linux-kernel - Re: [PATCH v1 2/2] arm64: dts: qcom: qcs6490-rb3gen2: Enable CAN bus controller

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Message-ID: <wbx2qrkhpsntggzqkzkpi4sa6qv3buhkjbwmjoa7zgw2oc4b7u@qugyhcxb6qrh>
Date: Fri, 9 Jan 2026 16:05:50 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Viken Dadhaniya <viken.dadhaniya@....qualcomm.com>
Cc: mkl@...gutronix.de, mani@...nel.org, thomas.kopp@...rochip.com,
        mailhol@...nel.org, robh@...nel.org, krzk+dt@...nel.org,
        conor+dt@...nel.org, andersson@...nel.org, konradybcio@...nel.org,
        linux-can@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        mukesh.savaliya@....qualcomm.com, anup.kulkarni@....qualcomm.com
Subject: Re: [PATCH v1 2/2] arm64: dts: qcom: qcs6490-rb3gen2: Enable CAN bus
 controller

On Fri, Jan 09, 2026 at 06:23:39PM +0530, Viken Dadhaniya wrote:
> 
> 
> On 1/8/2026 7:33 PM, Dmitry Baryshkov wrote:
> > On Thu, Jan 08, 2026 at 06:22:00PM +0530, Viken Dadhaniya wrote:
> >> Enable the MCP2518FD CAN controller on the QCS6490 RB3 Gen2 platform.
> >> The controller is connected via SPI3 and uses a 40 MHz oscillator.
> >> A GPIO hog for GPIO0 is included to configure the CAN transceiver in
> >> Normal mode during boot.
> > 
> > The main question is: what is so different between RB3 Gen2 and previous
> > RB boards which also incorporated this CAN controller? Are there any
> > board differences or is it that nobody tested the CAN beforehand?
> > 
> 
> The behavior is consistent across platforms, but I do not have details on
> how other platforms were tested.
> 
> On the RB3Gen2 board, communication with the PCAN interface requires the
> CAN transceiver to be in normal mode. Since the GPIO-controller support
> was recently integrated into the driver, I configured the transceiver using a
> GPIO hog property. Without this configuration, the transceiver is not set
> to normal mode, and CAN communication does not work.

How do we verify the mode on a running system? I have the boards, but I
don't have anything connected to them over the CAN bus.

BTW: can you recommend any simple setup to actually test the CAN bus on
those devices?

-- 
With best wishes
Dmitry