[PATCH v2 0/5] Add custom brightness curve support

[PATCH v2 0/5] Add custom brightness curve support

[Mario Limonciello]

Some OEMs support custom brightness curves where the ATIF method includes
a collection of data points where the input signal is mapped out to
percentage of luminance. This series shuffles around some code to add in
the ability to do that mapping in amdgpu_dm when brightness is set.

Mario Limonciello (5):
  drm/amd: Copy entire structure in amdgpu_acpi_get_backlight_caps()
  drm/amd: Pass luminance data to amdgpu_dm_backlight_caps
  drm/amd/display: Avoid operating on copies of backlight caps
  drm/amd/display: Add support for custom brightness curve
  drm/amd/display: Add a new dcdebugmask to allow turning off brightness
    curve

 drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c      | 10 +--
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 82 ++++++++++++-------
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h | 20 +++++
 drivers/gpu/drm/amd/include/amd_acpi.h        |  4 +-
 drivers/gpu/drm/amd/include/amd_shared.h      |  4 +
 5 files changed, 84 insertions(+), 36 deletions(-)

-- 
2.48.1

[PATCH v2 1/5] drm/amd: Copy entire structure in amdgpu_acpi_get_backlight_caps()

[Mario Limonciello]

As new members are introduced to the structure copying the entire
structure will help avoid missing them.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
index b8d4e07d2043..515c6f32448d 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
@@ -1277,11 +1277,7 @@ void amdgpu_acpi_get_backlight_caps(struct amdgpu_dm_backlight_caps *caps)
 {
 	struct amdgpu_atif *atif = &amdgpu_acpi_priv.atif;
 
-	caps->caps_valid = atif->backlight_caps.caps_valid;
-	caps->min_input_signal = atif->backlight_caps.min_input_signal;
-	caps->max_input_signal = atif->backlight_caps.max_input_signal;
-	caps->ac_level = atif->backlight_caps.ac_level;
-	caps->dc_level = atif->backlight_caps.dc_level;
+	memcpy(caps, &atif->backlight_caps, sizeof(*caps));
 }
 
 /**
-- 
2.48.1

[PATCH v2 2/5] drm/amd: Pass luminance data to amdgpu_dm_backlight_caps

[Mario Limonciello]

The ATIF method on some systems will provide a backlight curve. Pass
this curve into amdgpu_dm add it to the structures.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
v2:
 * Keep ACPI and DM structures separate
 * Add static asserts to ensure structures remain in sync
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c      |  4 ++++
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h | 20 +++++++++++++++++++
 drivers/gpu/drm/amd/include/amd_acpi.h        |  4 +++-
 3 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
index 515c6f32448d..b7f8f2ff143d 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
@@ -394,6 +394,10 @@ static int amdgpu_atif_query_backlight_caps(struct amdgpu_atif *atif)
 			characteristics.max_input_signal;
 	atif->backlight_caps.ac_level = characteristics.ac_level;
 	atif->backlight_caps.dc_level = characteristics.dc_level;
+	atif->backlight_caps.data_points = characteristics.number_of_points;
+	memcpy(atif->backlight_caps.luminance_data,
+	       characteristics.data_points,
+	       sizeof(atif->backlight_caps.luminance_data));
 out:
 	kfree(info);
 	return err;
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
index f3bc00e587ad..85b64c457ed6 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
@@ -151,6 +151,18 @@ struct idle_workqueue {
 	bool running;
 };
 
+#define MAX_LUMINANCE_DATA_POINTS 99
+
+/**
+ * struct amdgpu_dm_luminance_data - Custom luminance data
+ * @luminance: Luminance in percent
+ * @input_signal: Input signal in range 0-255
+ */
+struct amdgpu_dm_luminance_data {
+	u8 luminance;
+	u8 input_signal;
+} __packed;
+
 /**
  * struct amdgpu_dm_backlight_caps - Information about backlight
  *
@@ -195,6 +207,14 @@ struct amdgpu_dm_backlight_caps {
 	 * @dc_level: the default brightness if booted on DC
 	 */
 	u8 dc_level;
+	/**
+	 * @data_points: the number of custom luminance data points
+	 */
+	u8 data_points;
+	/**
+	 * @luminance_data: custom luminance data
+	 */
+	struct amdgpu_dm_luminance_data luminance_data[MAX_LUMINANCE_DATA_POINTS];
 };
 
