[PATCH v4 0/3] drm: Minimum backlight overrides and implementation for amdgpu

[PATCH v4 0/3] drm: Minimum backlight overrides and implementation for amdgpu

[Thomas Weißschuh]

The value of "min_input_signal" returned from ATIF on a Framework AMD 13
is "12". This leads to a fairly bright minimum display backlight.

Introduce a quirk to override "min_input_signal" to "0" which leads to a
much lower minimum brightness, which is still readable even in daylight.

Tested on a Framework AMD 13 BIOS 3.05 and Framework AMD 16.

One solution would be a fixed firmware version, which was announced but
has no timeline.

---
Changes in v4:
- Switch back to v2 implementation
- Add MODULE_DESCRIPTION()
- Simplify quirk infrastructure to only handle min backlight quirks.
  It can be extended if necessary.
- Expand documentation.
- Link to v3: https://lore.kernel.org/r/20240731-amdgpu-min-backlight-quirk-v3-0-46d40bb21a62@weissschuh.net

Changes in v3:
- Switch to cmdline override parameter
- Link to v2: https://lore.kernel.org/r/20240623-amdgpu-min-backlight-quirk-v2-0-cecf7f49da9b@weissschuh.net

Changes in v2:
- Introduce proper drm backlight quirk infrastructure
- Quirk by EDID and DMI instead of only DMI
- Limit quirk to only single Framework 13 matte panel
- Link to v1: https://lore.kernel.org/r/20240610-amdgpu-min-backlight-quirk-v1-1-8459895a5b2a@weissschuh.net

---
Thomas Weißschuh (3):
      drm: Add panel backlight quirks
      drm: panel-backlight-quirks: Add Framework 13 matte panel
      drm/amd/display: Add support for minimum backlight quirk

 Documentation/gpu/drm-kms-helpers.rst             |  3 +
 drivers/gpu/drm/Kconfig                           |  4 ++
 drivers/gpu/drm/Makefile                          |  1 +
 drivers/gpu/drm/amd/amdgpu/Kconfig                |  1 +
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 10 +++
 drivers/gpu/drm/drm_panel_backlight_quirks.c      | 77 +++++++++++++++++++++++
 include/drm/drm_utils.h                           |  3 +
 7 files changed, 99 insertions(+)
---
base-commit: d74da846046aeec9333e802f5918bd3261fb5509
change-id: 20240610-amdgpu-min-backlight-quirk-8402fd8e736a

Best regards,
-- 
Thomas Weißschuh <linux@weissschuh.net>

[PATCH v4 1/3] drm: Add panel backlight quirks

[Thomas Weißschuh]

Panels using a PWM-controlled backlight source without an 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: Thomas Weißschuh <linux@weissschuh.net>
---
 Documentation/gpu/drm-kms-helpers.rst        |  3 ++
 drivers/gpu/drm/Kconfig                      |  4 ++
 drivers/gpu/drm/Makefile                     |  1 +
 drivers/gpu/drm/drm_panel_backlight_quirks.c | 69 ++++++++++++++++++++++++++++
 include/drm/drm_utils.h                      |  3 ++
 5 files changed, 80 insertions(+)

diff --git a/Documentation/gpu/drm-kms-helpers.rst b/Documentation/gpu/drm-kms-helpers.rst
index 8435e8621cc0..a26989500129 100644
--- a/Documentation/gpu/drm-kms-helpers.rst
+++ b/Documentation/gpu/drm-kms-helpers.rst
@@ -230,6 +230,9 @@ 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
 ===================================
 
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 6b2c6b91f962..9ebb8cdb535e 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -454,6 +454,10 @@ 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
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 68cc9258ffc4..adf85999aee2 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -92,6 +92,7 @@ drm-$(CONFIG_DRM_PANIC) += drm_panic.o
 obj-$(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
diff --git a/drivers/gpu/drm/drm_panel_backlight_quirks.c b/drivers/gpu/drm/drm_panel_backlight_quirks.c
new file mode 100644
index 000000000000..a88e77db97c5
--- /dev/null
+++ b/drivers/gpu/drm/drm_panel_backlight_quirks.c
@@ -0,0 +1,69 @@
+// 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_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");
diff --git a/include/drm/drm_utils.h b/include/drm/drm_utils.h
index 70775748d243..267711028dd4 100644
--- a/include/drm/drm_utils.h
+++ b/include/drm/drm_utils.h
@@ -11,9 +11,12 @@
 #define __DRM_UTILS_H__
 
 #include <linux/types.h>
+#include <drm/drm_edid.h>
 
 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

-- 
2.46.0

[PATCH v4 2/3] drm: panel-backlight-quirks: Add Framework 13 matte panel

[Thomas Weißschuh]

The value of "min_input_signal" returned from ATIF on a Framework AMD 13
is "12". This leads to a fairly bright minimum display backlight.

Add a quirk to override that the minimum backlight PWM to "0" which
leads to a much lower minimum brightness, which is still visible.

Tested on a Framework AMD 13 BIOS 3.05 with the matte panel.

