> Subject: Re: [PATCH] drm/i915/backlight: Remove try_vesa_interface > > On Tue, Feb 24, 2026 at 08:43:22AM +0530, Suraj Kandpal wrote: > > Remove try_vesa_interface. This is because we now make VESA Interface > > as a fallback mechanism for Panels which needs VESA DPCD AUX backlight > > mechanism to work but have a broken VBT indicating otherwise. > > While at in sneak in a small comment cleanup too. > > This broke the backlight on my VLV chromebook. > > i915 0000:00:02.0: [drm:intel_dp_aux_init_backlight_funcs [i915]] > [CONNECTOR:98:eDP-1] Detected unsupported HDR backlight interface version > 0 > +i915 0000:00:02.0: [drm:intel_dp_aux_init_backlight_funcs [i915]] > [CONNECTOR:98:eDP-1] AUX Backlight Control Supported! > +i915 0000:00:02.0: [drm:intel_dp_aux_init_backlight_funcs [i915]] > +[CONNECTOR:98:eDP-1] Using VESA eDP backlight controls > i915 0000:00:02.0: [drm:intel_panel_init [i915]] [CONNECTOR:98:eDP-1] DRRS > type: none > +i915 0000:00:02.0: [drm:drm_edp_backlight_init [drm_display_helper]] > +AUX C/DP C: Found backlight: aux_set=1 aux_enable=0 mode=1 > +i915 0000:00:02.0: [drm:drm_edp_backlight_init [drm_display_helper]] > +AUX C/DP C: Backlight caps: level=1023/1023 pwm_freq_pre_divider=0 > +lsb_reg_used=1 > +i915 0000:00:02.0: [drm:intel_dp_aux_vesa_setup_backlight [i915]] > +[CONNECTOR:98:eDP-1] AUX VESA backlight enable is controlled through > +PWM > +i915 0000:00:02.0: [drm:intel_dp_aux_vesa_setup_backlight [i915]] > +[CONNECTOR:98:eDP-1] AUX VESA backlight level is controlled through > +DPCD > i915 0000:00:02.0: [drm:vlv_setup_backlight [i915]] [CONNECTOR:98:eDP-1] > Using native PWM for backlight control (on pipe A) > -i915 0000:00:02.0: [drm:intel_backlight_setup [i915]] [CONNECTOR:98:eDP-1] > backlight initialized, enabled, brightness 7812/7812 > +i915 0000:00:02.0: [drm:intel_dp_aux_vesa_setup_backlight [i915]] > +[CONNECTOR:98:eDP-1] Using AUX VESA interface for backlight control > +i915 0000:00:02.0: [drm:intel_backlight_setup [i915]] > +[CONNECTOR:98:eDP-1] backlight initialized, disabled, brightness > +1023/1023
Hi Ville can you provide the full logs from boot with debug set to 0x10e and also when you manipulate your backlight I did have a commit that checks if vesa is actually possible because some panels report vesa support even though they really cannot 0fb03890d182 drm/i915/backlight: Check if VESA backlight is possible Also what would be the edp Panel model I can try replicate this issue locally after I find a vlv machine Regards, Suraj Kandpal > > > > > Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/15679 > > Signed-off-by: Suraj Kandpal <[email protected]> > > --- > > .../drm/i915/display/intel_dp_aux_backlight.c | 19 > > +++++++------------ > > 1 file changed, 7 insertions(+), 12 deletions(-) > > > > diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c > > b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c > > index eb05ef4bd9f6..a8e9872566cd 100644 > > --- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c > > +++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c > > @@ -644,9 +644,10 @@ int intel_dp_aux_init_backlight_funcs(struct > intel_connector *connector) > > struct intel_dp *intel_dp = intel_attached_dp(connector); > > struct drm_device *dev = connector->base.dev; > > struct intel_panel *panel = &connector->panel; > > - bool try_intel_interface = false, try_vesa_interface = false; > > + bool try_intel_interface = false; > > > > - /* Check the VBT and user's module parameters to figure out which > > + /* > > + * Check the VBT and user's module parameters to figure out which > > * interfaces to probe > > */ > > switch (display->params.enable_dpcd_backlight) { @@ -655,7 +656,6 > @@ > > int intel_dp_aux_init_backlight_funcs(struct intel_connector *connector) > > case INTEL_DP_AUX_BACKLIGHT_AUTO: > > switch (panel->vbt.backlight.type) { > > case INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE: > > - try_vesa_interface = true; > > break; > > case INTEL_BACKLIGHT_DISPLAY_DDI: > > try_intel_interface = true; > > @@ -668,20 +668,12 @@ int intel_dp_aux_init_backlight_funcs(struct > intel_connector *connector) > > if (panel->vbt.backlight.type != > INTEL_BACKLIGHT_VESA_EDP_AUX_INTERFACE) > > try_intel_interface = true; > > > > - try_vesa_interface = true; > > - break; > > - case INTEL_DP_AUX_BACKLIGHT_FORCE_VESA: > > - try_vesa_interface = true; > > break; > > case INTEL_DP_AUX_BACKLIGHT_FORCE_INTEL: > > try_intel_interface = true; > > break; > > } > > > > - /* For eDP 1.5 and above we are supposed to use VESA interface for > brightness control */ > > - if (intel_dp->edp_dpcd[0] >= DP_EDP_15) > > - try_vesa_interface = true; > > - > > /* > > * Since Intel has their own backlight control interface, the majority > > of > machines out there > > * using DPCD backlight controls with Intel GPUs will be using this > > interface as opposed to @@ -694,6 +686,9 @@ int > intel_dp_aux_init_backlight_funcs(struct intel_connector *connector) > > * panel with Intel's OUI - which is also required for us to be able to > detect Intel's > > * backlight interface at all. This means that the only sensible way > > for us > to detect both > > * interfaces is to probe for Intel's first, and VESA's second. > > + * > > + * Also there is a chance some VBT's may advertise false Intel backlight > support even if the > > + * tcon's DPCD says otherwise. This mean we keep VESA interface as > fallback in that case. > > */ > > if (try_intel_interface && > intel_dp_aux_supports_hdr_backlight(connector) && > > intel_dp->edp_dpcd[0] <= DP_EDP_14b) { @@ -703,7 +698,7 @@ int > > intel_dp_aux_init_backlight_funcs(struct intel_connector *connector) > > return 0; > > } > > > > - if (try_vesa_interface && > intel_dp_aux_supports_vesa_backlight(connector)) { > > + if (intel_dp_aux_supports_vesa_backlight(connector)) { > > drm_dbg_kms(dev, "[CONNECTOR:%d:%s] Using VESA eDP > backlight controls\n", > > connector->base.base.id, connector->base.name); > > panel->backlight.funcs = &intel_dp_vesa_bl_funcs; > > -- > > 2.34.1 > > -- > Ville Syrjälä > Intel
