AMD General > -----Original Message----- > From: amd-gfx <[email protected]> On Behalf Of > teapot > Sent: Wednesday, September 23, 2026 12:07 > To: Ata İlhan Köktürk <[email protected]>; amd- > [email protected] > Cc: Wentland, Harry <[email protected]>; Li, Sun peng (Leo) > <[email protected]>; Rodrigo Siqueira <[email protected]>; Deucher, > Alexander <[email protected]>; Koenig, Christian > <[email protected]>; David Airlie <[email protected]>; Simona > Vetter <[email protected]>; [email protected]; linux- > [email protected] > Subject: Re: [DRM] amdgpu: HDMI FreeSync not exposed on Samsung > S22C31x despite AMD VSDB > > [Some people who received this message don't often get email from > [email protected]. Learn why this is important at > https://aka.ms/LearnAboutSenderIdentification ] > > On 2026-09-22 20:27, Ata İlhan Köktürk wrote: > > Hi, > > > > I am investigating an issue where HDMI FreeSync is not exposed for a > > Samsung S22C31x monitor on an AMD Picasso/Raven 2 GPU, although the > > monitor advertises an AMD FreeSync range in its EDID and VRR works > > under Windows. > > > > Hardware/software: > > > > * GPU: 03:00.0 VGA compatible controller [0300]: > > Advanced Micro Devices, Inc. [AMD/ATI] Picasso/Raven 2 [Radeon Vega > > Series / Radeon Vega Mobile Series] [1002:15d8] (rev c2) > > * Kernel: 7.2.5-200.fc44 > > * Compositor: Sway (Wayland) > > * Monitor: Samsung S22C31x > > * Connector: HDMI-A-1 > > * EDID serial: H9DX100210 > > * Kernel command line includes: amdgpu.freesync_video=1 > > > > Observed: > > > > * swaymsg -t get_outputs reports "Adaptive sync: disabled" for HDMI-A-1. > > * Adaptive sync remains disabled at both 1920x1080@60 Hz and > 1920x1080@75 Hz. > > * The same monitor exposes and enables FreeSync under Windows. > > > > The EDID contains the following AMD Vendor-Specific Data Block: > > > > Vendor-Specific Data Block (AMD), OUI 00-00-1A: > > Version: 1 > > Feature Caps: 0x01 > > Minimum Refresh Rate: 48 Hz > > Maximum Refresh Rate: 75 Hz > > Flags 1.x: 0x00> > > The HDMI VSDB therefore appears to advertise a 48-75 Hz FreeSync range. > > > > There is also this message in dmesg: > > > > amdgpu 0000:03:00.0: [drm] Failed to setup vendor infoframe on > > connector HDMI-A-1: -22 > > > > I believe this is the -EINVAL path from > > drm_hdmi_vendor_infoframe_from_display_mode() for this timing and is > > probably unrelated to the FreeSync issue. > > > > The part I am currently investigating is > amdgpu_dm_update_freesync_caps(). > > > > For HDMI, the driver calls parse_hdmi_amd_vsdb(), which on this DCN > > configuration goes through the DMUB path: > > > > parse_hdmi_amd_vsdb() > > -> parse_edid_cea() > > -> parse_edid_cea_dmub() > > -> dm_edid_parser_send_cea() > > -> output->amd_vsdb.freesync_supported > > > > If the DMUB parser returns freesync_supported == 0, the driver does > > not expose the connector as VRR capable. > > > > What makes this interesting is that the DRM EDID parser also contains > > the corresponding AMD VSDB information in > > connector->display_info.amd_vsdb, while the DMUB result > > does not result in FreeSync being exposed. > > > > I am wondering about the following: > > > > 1. Is the AMD VSDB layout above expected to be accepted by the DMUB > > EDID parser, particularly with Feature Caps 0x01, Flags 1.x == 0x00, > > and no MCCS VCP code byte? > AFAIK the driver will consider HDMI FreeSync unavailable if MCCS VCP code is > 0x0. HDMI FreeSync needs this VCP code.> > > 2. If the DMUB parser rejects this form of AMD VSDB, should amdgpu_dm > > fall back to the software-parsed connector->display_info.amd_vsdb when > > determining FreeSync capability? > The amd_vsdb struct is currently only for the V2+ luminosity fields, and don't > affect FreeSync detection. I had added FreeSync fields support and those > changes are in drm-next, but haven't made it up to the Torvalds tree yet. > > > > I have a working kernel tree and can run diagnostic tests or test a > > small patch. I can also provide drm.debug output or DMUB-related > > traces if useful. > I think this might be a case where the Windows FreeSync detection has > diverged from the Linux detection, maybe Harry would be able to provide > more insight on this? > > The monitor's EDID would probably be useful too, I'm not quite sure how to > make sense of the edid-decode output since there's a few guessed fields in > the AMD VSDB block and hasn't been updated since 2024.> > > Thanks, > > Ata İlhan Köktürk > > Best, > Alex
Yes, we are working to switch parsing AMD VSDB from dmub to public drm. Will get it ready once internal validation is done.
