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 > 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
