.c
> index 75dc49e75ca0e0e90a1b1b140dcaf8033ec02c50..9aa30662105f063fb6d0e60fd04a95c8d635a515 100644
> --- a/drivers/phy/phy-can-transceiver.c
> +++ b/drivers/phy/phy-can-transceiver.c
> @@ -198,7 +198,7 @@ static int can_transceiver_phy_probe(struct platform_device *pdev)
>
>  		if (drvdata->flags & CAN_TRANSCEIVER_SILENT_PRESENT) {
>  			silent_gpio = devm_gpiod_get_index_optional(dev, "silent", i,
> -								    GPIOD_OUT_LOW);
> +								    GPIOD_OUT_HIGH);
>  			if (IS_ERR(silent_gpio))
>  				return PTR_ERR(silent_gpio);
>  			can_transceiver_phy->silent_gpio = silent_gpio;
>
> --
> 2.34.1
>
>

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