 /**
diff --git a/drivers/gpu/drm/amd/include/amd_acpi.h b/drivers/gpu/drm/amd/include/amd_acpi.h
index 2d089d30518f..06badbf0c5b9 100644
--- a/drivers/gpu/drm/amd/include/amd_acpi.h
+++ b/drivers/gpu/drm/amd/include/amd_acpi.h
@@ -61,7 +61,7 @@ struct atif_qbtc_arguments {
 
 struct atif_qbtc_data_point {
 	u8 luminance;		/* luminance in percent */
-	u8 ipnut_signal;	/* input signal in range 0-255 */
+	u8 input_signal;	/* input signal in range 0-255 */
 } __packed;
 
 struct atif_qbtc_output {
@@ -75,6 +75,8 @@ struct atif_qbtc_output {
 	u8 number_of_points;	/* number of data points */
 	struct atif_qbtc_data_point data_points[ATIF_QBTC_MAX_DATA_POINTS];
 } __packed;
+static_assert(ATIF_QBTC_MAX_DATA_POINTS == MAX_LUMINANCE_DATA_POINTS);
+static_assert(sizeof(struct atif_qbtc_data_point) == sizeof(struct amdgpu_dm_luminance_data));
 
 #define ATIF_NOTIFY_MASK	0x3
 #define ATIF_NOTIFY_NONE	0
-- 
2.48.1

[PATCH v2 3/5] drm/amd/display: Avoid operating on copies of backlight caps

[Mario Limonciello]

Making a copy of the backlight caps structure between uses is unnecessary.
Refer to pointers to the same structure when using it.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
v2:
 * Add fix for !CONFIG_ACPI
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 52 ++++++++-----------
 1 file changed, 22 insertions(+), 30 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index badd8fa2099c..61d626914590 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -4700,48 +4700,40 @@ static int amdgpu_dm_mode_config_init(struct amdgpu_device *adev)
 static void amdgpu_dm_update_backlight_caps(struct amdgpu_display_manager *dm,
 					    int bl_idx)
 {
-#if defined(CONFIG_ACPI)
-	struct amdgpu_dm_backlight_caps caps;
+	struct amdgpu_dm_backlight_caps *caps = &dm->backlight_caps[bl_idx];
 
-	memset(&caps, 0, sizeof(caps));
-
-	if (dm->backlight_caps[bl_idx].caps_valid)
+	if (caps->caps_valid)
 		return;
 
-	amdgpu_acpi_get_backlight_caps(&caps);
+#if defined(CONFIG_ACPI)
+	amdgpu_acpi_get_backlight_caps(caps);
 
 	/* validate the firmware value is sane */
-	if (caps.caps_valid) {
-		int spread = caps.max_input_signal - caps.min_input_signal;
+	if (caps->caps_valid) {
+		int spread = caps->max_input_signal - caps->min_input_signal;
 
-		if (caps.max_input_signal > AMDGPU_DM_DEFAULT_MAX_BACKLIGHT ||
-		    caps.min_input_signal < 0 ||
+		if (caps->max_input_signal > AMDGPU_DM_DEFAULT_MAX_BACKLIGHT ||
+		    caps->min_input_signal < 0 ||
 		    spread > AMDGPU_DM_DEFAULT_MAX_BACKLIGHT ||
 		    spread < AMDGPU_DM_MIN_SPREAD) {
 			DRM_DEBUG_KMS("DM: Invalid backlight caps: min=%d, max=%d\n",
-				      caps.min_input_signal, caps.max_input_signal);
-			caps.caps_valid = false;
+				      caps->min_input_signal, caps->max_input_signal);
+			caps->caps_valid = false;
 		}
 	}
 
