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

Konrad Dybcio
2026-04-22T13:04:58Z

On 4/22/26 2:31 PM, Mahadevan P wrote:
>
>
> On 4/22/2026 4:19 PM, Konrad Dybcio wrote:
>> 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?
>>
>
> yes

Thanks for confirming!

Konrad