On 2026-06-19 12:17, Deucher, Alexander wrote:
> Public
>
> Adding a few display folks to review.
>
> Thanks,
>
> Alex
>
>> -----Original Message-----
>> From: amd-gfx <[email protected]> On Behalf Of
>> Charles Munger
>> Sent: Friday, June 19, 2026 12:59 AM
>> To: [email protected]
>> Cc: Charles Munger <[email protected]>
>> Subject: [PATCH] drm/amdgpu: Add Paradetech OUI to VRR compat list
>>
>> There's at least two firmware versions on the CalDigit DP20-HDMI21 adapter,
>> which is powered by the ParadeTech PS196G chip. The first version has a bug
>> where it incorrectly neglects to set the DOWN_STREAM_PORT_PRESENT field
>> in the DPCD:
>>
>> $ sudo dpcd_reg read --offset=0x2205 --count=1 --device=0
>> 0x2205: 00
>> $ sudo dpcd_reg read --offset=0x0005 --count=1 --device=0
>> 0x0005: 00
>>
>> The newer one fixes this, and with this patch correctly negotiates VRR.
>>
>> [~]$ sudo dpcd_reg read --offset=0x5 --count=1 --device=2
>> 0x0005: 1d
>> [~]$ sudo dpcd_reg read --offset=0x2205 --count=1 --device=2
>> 0x2205: 1d
>>
>> So if you're using a Paradetech adapter and it doesn't negotiate VRR, check
>> that it has a firmware that produces the correct DPCD.
>>
>> Signed-off-by: Charles Munger <[email protected]>
>> ---
>> drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> diff --git
>> a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
>> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
>> index 6c827e6703a0..f463495d1c87 100644
>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_helpers.c
>> @@ -1410,6 +1410,7 @@ bool dm_helpers_is_vrr_pcon_allowed(const
Looks like this is based on the "drm/amd: VRR fixes, HDMI Gaming Features"
series, not directly on amd-staging-drm-next. I'll have to take another
closer look at that series.
Harry
>> struct dc_link *link, const struct drm
>> case DP_BRANCH_DEVICE_ID_00E04C:
>> case DP_BRANCH_DEVICE_ID_90CC24:
>> case DP_BRANCH_DEVICE_ID_2B02F0:
>> + case DP_BRANCH_DEVICE_ID_001CF8:
>> return true;
>> }
>>
>> --
>> 2.54.0
>