-	if (caps.caps_valid) {
-		dm->backlight_caps[bl_idx].caps_valid = true;
-		if (caps.aux_support)
-			return;
-		dm->backlight_caps[bl_idx].min_input_signal = caps.min_input_signal;
-		dm->backlight_caps[bl_idx].max_input_signal = caps.max_input_signal;
-	} else {
-		dm->backlight_caps[bl_idx].min_input_signal =
-				AMDGPU_DM_DEFAULT_MIN_BACKLIGHT;
-		dm->backlight_caps[bl_idx].max_input_signal =
-				AMDGPU_DM_DEFAULT_MAX_BACKLIGHT;
+	if (!caps->caps_valid) {
+		caps->min_input_signal = AMDGPU_DM_DEFAULT_MIN_BACKLIGHT;
+		caps->max_input_signal = AMDGPU_DM_DEFAULT_MAX_BACKLIGHT;
+		caps->caps_valid = true;
 	}
 #else
-	if (dm->backlight_caps[bl_idx].aux_support)
+	if (caps->aux_support)
 		return;
 
-	dm->backlight_caps[bl_idx].min_input_signal = AMDGPU_DM_DEFAULT_MIN_BACKLIGHT;
-	dm->backlight_caps[bl_idx].max_input_signal = AMDGPU_DM_DEFAULT_MAX_BACKLIGHT;
+	caps->min_input_signal = AMDGPU_DM_DEFAULT_MIN_BACKLIGHT;
+	caps->max_input_signal = AMDGPU_DM_DEFAULT_MAX_BACKLIGHT;
+	caps->caps_valid = true;
 #endif
 }
 
@@ -4795,19 +4787,19 @@ static void amdgpu_dm_backlight_set_level(struct amdgpu_display_manager *dm,
 					 int bl_idx,
 					 u32 user_brightness)
 {
-	struct amdgpu_dm_backlight_caps caps;
+	struct amdgpu_dm_backlight_caps *caps;
 	struct dc_link *link;
 	u32 brightness;
 	bool rc, reallow_idle = false;
 
 	amdgpu_dm_update_backlight_caps(dm, bl_idx);
-	caps = dm->backlight_caps[bl_idx];
+	caps = &dm->backlight_caps[bl_idx];
 
 	dm->brightness[bl_idx] = user_brightness;
 	/* update scratch register */
 	if (bl_idx == 0)
 		amdgpu_atombios_scratch_regs_set_backlight_level(dm->adev, dm->brightness[bl_idx]);
-	brightness = convert_brightness_from_user(&caps, dm->brightness[bl_idx]);
+	brightness = convert_brightness_from_user(caps, dm->brightness[bl_idx]);
 	link = (struct dc_link *)dm->backlight_link[bl_idx];
 
 	/* Change brightness based on AUX property */
@@ -4817,7 +4809,7 @@ static void amdgpu_dm_backlight_set_level(struct amdgpu_display_manager *dm,
 		reallow_idle = true;
 	}
 
-	if (caps.aux_support) {
+	if (caps->aux_support) {
 		rc = dc_link_set_backlight_level_nits(link, true, brightness,
 						      AUX_BL_DEFAULT_TRANSITION_TIME_MS);
 		if (!rc)
-- 
2.48.1

[PATCH v2 4/5] drm/amd/display: Add support for custom brightness curve

[Mario Limonciello]

Some systems specify in the firmware a brightness curve that better
reflects the characteristics of the panel used. This is done in the
form of data points and matching luminance percentage.

