> -----Original Message----- > From: Intel-gfx <[email protected]> On Behalf Of Imre > Deak > Sent: Monday, 25 May 2026 15.55 > To: [email protected]; [email protected]; > [email protected] > Cc: Lyude Paul <[email protected]>; Lee, Shawn C <[email protected]> > Subject: [PATCH] drm/dp: Add DSC virtual DPCD quirk for Realtek MST branch > device > > The ASUS DC301 USB-C dock containing a Realtek MST branch device supports the > DSC decompression functionality on each of > the dock's downstream connectors, even though there is no discoverable > peer-to-peer virtual device in the MST topology (which > the DP Standard requires/suggests to control the DSC functionality on a > per-DFP basis). > Add the DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD quirk for this branch device > as well to enable the DSC decompression > functionality on all DFP connectors of the dock, similarly to how this is > done for dock's containing older Synaptics branch devices. > > Cc: Lyude Paul <[email protected]> > Reported-and-tested-by: Shawn C Lee <[email protected]>
Reviewed-by: Mika Kahola <[email protected]> > Signed-off-by: Imre Deak <[email protected]> > --- > drivers/gpu/drm/display/drm_dp_helper.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/gpu/drm/display/drm_dp_helper.c > b/drivers/gpu/drm/display/drm_dp_helper.c > index a6067471dd563..9c31e14cc413b 100644 > --- a/drivers/gpu/drm/display/drm_dp_helper.c > +++ b/drivers/gpu/drm/display/drm_dp_helper.c > @@ -2546,6 +2546,8 @@ static const struct dpcd_quirk dpcd_quirk_list[] = { > { OUI(0x00, 0x00, 0x00), DEVICE_ID('C', 'H', '7', '5', '1', '1'), > false, BIT(DP_DPCD_QUIRK_NO_SINK_COUNT) }, > /* Synaptics DP1.4 MST hubs can support DSC without virtual DPCD */ > { OUI(0x90, 0xCC, 0x24), DEVICE_ID_ANY, true, > BIT(DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD) }, > + /* Realtek DP1.4 MST hubs can support DSC without virtual DPCD */ > + { OUI(0x00, 0xe0, 0x4c), DEVICE_ID('D', 'p', '1', '.', '4', 0), true, > +BIT(DP_DPCD_QUIRK_DSC_WITHOUT_VIRTUAL_DPCD) }, > /* Synaptics DP1.4 MST hubs require DSC for some modes on which it > applies HBLANK expansion. */ > { OUI(0x90, 0xCC, 0x24), DEVICE_ID_ANY, true, > BIT(DP_DPCD_QUIRK_HBLANK_EXPANSION_REQUIRES_DSC) }, > /* MediaTek panels (at least in U3224KBA) require DSC for modes with a > short HBLANK on UHBR links. */ > -- > 2.49.1
