linux-kernel - Re: [PATCH] arm64: dts: imx91-11x11-frdm: fix CAN transceiver gpio

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Message-ID: <aWo3PZni1Pb9T6FI@bywater>
Date: Fri, 16 Jan 2026 14:03:57 +0100
From: Francesco Valla <francesco@...la.it>
To: Daniel Baluta <daniel.baluta@...il.com>
Cc: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>, devicetree@...r.kernel.org,
	imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: dts: imx91-11x11-frdm: fix CAN transceiver gpio

Hi Daniel,

On Fri, Jan 16, 2026 at 01:40:11PM +0200, Daniel Baluta wrote:
> On Thu, Jan 15, 2026 at 8:25 PM Francesco Valla <francesco@...la.it> wrote:
> >
> > According to the HW schematic, the CAN transceiver does not have an
> > enable pin but a silent one. Fix the GPIO property name and polarity.
> >
> > Fixes: b4bf5e55899e ("arm64: dts: freescale: Add FRDM-IMX91 basic support")
> 
> Just for clarification GPIO 23 is connected to a pin named CAN_STBY.
> So I wonder if it isn't
> better to use standby-gpios instead of silent-gpios?
> 
> I am looking at FRDM-IMX91 schematic file SPF-94610_A1.pdf.
> 
> But on the other hand we have
> 
> static const struct can_transceiver_data tja1051_drvdata = {
> »       .flags = CAN_TRANSCEIVER_SILENT_PRESENT | CAN_TRANSCEIVER_EN_PRESENT,
> };
> 
> So TJA1051 is not advertised as having a stdby flag.

Regardless of the name of the net, the functionality of a standby vs a
silent pin is very different. In this case, since the TJA1051 is
including a silent pin (pin S in he datasheet [0]), I think it's better
to declare it that way.

In case someone adds the support for a phy-oriented listen-only mode
(which is something I am thinking), this wouldn't break the integartion.

Regards,
Francesco

[0] https://www.nxp.com/docs/en/data-sheet/TJA1051.pdf