When converting a userspace requested brightness value use that curve
to convert to a firmware intended brightness value.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 25 +++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 61d626914590..b252c67f2bc4 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -4759,10 +4759,35 @@ static u32 convert_brightness_from_user(const struct amdgpu_dm_backlight_caps *c
 					uint32_t brightness)
 {
 	unsigned int min, max;
+	u8 prev_signal = 0, prev_lum = 0;
 
 	if (!get_brightness_range(caps, &min, &max))
 		return brightness;
 
+	for (int i = 0; i < caps->data_points; i++) {
+		u8 signal, lum;
+
+		signal = caps->luminance_data[i].input_signal;
+		lum = caps->luminance_data[i].luminance;
+
+		/*
+		 * brightness == signal: luminance is percent numerator
+		 * brightness < signal: interpolate between previous and current luminance numerator
+		 * brightness > signal: find next data point
+		 */
+		if (brightness < signal)
+			lum = prev_lum + DIV_ROUND_CLOSEST((lum - prev_lum) *
+							   (brightness - prev_signal),
+							   signal - prev_signal);
+		else if (brightness > signal) {
+			prev_signal = signal;
+			prev_lum = lum;
+			continue;
+		}
+		brightness = DIV_ROUND_CLOSEST(lum * brightness, 101);
+		break;
+	}
+
 	// Rescale 0..255 to min..max
 	return min + DIV_ROUND_CLOSEST((max - min) * brightness,
 				       AMDGPU_MAX_BL_LEVEL);
-- 
2.48.1

[PATCH v2 5/5] drm/amd/display: Add a new dcdebugmask to allow turning off brightness curve

[Mario Limonciello]

Upgrading the kernel may cause some systems that were previously not using
a firmware specified brightness curve to use one.

In the event of problems with this curve (for example an interpolation
error) add a new dcdebugmask value that can be used to turn it off.  Also
add an info message to show that custom brightness curves are currently in
use.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 5 +++++
 drivers/gpu/drm/amd/include/amd_shared.h          | 4 ++++
 2 files changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index b252c67f2bc4..63b66e2c9ab9 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -4767,6 +4767,9 @@ static u32 convert_brightness_from_user(const struct amdgpu_dm_backlight_caps *c
 	for (int i = 0; i < caps->data_points; i++) {
 		u8 signal, lum;
 
+		if (amdgpu_dc_debug_mask & DC_DISABLE_CUSTOM_BRIGHTNESS_CURVE)
+			break;
+
 		signal = caps->luminance_data[i].input_signal;
 		lum = caps->luminance_data[i].luminance;
 
@@ -4951,6 +4954,8 @@ amdgpu_dm_register_backlight_device(struct amdgpu_dm_connector *aconnector)
 	} else
 		props.brightness = AMDGPU_MAX_BL_LEVEL;
 
+	if (caps.data_points && !(amdgpu_dc_debug_mask & DC_DISABLE_CUSTOM_BRIGHTNESS_CURVE))
+		drm_info(drm, "Using custom brightness curve\n");
 	props.max_brightness = AMDGPU_MAX_BL_LEVEL;
 	props.type = BACKLIGHT_RAW;
 
diff --git a/drivers/gpu/drm/amd/include/amd_shared.h b/drivers/gpu/drm/amd/include/amd_shared.h
index c0538763ec1a..485b713cfad0 100644
--- a/drivers/gpu/drm/amd/include/amd_shared.h
+++ b/drivers/gpu/drm/amd/include/amd_shared.h
@@ -354,6 +354,10 @@ enum DC_DEBUG_MASK {
 	 * @DC_DISABLE_SUBVP: If set, disable DCN Sub-Viewport feature in amdgpu driver.
 	 */
 	DC_DISABLE_SUBVP = 0x20000,
+	/**
+	 * @DC_DISABLE_CUSTOM_BRIGHTNESS_CURVE: If set, disable support for custom brightness curves
+	 */
+	DC_DISABLE_CUSTOM_BRIGHTNESS_CURVE = 0x40000,
 };
 
 enum amd_dpm_forced_level;
-- 
2.48.1

Re: [PATCH v2 2/5] drm/amd: Pass luminance data to amdgpu_dm_backlight_caps

[Alex Hung]

