Re: [PATCH RFC 06/25] drm/connector: hdmi: Add VTEM EMP generation
From: Vidith Madhu <hidden>
Date: 2026-09-25 03:49:08
Also in:
dri-devel, linux-arm-kernel, linux-rockchip, lkml
On Mon, 21 Sep 2026, Nicolas Frattaroli wrote:
quoted hunk ↗ jump to hunk
From: Derek Foreman <redacted> Add VTEM EMP generation to enable variable refresh rate signalling over HDMI. These infoframes are only generated if the sink supports VRR. Signed-off-by: Derek Foreman <redacted> Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com> --- drivers/gpu/drm/display/drm_hdmi_state_helper.c | 60 +++++++++++++++++++++++++ include/drm/drm_connector.h | 5 +++ 2 files changed, 65 insertions(+)diff --git a/drivers/gpu/drm/display/drm_hdmi_state_helper.c b/drivers/gpu/drm/display/drm_hdmi_state_helper.c index d55548399687..33d0c9491643 100644 --- a/drivers/gpu/drm/display/drm_hdmi_state_helper.c +++ b/drivers/gpu/drm/display/drm_hdmi_state_helper.c@@ -853,6 +853,56 @@ static int hdmi_generate_hdmi_vendor_infoframe(const struct drm_connector *conne return 0; } +static int hdmi_generate_emp_infoframe_vtem(const struct drm_connector *connector, + struct drm_connector_state *conn_state) +{ + const struct drm_display_info *info = &connector->display_info; + const struct drm_crtc_state *crtc_state = + drm_atomic_get_crtc_state(conn_state->state, conn_state->crtc); + struct drm_connector_hdmi_infoframe *infoframe = + &conn_state->hdmi.infoframes.vtem; + struct hdmi_emp_infoframe_vtem *vtem = + &infoframe->data.vtem; + const struct drm_crtc_vrr_state *vrr = &crtc_state->vrr_state; + int vfront; + + infoframe->set = false; + + if (!connector->hdmi.funcs->vtem.write_infoframe) + return 0; + + if (!info->hdmi.vrr_capable) + return 0; + + hdmi_emp_infoframe_vtem_init(vtem); + if (!crtc_state->vrr_enabled || vrr->vic) { + vtem->base_refresh_rate = 0; + vtem->base_vfront = 0;
It shouldn't hurt to always populate base_refresh_rate and base_vfront, might be cleaner to skip this check.
+ } else {
+ vtem->base_refresh_rate = drm_mode_vrefresh(&crtc_state->mode);
+ vfront = crtc_state->adjusted_mode.crtc_vsync_start -
+ crtc_state->adjusted_mode.crtc_vdisplay;
+ if (vfront > U8_MAX || vfront < 0)
+ return -EINVAL;
+
+ vtem->base_vfront = vfront;
+ }
+ vtem->fva_factor_m1 = 0;
+ infoframe->set = true;
+
+ if (!crtc_state->vrr_enabled) {I don't think we should use the vrr_enabled CRTC property to determine
VRR_EN in the VTEM EMP. Transitioning the VRR mode sink-side typically causes
blanking, and it was discussed in patch [03/25] that drivers should be
free to handle vrr_enabled changes as a seamless switch since it only
concerns source-side VRR state (this is how the NVIDIA driver handles it).
Maybe it would make sense to extend the qms_enabled connector property
introduced in this patchset to an enum of {Off, Gaming, QMS}? This would allow
a standard path to control the VRR state on the sink, separately from
vrr_enabled. quoted hunk ↗ jump to hunk
+ vtem->m_const = false; + vtem->game_vrr_en = false; + return 0; + } + + vtem->game_vrr_en = true; + + vtem->m_const = !vrr->dynamic; + + return 0; +} + static int hdmi_generate_infoframes(const struct drm_connector *connector, struct drm_connector_state *conn_state)@@ -884,6 +934,10 @@ hdmi_generate_infoframes(const struct drm_connector *connector, if (ret) return ret; + ret = hdmi_generate_emp_infoframe_vtem(connector, conn_state); + if (ret) + return ret; + return 0; }@@ -1494,6 +1548,12 @@ int drm_atomic_helper_connector_hdmi_update_infoframes(struct drm_connector *con goto out; } + if (info->hdmi.vrr_capable) + ret = write_or_clear_infoframe(connector, + &funcs->vtem, "VTEM", + &old_conn_state->hdmi.infoframes.vtem, + &new_conn_state->hdmi.infoframes.vtem); + out: mutex_unlock(&connector->hdmi.infoframes.lock); return ret;diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h index e561a444515f..6e431eb81705 100644 --- a/include/drm/drm_connector.h +++ b/include/drm/drm_connector.h@@ -1180,6 +1180,11 @@ struct drm_connector_hdmi_state { * matching our state. */ struct drm_connector_hdmi_infoframe hdmi; + + /** + * @vtem: VTEM EMP infoframes structure matching our state. + */ + struct drm_connector_hdmi_infoframe vtem; } infoframes; /**-- 2.55.0