On 2026-07-30 13:17, Fangzhi Zuo wrote:
> why:
> HDMI 2.1 Auto Low-Latency Mode (ALLM) lets a Source request the Sink's
> low-latency mode through the HF-VSIF. amdgpu never set ALLM_Mode in the
> HF-VSIF, so ALLM was never signalled to the sink.
>
> how:
> - Add an allm capability flag to struct dc_edid_caps and populate it in
> dm_helpers_parse_edid_caps() from the HF-VSDB ALLM bit parsed by DRM
> core (connector->display_info.hdmi.allm).
> - In create_stream_for_sink(), build the HF-VSIF with ALLM_Mode set when
> the sink advertises ALLM and the content type is Game (content-type =
> Game is how userspace requests low-latency mode, HDMI GCTS HF1-56).
> - In update_freesync_state_on_stream(), also set ALLM_Mode when
> Gaming-VRR is active (VRR_EN=1, HDMI GCTS HF1-58 step 8.3.1), and push
> the updated HF-VSIF (vsp_infopacket) as a stream update.
>
> Signed-off-by: Fangzhi Zuo <[email protected]>
> ---
> .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 35 ++++++++++++++++++-
> .../display/amdgpu_dm/amdgpu_dm_connector.c | 18 ++++++++--
> .../amd/display/amdgpu_dm/amdgpu_dm_helpers.c | 5 ++-
> drivers/gpu/drm/amd/display/dc/dc_types.h | 3 ++
> 4 files changed, 57 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index 223b562f7005..fc3005ecc681 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -3895,6 +3895,36 @@ static void update_freesync_state_on_stream(
> new_stream->vrr_infopacket = vrr_infopacket;
> new_stream->allow_freesync =
> mod_freesync_get_freesync_enabled(&vrr_params);
>
> + /*
> + * HDMI ALLM: transmit the HF-VSIF with ALLM_Mode=1 when the sink
> + * advertises ALLM in the SCDS and either the content type is Game
> + * (HF1-56) or Gaming-VRR is active (VRR_EN=1, HF1-58 step 8.3.1).
> + * HDMI 2.1 7.6.6.
> + */
> + if (new_stream->signal == SIGNAL_TYPE_HDMI_TYPE_A ||
> + new_stream->signal == SIGNAL_TYPE_HDMI_FRL) {
> + struct dc_info_packet vsp_infopacket = {0};
> + bool allm = new_stream->sink->edid_caps.allm &&
We have an `aconn` in this function above, so we can simply get the allm
bit from the connector:
bool sink_allm = aconn && aconn->base.display_info.hdmi.allm;
bool allm = sink_allm &&
(new_stream->content_type == DISPLAY_CONTENT_TYPE_GAME
||
vrr_params.state == VRR_STATE_ACTIVE_VARIABLE ||
vrr_params.state == VRR_STATE_ACTIVE_FIXED);
Then we don't need to add a new allm bool to edid_caps.