Reviewed-by: Alex Hung <alex.hung@amd.com>

On 2/28/25 11:51, Mario Limonciello wrote:
> The ATIF method on some systems will provide a backlight curve. Pass
> this curve into amdgpu_dm add it to the structures.
> 
> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
> ---
> v2:
>   * Keep ACPI and DM structures separate
>   * Add static asserts to ensure structures remain in sync
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c      |  4 ++++
>   .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h | 20 +++++++++++++++++++
>   drivers/gpu/drm/amd/include/amd_acpi.h        |  4 +++-
>   3 files changed, 27 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> index 515c6f32448d..b7f8f2ff143d 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> @@ -394,6 +394,10 @@ static int amdgpu_atif_query_backlight_caps(struct amdgpu_atif *atif)
>   			characteristics.max_input_signal;
>   	atif->backlight_caps.ac_level = characteristics.ac_level;
>   	atif->backlight_caps.dc_level = characteristics.dc_level;
> +	atif->backlight_caps.data_points = characteristics.number_of_points;
> +	memcpy(atif->backlight_caps.luminance_data,
> +	       characteristics.data_points,
> +	       sizeof(atif->backlight_caps.luminance_data));
>   out:
>   	kfree(info);
>   	return err;
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
> index f3bc00e587ad..85b64c457ed6 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
> @@ -151,6 +151,18 @@ struct idle_workqueue {
>   	bool running;
>   };
>   
> +#define MAX_LUMINANCE_DATA_POINTS 99
> +
> +/**
> + * struct amdgpu_dm_luminance_data - Custom luminance data
> + * @luminance: Luminance in percent
> + * @input_signal: Input signal in range 0-255
> + */
> +struct amdgpu_dm_luminance_data {
> +	u8 luminance;
> +	u8 input_signal;
> +} __packed;
> +
>   /**
>    * struct amdgpu_dm_backlight_caps - Information about backlight
>    *
> @@ -195,6 +207,14 @@ struct amdgpu_dm_backlight_caps {
>   	 * @dc_level: the default brightness if booted on DC
>   	 */
>   	u8 dc_level;
> +	/**
> +	 * @data_points: the number of custom luminance data points
> +	 */
> +	u8 data_points;
> +	/**
> +	 * @luminance_data: custom luminance data
> +	 */
> +	struct amdgpu_dm_luminance_data luminance_data[MAX_LUMINANCE_DATA_POINTS];
>   };
>   
>   /**
> diff --git a/drivers/gpu/drm/amd/include/amd_acpi.h b/drivers/gpu/drm/amd/include/amd_acpi.h
> index 2d089d30518f..06badbf0c5b9 100644
> --- a/drivers/gpu/drm/amd/include/amd_acpi.h
> +++ b/drivers/gpu/drm/amd/include/amd_acpi.h
> @@ -61,7 +61,7 @@ struct atif_qbtc_arguments {
>   
>   struct atif_qbtc_data_point {
>   	u8 luminance;		/* luminance in percent */
> -	u8 ipnut_signal;	/* input signal in range 0-255 */
> +	u8 input_signal;	/* input signal in range 0-255 */
>   } __packed;
>   
>   struct atif_qbtc_output {
> @@ -75,6 +75,8 @@ struct atif_qbtc_output {
>   	u8 number_of_points;	/* number of data points */
>   	struct atif_qbtc_data_point data_points[ATIF_QBTC_MAX_DATA_POINTS];
>   } __packed;
> +static_assert(ATIF_QBTC_MAX_DATA_POINTS == MAX_LUMINANCE_DATA_POINTS);
> +static_assert(sizeof(struct atif_qbtc_data_point) == sizeof(struct amdgpu_dm_luminance_data));
>   
>   #define ATIF_NOTIFY_MASK	0x3
>   #define ATIF_NOTIFY_NONE	0

Re: [PATCH v2 3/5] drm/amd/display: Avoid operating on copies of backlight caps

[Alex Hung]

