May be the older panel might not work well with this feature. David/Jani, what do you think about adding check that the panel is eDP 1.4 or later in the heuristic?
diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c index b25cd88fc1c5..e63f2296fd34 100644 --- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c +++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c @@ -292,7 +292,7 @@ intel_dp_aux_display_control_capable(struct intel_connector *connector) * via PWM pin or using AUX is better than using PWM pin. * * The heuristic to determine that using AUX pin is better than using PWM pin is - * that the panel support any of the feature list here. + * that the panel is eDP 1.4 or later and support any of the feature list here. * - Regional backlight brightness adjustment * - Backlight PWM frequency set * - More than 8 bits resolution of brightness level @@ -310,6 +310,10 @@ intel_dp_aux_display_control_heuristic(struct intel_connector *connector) if (!(intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_PWM_PIN_CAP)) return true; + /* Enable this for eDP 1.4 panel or later. */ + if (intel_dp->edp_dpcd[0] < DP_EDP_14) + return false; + /* Panel supports regional backlight brightness adjustment */ if (drm_dp_dpcd_readb(&intel_dp->aux, DP_EDP_GENERAL_CAP_3, ®_val) != 1) { On Mon, Jul 10, 2017 at 7:23 AM, David Weinehall <david.weineh...@linux.intel.com> wrote: > This reverts commit 560a758d39c616f83ac25ff6e0816a49ebe6401c. > > This patch has been identified to introduce a backlight regression > on at least two different platforms; either the heuristic is broken > (if so the patch needs to be reworked) or the in-kernel DPCD backlight > support is broken (if so it's premature to enable DPCD backlight > even if the platforms support it). > > Signed-off-by: David Weinehall <david.weineh...@linux.intel.com> > --- > drivers/gpu/drm/i915/i915_params.c | 7 ++- > drivers/gpu/drm/i915/i915_params.h | 1 - > drivers/gpu/drm/i915/intel_dp_aux_backlight.c | 61 > ++------------------------- > 3 files changed, 6 insertions(+), 63 deletions(-) > > diff --git a/drivers/gpu/drm/i915/i915_params.c > b/drivers/gpu/drm/i915/i915_params.c > index 88b9d3e6713a..bec5ade371b0 100644 > --- a/drivers/gpu/drm/i915/i915_params.c > +++ b/drivers/gpu/drm/i915/i915_params.c > @@ -63,7 +63,7 @@ struct i915_params i915 __read_mostly = { > .huc_firmware_path = NULL, > .enable_dp_mst = true, > .inject_load_failure = 0, > - .enable_dpcd_backlight = -1, > + .enable_dpcd_backlight = false, > .enable_gvt = false, > .enable_dbc = true, > }; > @@ -247,10 +247,9 @@ MODULE_PARM_DESC(enable_dp_mst, > module_param_named_unsafe(inject_load_failure, i915.inject_load_failure, > uint, 0400); > MODULE_PARM_DESC(inject_load_failure, > "Force an error after a number of failure check points (0:disabled > (default), N:force failure at the Nth failure check point)"); > -module_param_named_unsafe(enable_dpcd_backlight, i915.enable_dpcd_backlight, > int, 0600); > +module_param_named(enable_dpcd_backlight, i915.enable_dpcd_backlight, bool, > 0600); > MODULE_PARM_DESC(enable_dpcd_backlight, > - "Enable support for DPCD backlight control " > - "(-1:auto (default), 0:force disable, 1:force enabled if supported"); > + "Enable support for DPCD backlight control (default:false)"); > > module_param_named(enable_gvt, i915.enable_gvt, bool, 0400); > MODULE_PARM_DESC(enable_gvt, > diff --git a/drivers/gpu/drm/i915/i915_params.h > b/drivers/gpu/drm/i915/i915_params.h > index 057e203e6bda..6a88c76664db 100644 > --- a/drivers/gpu/drm/i915/i915_params.h > +++ b/drivers/gpu/drm/i915/i915_params.h > @@ -53,7 +53,6 @@ > func(int, edp_vswing); \ > func(int, reset); \ > func(unsigned int, inject_load_failure); \ > - func(int, enable_dpcd_backlight); \ > /* leave bools at the end to not create holes */ \ > func(bool, alpha_support); \ > func(bool, enable_cmd_parser); \ > diff --git a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c > b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c > index b25cd88fc1c5..f32dec02e540 100644 > --- a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c > +++ b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c > @@ -277,66 +277,15 @@ intel_dp_aux_display_control_capable(struct > intel_connector *connector) > /* Check the eDP Display control capabilities registers to determine > if > * the panel can support backlight control over the aux channel > */ > - if ((intel_dp->edp_dpcd[1] & DP_EDP_TCON_BACKLIGHT_ADJUSTMENT_CAP) && > - (intel_dp->edp_dpcd[2] & > DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP)) { > + if (intel_dp->edp_dpcd[1] & DP_EDP_TCON_BACKLIGHT_ADJUSTMENT_CAP && > + (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_AUX_SET_CAP) > && > + !(intel_dp->edp_dpcd[2] & > DP_EDP_BACKLIGHT_BRIGHTNESS_PWM_PIN_CAP)) { > DRM_DEBUG_KMS("AUX Backlight Control Supported!\n"); > return true; > } > return false; > } > > -/* > - * Heuristic function whether we should use AUX for backlight adjustment or > not. > - * > - * We should use AUX for backlight brightness adjustment if panel doesn't > this > - * via PWM pin or using AUX is better than using PWM pin. > - * > - * The heuristic to determine that using AUX pin is better than using PWM > pin is > - * that the panel support any of the feature list here. > - * - Regional backlight brightness adjustment > - * - Backlight PWM frequency set > - * - More than 8 bits resolution of brightness level > - * - Backlight enablement via AUX and not by BL_ENABLE pin > - * > - * If all above are not true, assume that using PWM pin is better. > - */ > -static bool > -intel_dp_aux_display_control_heuristic(struct intel_connector *connector) > -{ > - struct intel_dp *intel_dp = > enc_to_intel_dp(&connector->encoder->base); > - uint8_t reg_val; > - > - /* Panel doesn't support adjusting backlight brightness via PWN pin */ > - if (!(intel_dp->edp_dpcd[2] & > DP_EDP_BACKLIGHT_BRIGHTNESS_PWM_PIN_CAP)) > - return true; > - > - /* Panel supports regional backlight brightness adjustment */ > - if (drm_dp_dpcd_readb(&intel_dp->aux, DP_EDP_GENERAL_CAP_3, > - ®_val) != 1) { > - DRM_DEBUG_KMS("Failed to read DPCD register 0x%x\n", > - DP_EDP_GENERAL_CAP_3); > - return false; > - } > - if (reg_val > 0) > - return true; > - > - /* Panel supports backlight PWM frequency set */ > - if (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_FREQ_AUX_SET_CAP) > - return true; > - > - /* Panel supports more than 8 bits resolution of brightness level */ > - if (intel_dp->edp_dpcd[2] & DP_EDP_BACKLIGHT_BRIGHTNESS_BYTE_COUNT) > - return true; > - > - /* Panel supports enabling backlight via AUX but not by BL_ENABLE pin > */ > - if ((intel_dp->edp_dpcd[1] & DP_EDP_BACKLIGHT_AUX_ENABLE_CAP) && > - !(intel_dp->edp_dpcd[1] & DP_EDP_BACKLIGHT_PIN_ENABLE_CAP)) > - return true; > - > - return false; > - > -} > - > int intel_dp_aux_init_backlight_funcs(struct intel_connector > *intel_connector) > { > struct intel_panel *panel = &intel_connector->panel; > @@ -347,10 +296,6 @@ int intel_dp_aux_init_backlight_funcs(struct > intel_connector *intel_connector) > if (!intel_dp_aux_display_control_capable(intel_connector)) > return -ENODEV; > > - if (i915.enable_dpcd_backlight == -1 && > - !intel_dp_aux_display_control_heuristic(intel_connector)) > - return -ENODEV; > - > panel->backlight.setup = intel_dp_aux_setup_backlight; > panel->backlight.enable = intel_dp_aux_enable_backlight; > panel->backlight.disable = intel_dp_aux_disable_backlight; > -- > 2.13.2 > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/intel-gfx _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx