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Commit d2939424 authored by Jani Nikula's avatar Jani Nikula
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Revert "drm/i915: Add heuristic to determine better way to adjust brightness" 

This reverts commit 560a758d.

The DPCD backlight commits regress a Thinkpad X1 Carbon 4th Gen and a
BXT-P (in CI). Enabling dynamic backlight boots to a black screen, and
enabling DPCD backlight leads to a black screen after suspend/resume.

References: http://mid.mail-archive.com/20170706135349.6tu3lz7uehazlnnn@boom
References: http://mid.mail-archive.com/20170627132326.f2q3yn4bh5flji4q@boom
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101619


Reported-by: default avatarDavid Weinehall <david.weinehall@linux.intel.com>
Fixes: 560a758d ("drm/i915: Add heuristic to determine better way to adjust brightness")
Cc: Jenny TC <jenny.tc@intel.com>
Cc: David Weinehall <david.weinehall@linux.intel.com>
Cc: Puthikorn Voravootivat <puthik@chromium.org>
Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: intel-gfx@lists.freedesktop.org
Reviewed-by: default avatarDhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Acked-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: default avatarJani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/f49a89a05f18e90871c2eeadcdcd783ac7961cdf.1500542254.git.jani.nikula@intel.com
parent 7d9a1e41

drivers/gpu/drm/i915/i915_params.c

+3 −4
Original line number Diff line number Diff line
@@ -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,

};
@@ -246,10 +246,9 @@ 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,

drivers/gpu/drm/i915/i915_params.h

+1 −1
Original line number Diff line number Diff line
@@ -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); \
@@ -67,6 +66,7 @@ 
	func(bool, verbose_state_checks); \

	func(bool, nuclear_pageflip); \

	func(bool, enable_dp_mst); \

	func(bool, enable_dpcd_backlight); \

	func(bool, enable_gvt)



#define MEMBER(T, member) T member

drivers/gpu/drm/i915/intel_dp_aux_backlight.c

+3 −58
Original line number Diff line number Diff line
@@ -251,66 +251,15 @@ 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,

			      &reg_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;
@@ -321,10 +270,6 @@ 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;