Reviewed-by: Alex Hung <alex.hung@amd.com>

On 2/28/25 11:51, Mario Limonciello wrote:
> Making a copy of the backlight caps structure between uses is unnecessary.
> Refer to pointers to the same structure when using it.
> 
> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
> ---
> v2:
>   * Add fix for !CONFIG_ACPI
> ---
>   .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 52 ++++++++-----------
>   1 file changed, 22 insertions(+), 30 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index badd8fa2099c..61d626914590 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -4700,48 +4700,40 @@ static int amdgpu_dm_mode_config_init(struct amdgpu_device *adev)
>   static void amdgpu_dm_update_backlight_caps(struct amdgpu_display_manager *dm,
>   					    int bl_idx)
>   {
> -#if defined(CONFIG_ACPI)
> -	struct amdgpu_dm_backlight_caps caps;
> +	struct amdgpu_dm_backlight_caps *caps = &dm->backlight_caps[bl_idx];
>   
> -	memset(&caps, 0, sizeof(caps));
> -
> -	if (dm->backlight_caps[bl_idx].caps_valid)
> +	if (caps->caps_valid)
>   		return;
>   
> -	amdgpu_acpi_get_backlight_caps(&caps);
> +#if defined(CONFIG_ACPI)
> +	amdgpu_acpi_get_backlight_caps(caps);
>   
>   	/* validate the firmware value is sane */
> -	if (caps.caps_valid) {
> -		int spread = caps.max_input_signal - caps.min_input_signal;
> +	if (caps->caps_valid) {
> +		int spread = caps->max_input_signal - caps->min_input_signal;
>   
> -		if (caps.max_input_signal > AMDGPU_DM_DEFAULT_MAX_BACKLIGHT ||
> -		    caps.min_input_signal < 0 ||
> +		if (caps->max_input_signal > AMDGPU_DM_DEFAULT_MAX_BACKLIGHT ||
> +		    caps->min_input_signal < 0 ||
>   		    spread > AMDGPU_DM_DEFAULT_MAX_BACKLIGHT ||
>   		    spread < AMDGPU_DM_MIN_SPREAD) {
>   			DRM_DEBUG_KMS("DM: Invalid backlight caps: min=%d, max=%d\n",
> -				      caps.min_input_signal, caps.max_input_signal);
> -			caps.caps_valid = false;
> +				      caps->min_input_signal, caps->max_input_signal);
> +			caps->caps_valid = false;
>   		}
>   	}
>   
> -	if (caps.caps_valid) {
> -		dm->backlight_caps[bl_idx].caps_valid = true;
> -		if (caps.aux_support)
> -			return;
> -		dm->backlight_caps[bl_idx].min_input_signal = caps.min_input_signal;
> -		dm->backlight_caps[bl_idx].max_input_signal = caps.max_input_signal;
> -	} else {
> -		dm->backlight_caps[bl_idx].min_input_signal =
> -				AMDGPU_DM_DEFAULT_MIN_BACKLIGHT;
> -		dm->backlight_caps[bl_idx].max_input_signal =
> -				AMDGPU_DM_DEFAULT_MAX_BACKLIGHT;
> +	if (!caps->caps_valid) {
> +		caps->min_input_signal = AMDGPU_DM_DEFAULT_MIN_BACKLIGHT;
> +		caps->max_input_signal = AMDGPU_DM_DEFAULT_MAX_BACKLIGHT;
> +		caps->caps_valid = true;
>   	}
>   #else
> -	if (dm->backlight_caps[bl_idx].aux_support)
> +	if (caps->aux_support)
>   		return;
>   
> -	dm->backlight_caps[bl_idx].min_input_signal = AMDGPU_DM_DEFAULT_MIN_BACKLIGHT;
> -	dm->backlight_caps[bl_idx].max_input_signal = AMDGPU_DM_DEFAULT_MAX_BACKLIGHT;
> +	caps->min_input_signal = AMDGPU_DM_DEFAULT_MIN_BACKLIGHT;
> +	caps->max_input_signal = AMDGPU_DM_DEFAULT_MAX_BACKLIGHT;
> +	caps->caps_valid = true;
>   #endif
>   }
>   
> @@ -4795,19 +4787,19 @@ static void amdgpu_dm_backlight_set_level(struct amdgpu_display_manager *dm,
>   					 int bl_idx,
>   					 u32 user_brightness)
>   {
> -	struct amdgpu_dm_backlight_caps caps;
> +	struct amdgpu_dm_backlight_caps *caps;
>   	struct dc_link *link;
>   	u32 brightness;
>   	bool rc, reallow_idle = false;
>   
>   	amdgpu_dm_update_backlight_caps(dm, bl_idx);
> -	caps = dm->backlight_caps[bl_idx];
> +	caps = &dm->backlight_caps[bl_idx];
>   
>   	dm->brightness[bl_idx] = user_brightness;
>   	/* update scratch register */
>   	if (bl_idx == 0)
>   		amdgpu_atombios_scratch_regs_set_backlight_level(dm->adev, dm->brightness[bl_idx]);
> -	brightness = convert_brightness_from_user(&caps, dm->brightness[bl_idx]);
> +	brightness = convert_brightness_from_user(caps, dm->brightness[bl_idx]);
>   	link = (struct dc_link *)dm->backlight_link[bl_idx];
>   
>   	/* Change brightness based on AUX property */
> @@ -4817,7 +4809,7 @@ static void amdgpu_dm_backlight_set_level(struct amdgpu_display_manager *dm,
>   		reallow_idle = true;
>   	}
>   
> -	if (caps.aux_support) {
> +	if (caps->aux_support) {
>   		rc = dc_link_set_backlight_level_nits(link, true, brightness,
>   						      AUX_BL_DEFAULT_TRANSITION_TIME_MS);
>   		if (!rc)

