Vega 56 failing to process EDID from VR Headset

[Paul Menzel]

Dear James,


Am 11.04.22 um 23:39 schrieb James Dutton:

> I have an Oculus Rift S, that I am trying to get working in Linux.

Please always mention the Linux kernel version.

> I have an AMD Vega 56  graphics card.
> 
> The VR headset plugs into a display port of the Vega56.
> The amdgpu driver sees the connection, and tries to process it.
> The problem is it cannot process the EDID, so fails to recognise the
> VR headset, and the VR headset does not work as a result.
> Please find the EDID below.
> I am guessing that the following is causing the problem:
> Established Timings I & II: none
> Standard Timings: none
> Forcing the driver to understand the Detailed mode, to which it is failing.
> If it helps, when attached to windows 10, it uses 1440x2560, portrait mode.
> Some dmesg lines that may be useful:
> // We should pick 1440x2560 as Windows picks that, but for some reason
> is rejects it with error 10.
> [10402.650734] [drm:create_validate_stream_for_sink [amdgpu]] Mode
> 1440x2560 (clk 571570) failed DC validation with error 10 (No DP link
> bandwidth)
> [10402.650991] [drm:update_stream_scaling_settings [amdgpu]]
> Destination Rectangle x:0  y:0  width:1440  height:2560
> [10402.651225] [drm:create_validate_stream_for_sink [amdgpu]] Mode
> 1440x2560 (clk 571570) failed DC validation with error 10 (No DP link
> bandwidth)

(Please use an email program, which does not wrap lines after 72 
characters.)

> Can anyone help give me with some pointers as to how to get the amdgpu
> driver to accept this EDID?

So, did you do any changes to Linux? Why do you think the EDID is at fault?

[…]

I suggest to analyze, why `No DP link bandwidth` is logged. The macro is 
`DC_NO_DP_LINK_BANDWIDTH`, and you should first check why 
`dp_validate_mode_timing()` in 
`drivers/gpu/drm/amd/display/dc/core/dc_link_dp.c` returns false.


Kind regards,

Paul


PS: Using the issue tracker [1] might make it easier to keep track of 
this problem, and also to attach all the necessary information.


[1]: https://gitlab.freedesktop.org/drm/amd/-/issues/