Commit 22e5c7ae authored by Thomas Weißschuh's avatar Thomas Weißschuh Committed by Mario Limonciello
Browse files

drm: Add panel backlight quirks 



Panels using a PWM-controlled backlight source do not have a standard
way to communicate their valid PWM ranges.
On x86 the ranges are read from ACPI through driver-specific tables.
The built-in ranges are not necessarily correct, or may grow stale if an
older device can be retrofitted with newer panels.

Add a quirk infrastructure with which the minimum valid backlight value
can be maintained as part of the kernel.

Signed-off-by: default avatarThomas Weißschuh <linux@weissschuh.net>
Tested-by: default avatarDustin L. Howett <dustin@howett.net>
Reviewed-by: default avatarMario Limonciello <mario.limonciello@amd.com>
Reviewed-by: default avatarHarry Wentland <harry.wentland@amd.com>
Signed-off-by: default avatarMario Limonciello <mario.limonciello@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241111-amdgpu-min-backlight-quirk-v7-1-f662851fda69@weissschuh.net
parent dbf7986f

Documentation/gpu/drm-kms-helpers.rst

+3 −0
Original line number Diff line number Diff line
@@ -221,6 +221,9 @@ Panel Helper Reference 
.. kernel-doc:: drivers/gpu/drm/drm_panel_orientation_quirks.c

   :export:



.. kernel-doc:: drivers/gpu/drm/drm_panel_backlight_quirks.c

   :export:



Panel Self Refresh Helper Reference

===================================

drivers/gpu/drm/Kconfig

+4 −0
Original line number Diff line number Diff line
@@ -456,6 +456,10 @@ config DRM_HYPERV 
config DRM_EXPORT_FOR_TESTS

	bool



# Separate option as not all DRM drivers use it

config DRM_PANEL_BACKLIGHT_QUIRKS

	tristate



config DRM_LIB_RANDOM

	bool

	default n

drivers/gpu/drm/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -95,6 +95,7 @@ drm-$(CONFIG_DRM_PANIC_SCREEN_QR_CODE) += drm_panic_qr.o 
obj-$(CONFIG_DRM)	+= drm.o



obj-$(CONFIG_DRM_PANEL_ORIENTATION_QUIRKS) += drm_panel_orientation_quirks.o

obj-$(CONFIG_DRM_PANEL_BACKLIGHT_QUIRKS) += drm_panel_backlight_quirks.o



#

# Memory-management helpers

drivers/gpu/drm/drm_panel_backlight_quirks.c

0 → 100644
+70 −0
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// SPDX-License-Identifier: GPL-2.0



#include <linux/array_size.h>

#include <linux/dmi.h>

#include <linux/mod_devicetable.h>

#include <linux/module.h>

#include <drm/drm_edid.h>

#include <drm/drm_utils.h>



struct drm_panel_min_backlight_quirk {

	struct {

		enum dmi_field field;

		const char * const value;

	} dmi_match;

	struct drm_edid_ident ident;

	u8 min_brightness;

};



static const struct drm_panel_min_backlight_quirk drm_panel_min_backlight_quirks[] = {

};



static bool drm_panel_min_backlight_quirk_matches(const struct drm_panel_min_backlight_quirk *quirk,

						  const struct drm_edid *edid)

{

	if (!dmi_match(quirk->dmi_match.field, quirk->dmi_match.value))

		return false;



	if (!drm_edid_match(edid, &quirk->ident))

		return false;



	return true;

}



/**

 * drm_get_panel_min_brightness_quirk - Get minimum supported brightness level for a panel.

 * @edid: EDID of the panel to check

 *

 * This function checks for platform specific (e.g. DMI based) quirks

 * providing info on the minimum backlight brightness for systems where this

 * cannot be probed correctly from the hard-/firm-ware.

 *

 * Returns:

 * A negative error value or

 * an override value in the range [0, 255] representing 0-100% to be scaled to

 * the drivers target range.

 */

int drm_get_panel_min_brightness_quirk(const struct drm_edid *edid)

{

	const struct drm_panel_min_backlight_quirk *quirk;

	size_t i;



	if (!IS_ENABLED(CONFIG_DMI))

		return -ENODATA;



	if (!edid)

		return -EINVAL;



	for (i = 0; i < ARRAY_SIZE(drm_panel_min_backlight_quirks); i++) {

		quirk = &drm_panel_min_backlight_quirks[i];



		if (drm_panel_min_backlight_quirk_matches(quirk, edid))

			return quirk->min_brightness;

	}



	return -ENODATA;

}

EXPORT_SYMBOL(drm_get_panel_min_brightness_quirk);



MODULE_DESCRIPTION("Quirks for panel backlight overrides");

MODULE_LICENSE("GPL");

include/drm/drm_utils.h

+4 −0
Original line number Diff line number Diff line
@@ -12,8 +12,12 @@ 


#include <linux/types.h>



struct drm_edid;



int drm_get_panel_orientation_quirk(int width, int height);



int drm_get_panel_min_brightness_quirk(const struct drm_edid *edid);



signed long drm_timeout_abs_to_jiffies(int64_t timeout_nsec);



#endif