Re: [PATCH v2 4/5] drm/amd/display: Add support for custom brightness curve

[Alex Hung]

Reviewed-by: Alex Hung <alex.hung@amd.com>

On 2/28/25 11:51, Mario Limonciello wrote:
> Some systems specify in the firmware a brightness curve that better
> reflects the characteristics of the panel used. This is done in the
> form of data points and matching luminance percentage.
> 
> When converting a userspace requested brightness value use that curve
> to convert to a firmware intended brightness value.
> 
> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
> ---
>   .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 25 +++++++++++++++++++
>   1 file changed, 25 insertions(+)
> 
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index 61d626914590..b252c67f2bc4 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -4759,10 +4759,35 @@ static u32 convert_brightness_from_user(const struct amdgpu_dm_backlight_caps *c
>   					uint32_t brightness)
>   {
>   	unsigned int min, max;
> +	u8 prev_signal = 0, prev_lum = 0;
>   
>   	if (!get_brightness_range(caps, &min, &max))
>   		return brightness;
>   
> +	for (int i = 0; i < caps->data_points; i++) {
> +		u8 signal, lum;
> +
> +		signal = caps->luminance_data[i].input_signal;
> +		lum = caps->luminance_data[i].luminance;
> +
> +		/*
> +		 * brightness == signal: luminance is percent numerator
> +		 * brightness < signal: interpolate between previous and current luminance numerator
> +		 * brightness > signal: find next data point
> +		 */
> +		if (brightness < signal)
> +			lum = prev_lum + DIV_ROUND_CLOSEST((lum - prev_lum) *
> +							   (brightness - prev_signal),
> +							   signal - prev_signal);
> +		else if (brightness > signal) {
> +			prev_signal = signal;
> +			prev_lum = lum;
> +			continue;
> +		}
> +		brightness = DIV_ROUND_CLOSEST(lum * brightness, 101);
> +		break;
> +	}
> +
>   	// Rescale 0..255 to min..max
>   	return min + DIV_ROUND_CLOSEST((max - min) * brightness,
>   				       AMDGPU_MAX_BL_LEVEL);

Re: [PATCH v2 5/5] drm/amd/display: Add a new dcdebugmask to allow turning off brightness curve

