> Subject: RE: [PATCH] drm/i915/backlight: Remove try_vesa_interface > > > Subject: RE: [PATCH] drm/i915/backlight: Remove try_vesa_interface > > > > > 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 > > Hi Ville, > Never mind I found the actual issue, slight oversight by me thanks for > bringing > this to my attention Went through the eDP spec again > > So apparently if we are only relying only on > BACKLIGHT_BRIGHTNESS_AUX_SET_CAPABLE > BACKLIGHT_AUX_ENABLE_CAPABLE should also be set. The only case where > one is independent of the other Is when we are using BL_ENABLE bit in which > case the brightness is a production function of the level and pwm level. > > Let me float a patch. > > Regards, > Suraj Kandpal >
I have sent the fix can you perhaps test it Regards, Suraj Kandpal > > > > 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
