Re: [PATCH v2 2/3] arm64: dts: qcom: Add HP EliteBook X G2q 14 AI

[Jason Pettit]

On Sun, 28 Jun 2026 16:02:24 +0300, Dmitry Baryshkov wrote:
> This is very surprising. Can you check, is it actually the DWC3 or is it
> some power supply that is being toggled by the USB controller? In the
> former case it would mean that we miss some bits of PHY programming and
> still depend on the USB host / USB part of the PHY.

I tried to check this. I am fairly new to this, so I mostly poked at it on
the hardware. Here is what I did and what I saw, and you can probably read
more into it than I can.

1. First, with &usb_2 (the dwc3, HS-only) and &usb_2_hsphy enabled, HDMI
   works. I looked at the power state on that boot to see if the dwc3 turns
   on anything the DP side might also need. As far as I can tell they are
   separate. The combo PHY, the dwc3, and the DP controller are each in a
   different power domain, and the PHY's regulators show up under the PHY,
   not the dwc3:

     gcc_usb_2_phy_gdsc    on
         88e1000.phy                       active   (the combo PHY)
     gcc_usb30_tert_gdsc   on
         a000000.usb                       active   (the dwc3)
     mmcx                  on
         af64000.displayport-controller    active   (mdss_dp2)

     vreg_l2f_e0_0p94 -> 88e1000.phy-refgen
     vreg_l3f_e0_0p91 -> 88e1000.phy-vdda-pll
     vreg_l4h_e0_1p2  -> 88e1000.phy-vdda-phy

   So I did not find a rail or GDSC that the dwc3 owns and the PHY needs.

2. Then I removed &usb_2 and &usb_2_hsphy, rebuilt, and rebooted. mdss_dp2
   still binds:

     msm_dpu ae01000.display-controller: bound af64000.displayport-controller

   and HDMI-A-1 still reads connected, so the PHY seems powered and the AUX
   side is working, but there is no picture on the monitor.

3. Putting the two nodes back makes the picture come back, and the PHY's
   supplies look the same either way.

So from what I can see the power is not the thing being toggled. The PHY
stays powered without the dwc3, but DP still has no image. That seems to
line up with your first option, that something on the USB side of the PHY
still has to be brought up.

For now I have kept the dwc3 enabled as a workaround. If this is a driver
issue and someone has a fix or a pointer, I am happy to test it on the
hardware.

Thanks,
Jason