[Alex Hung]

Reviewed-by: Alex Hung <alex.hung@amd.com>

On 2/28/25 11:51, Mario Limonciello wrote:
> Upgrading the kernel may cause some systems that were previously not using
> a firmware specified brightness curve to use one.
> 
> In the event of problems with this curve (for example an interpolation
> error) add a new dcdebugmask value that can be used to turn it off.  Also
> add an info message to show that custom brightness curves are currently in
> use.
> 
> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
> ---
>   drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 5 +++++
>   drivers/gpu/drm/amd/include/amd_shared.h          | 4 ++++
>   2 files changed, 9 insertions(+)
> 
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index b252c67f2bc4..63b66e2c9ab9 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -4767,6 +4767,9 @@ static u32 convert_brightness_from_user(const struct amdgpu_dm_backlight_caps *c
>   	for (int i = 0; i < caps->data_points; i++) {
>   		u8 signal, lum;
>   
> +		if (amdgpu_dc_debug_mask & DC_DISABLE_CUSTOM_BRIGHTNESS_CURVE)
> +			break;
> +
>   		signal = caps->luminance_data[i].input_signal;
>   		lum = caps->luminance_data[i].luminance;
>   
> @@ -4951,6 +4954,8 @@ amdgpu_dm_register_backlight_device(struct amdgpu_dm_connector *aconnector)
>   	} else
>   		props.brightness = AMDGPU_MAX_BL_LEVEL;
>   
> +	if (caps.data_points && !(amdgpu_dc_debug_mask & DC_DISABLE_CUSTOM_BRIGHTNESS_CURVE))
> +		drm_info(drm, "Using custom brightness curve\n");
>   	props.max_brightness = AMDGPU_MAX_BL_LEVEL;
>   	props.type = BACKLIGHT_RAW;
>   
> diff --git a/drivers/gpu/drm/amd/include/amd_shared.h b/drivers/gpu/drm/amd/include/amd_shared.h
> index c0538763ec1a..485b713cfad0 100644
> --- a/drivers/gpu/drm/amd/include/amd_shared.h
> +++ b/drivers/gpu/drm/amd/include/amd_shared.h
> @@ -354,6 +354,10 @@ enum DC_DEBUG_MASK {
>   	 * @DC_DISABLE_SUBVP: If set, disable DCN Sub-Viewport feature in amdgpu driver.
>   	 */
>   	DC_DISABLE_SUBVP = 0x20000,
> +	/**
> +	 * @DC_DISABLE_CUSTOM_BRIGHTNESS_CURVE: If set, disable support for custom brightness curves
> +	 */
> +	DC_DISABLE_CUSTOM_BRIGHTNESS_CURVE = 0x40000,
>   };
>   
>   enum amd_dpm_forced_level;

Re: [PATCH v2 1/5] drm/amd: Copy entire structure in amdgpu_acpi_get_backlight_caps()

[Alex Hung]

Reviewed-by: Alex Hung <alex.hung@amd.com>

On 2/28/25 11:51, Mario Limonciello wrote:
> As new members are introduced to the structure copying the entire
> structure will help avoid missing them.
> 
> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c | 6 +-----
>   1 file changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> index b8d4e07d2043..515c6f32448d 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> @@ -1277,11 +1277,7 @@ void amdgpu_acpi_get_backlight_caps(struct amdgpu_dm_backlight_caps *caps)
>   {
>   	struct amdgpu_atif *atif = &amdgpu_acpi_priv.atif;
>   
> -	caps->caps_valid = atif->backlight_caps.caps_valid;
> -	caps->min_input_signal = atif->backlight_caps.min_input_signal;
> -	caps->max_input_signal = atif->backlight_caps.max_input_signal;
> -	caps->ac_level = atif->backlight_caps.ac_level;
> -	caps->dc_level = atif->backlight_caps.dc_level;
> +	memcpy(caps, &atif->backlight_caps, sizeof(*caps));
>   }
>   
>   /**