Harry
> + (new_stream->content_type == DISPLAY_CONTENT_TYPE_GAME
> ||
> + vrr_params.state == VRR_STATE_ACTIVE_VARIABLE ||
> + vrr_params.state == VRR_STATE_ACTIVE_FIXED);
> + bool allm_changed;
> +
> + mod_build_hf_vsif_infopacket(new_stream, &vsp_infopacket, allm,
> allm);
> +
> + allm_changed = memcmp(&new_stream->vsp_infopacket,
> &vsp_infopacket,
> + sizeof(vsp_infopacket)) != 0;
> + new_crtc_state->freesync_vrr_info_changed |= allm_changed;
> + new_stream->vsp_infopacket = vsp_infopacket;
> +
> + if (allm_changed)
> + drm_dbg_driver(adev_to_drm(adev),
> + "ALLM: flip on crtc=%u: sink_allm=%d
> content_type=%d vrr_state=%d -> ALLM_Mode=%d\n",
> + new_crtc_state->base.crtc->base.id,
> + new_stream->sink->edid_caps.allm,
> + new_stream->content_type, vrr_params.state,
> allm);
> + }
> +
> if (new_crtc_state->freesync_vrr_info_changed)
> drm_dbg_kms(adev_to_drm(adev), "VRR packet update: crtc=%u
> enabled=%d state=%d",
> new_crtc_state->base.crtc->base.id,
> @@ -4429,9 +4459,12 @@ static void amdgpu_dm_commit_planes(struct
> drm_atomic_state *state,
> }
>
> if (acrtc_state->stream) {
> - if (acrtc_state->freesync_vrr_info_changed)
> + if (acrtc_state->freesync_vrr_info_changed) {
> bundle->stream_update.vrr_infopacket =
> &acrtc_state->stream->vrr_infopacket;
> + bundle->stream_update.vsp_infopacket =
> + &acrtc_state->stream->vsp_infopacket;
> + }
> }
> }
>
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_connector.c
> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_connector.c
> index ebead39939a6..430f1628ced0 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_connector.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_connector.c
> @@ -1511,8 +1511,22 @@ create_stream_for_sink(struct drm_connector *connector,
> update_stream_signal(stream, sink);
>
> if (stream->signal == SIGNAL_TYPE_HDMI_TYPE_A ||
> - stream->signal == SIGNAL_TYPE_HDMI_FRL)
> - mod_build_hf_vsif_infopacket(stream, &stream->vsp_infopacket,
> false, false);
> + stream->signal == SIGNAL_TYPE_HDMI_FRL) {
> + /*
> + * Enable HDMI ALLM (Auto Low-Latency Mode) when the sink
> + * advertises ALLM in the SCDS and the content type is Game.
> + * Setting content-type = Game is how userspace requests the
> + * Sink's low-latency mode (HDMI GCTS HF1-56).
> + */
> + bool allm = sink->edid_caps.allm &&
> + stream->content_type == DISPLAY_CONTENT_TYPE_GAME;
> +
> + drm_dbg_driver(dev,
> + "ALLM: set mode: sink_allm=%d content_type=%d ->
> ALLM_Mode=%d\n",
> + sink->edid_caps.allm, stream->content_type, allm);
> +
> + mod_build_hf_vsif_infopacket(stream, &stream->vsp_infopacket,
> allm, allm);
> + }
>
> if (stream->signal == SIGNAL_TYPE_DISPLAY_PORT ||
> stream->signal == SIGNAL_TYPE_DISPLAY_PORT_MST ||
> 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 42f5673acb4d..e69ce0a1b4b4 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
> @@ -197,7 +197,10 @@ enum dc_edid_status dm_helpers_parse_edid_caps(
> edid_caps->display_name,
> AUDIO_INFO_DISPLAY_NAME_SIZE_IN_CHARS);
>
> - edid_caps->edid_hdmi = connector->display_info.is_hdmi;
> + if (connector->display_info.is_hdmi) {
> + edid_caps->edid_hdmi = true;
> + edid_caps->allm = connector->display_info.hdmi.allm;
> + }
>
> if (edid_caps->edid_hdmi) {
> populate_hdmi_info_from_connector(link->dc->config.enable_frl,
> &connector->display_info.hdmi, edid_caps);
> diff --git a/drivers/gpu/drm/amd/display/dc/dc_types.h
> b/drivers/gpu/drm/amd/display/dc/dc_types.h
> index 3edeb94fba23..ae409cc59ae4 100644
> --- a/drivers/gpu/drm/amd/display/dc/dc_types.h
> +++ b/drivers/gpu/drm/amd/display/dc/dc_types.h
> @@ -226,6 +226,9 @@ struct dc_edid_caps {
> /*HDMI 2.0 caps*/
> bool lte_340mcsc_scramble;
>
> + /* HDMI 2.1 caps */
> + bool allm;
> +
> bool edid_hdmi;
> bool hdr_supported;
> bool rr_capable;
