Re: [PATCH] arm64: dts: qcom: qcs6490-rb3gen2: Enable 4-lane DisplayPort Alt Mode

Konrad Dybcio
2026-04-22T10:49:36Z

On 4/20/26 12:00 PM, Mahadevan P wrote:
> Add the mode-switch property to the QMP combo PHY so that mode-switch
> events are routed to it, allowing the PHY to enter DisplayPort Alternate
> Mode. Expand the DP data-lanes assignment from two to four lanes to make
> use of the full link bandwidth available in this configuration.
>
> Signed-off-by: Mahadevan P <mahadevan.p@oss.qualcomm.com>
> ---
> arch/arm64/boot/dts/qcom/qcs6490-rb3gen2.dts | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/boot/dts/qcom/qcs6490-rb3gen2.dts b/arch/arm64/boot/dts/qcom/qcs6490-rb3gen2.dts
> index e393ccf1884a..0c180e49816f 100644
> --- a/arch/arm64/boot/dts/qcom/qcs6490-rb3gen2.dts
> +++ b/arch/arm64/boot/dts/qcom/qcs6490-rb3gen2.dts
> @@ -789,7 +789,7 @@ &mdss_dp {
> };
>
> &mdss_dp_out {
> - data-lanes = <0 1>;
> + data-lanes = <0 1 2 3>;
> remote-endpoint = <&usb_dp_qmpphy_dp_in>;

There was an issue with this on a similar kodiak-iot board:

https://lore.kernel.org/linux-arm-msm/zjmf27y5i6ypba3nvsxxceuxn6yogp46lmtrjua37qa4ibrleq@4qv5s2wirgdh/

Have you confirmed (through debugfs) that 4 lanes are in use when
running this on r3g2?

> };
>
> @@ -1391,6 +1391,7 @@ &usb_1_qmpphy {
> vdda-phy-supply = <&vreg_l6b_1p2>;
> vdda-pll-supply = <&vreg_l1b_0p912>;
>
> + mode-switch;

This should be moved to kodiak.dtsi

Konrad