Link: https://community.frame.work/t/25711/9
Link: https://community.frame.work/t/47036
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 drivers/gpu/drm/drm_panel_backlight_quirks.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/drm_panel_backlight_quirks.c b/drivers/gpu/drm/drm_panel_backlight_quirks.c
index a88e77db97c5..c58344cdbb6e 100644
--- a/drivers/gpu/drm/drm_panel_backlight_quirks.c
+++ b/drivers/gpu/drm/drm_panel_backlight_quirks.c
@@ -16,6 +16,14 @@ struct drm_panel_min_backlight_quirk {
 };
 
 static const struct drm_panel_min_backlight_quirk drm_panel_min_backlight_quirks[] = {
+	/* 13 inch matte panel */
+	{
+		.dmi_match.field = DMI_BOARD_VENDOR,
+		.dmi_match.value = "Framework",
+		.ident.panel_id = drm_edid_encode_panel_id('B', 'O', 'E', 0x0bca),
+		.ident.name = "NE135FBM-N41",
+		.min_brightness = 0,
+	},
 };
 
 static bool drm_panel_min_backlight_quirk_matches(const struct drm_panel_min_backlight_quirk *quirk,

-- 
2.46.0

[PATCH v4 3/3] drm/amd/display: Add support for minimum backlight quirk

[Thomas Weißschuh]

Not all platforms provide correct PWM backlight capabilities through ATIF.
Use the generic drm panel minimum backlight quirk infrastructure to
override the capabilities where necessary.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 drivers/gpu/drm/amd/amdgpu/Kconfig                |  1 +
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 10 ++++++++++
 2 files changed, 11 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/Kconfig b/drivers/gpu/drm/amd/amdgpu/Kconfig
index 0051fb1b437f..655c10aef2e3 100644
--- a/drivers/gpu/drm/amd/amdgpu/Kconfig
+++ b/drivers/gpu/drm/amd/amdgpu/Kconfig
@@ -23,6 +23,7 @@ config DRM_AMDGPU
 	select DRM_BUDDY
 	select DRM_SUBALLOC_HELPER
 	select DRM_EXEC
+	select DRM_PANEL_BACKLIGHT_QUIRKS
 	# amdgpu depends on ACPI_VIDEO when ACPI is enabled, for select to work
 	# ACPI_VIDEO's dependencies must also be selected.
 	select INPUT if ACPI
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 7e7929f24ae4..defa4c869921 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -93,6 +93,7 @@
 #include <drm/drm_fourcc.h>
 #include <drm/drm_edid.h>
 #include <drm/drm_eld.h>
+#include <drm/drm_utils.h>
 #include <drm/drm_vblank.h>
 #include <drm/drm_audio_component.h>
 #include <drm/drm_gem_atomic_helper.h>
@@ -3330,6 +3331,8 @@ static void update_connector_ext_caps(struct amdgpu_dm_connector *aconnector)
 	struct drm_connector *conn_base;
 	struct amdgpu_device *adev;
 	struct drm_luminance_range_info *luminance_range;
+	const struct drm_edid *drm_edid;
+	int min_input_signal_override;
 
 	if (aconnector->bl_idx == -1 ||
 	    aconnector->dc_link->connector_signal != SIGNAL_TYPE_EDP)
@@ -3364,6 +3367,13 @@ static void update_connector_ext_caps(struct amdgpu_dm_connector *aconnector)
 		caps->aux_min_input_signal = 0;
 		caps->aux_max_input_signal = 512;
 	}
+
+	drm_edid = drm_edid_alloc(aconnector->edid,
+				  EDID_LENGTH * (aconnector->edid->extensions + 1));
+	min_input_signal_override = drm_get_panel_min_brightness_quirk(drm_edid);
+	drm_edid_free(drm_edid);
+	if (min_input_signal_override >= 0)
+		caps->min_input_signal = min_input_signal_override;
 }
 
 void amdgpu_dm_update_connector_after_detect(

-- 
2.46.0

Re: [PATCH v4 1/3] drm: Add panel backlight quirks

[Jani Nikula]

On Mon, 12 Aug 2024, Thomas Weißschuh <linux@weissschuh.net> wrote:
> Panels using a PWM-controlled backlight source without an 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: Thomas Weißschuh <linux@weissschuh.net>
> ---
>  Documentation/gpu/drm-kms-helpers.rst        |  3 ++
>  drivers/gpu/drm/Kconfig                      |  4 ++
>  drivers/gpu/drm/Makefile                     |  1 +
>  drivers/gpu/drm/drm_panel_backlight_quirks.c | 69 ++++++++++++++++++++++++++++
>  include/drm/drm_utils.h                      |  3 ++
>  5 files changed, 80 insertions(+)
>
> diff --git a/Documentation/gpu/drm-kms-helpers.rst b/Documentation/gpu/drm-kms-helpers.rst
> index 8435e8621cc0..a26989500129 100644
> --- a/Documentation/gpu/drm-kms-helpers.rst
> +++ b/Documentation/gpu/drm-kms-helpers.rst
> @@ -230,6 +230,9 @@ 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
>  ===================================
>  
> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
> index 6b2c6b91f962..9ebb8cdb535e 100644
> --- a/drivers/gpu/drm/Kconfig
> +++ b/drivers/gpu/drm/Kconfig
> @@ -454,6 +454,10 @@ 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
> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> index 68cc9258ffc4..adf85999aee2 100644
> --- a/drivers/gpu/drm/Makefile
> +++ b/drivers/gpu/drm/Makefile
> @@ -92,6 +92,7 @@ drm-$(CONFIG_DRM_PANIC) += drm_panic.o
>  obj-$(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
> diff --git a/drivers/gpu/drm/drm_panel_backlight_quirks.c b/drivers/gpu/drm/drm_panel_backlight_quirks.c
> new file mode 100644
> index 000000000000..a88e77db97c5
> --- /dev/null
> +++ b/drivers/gpu/drm/drm_panel_backlight_quirks.c
> @@ -0,0 +1,69 @@
> +// 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_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");
> diff --git a/include/drm/drm_utils.h b/include/drm/drm_utils.h
> index 70775748d243..267711028dd4 100644
> --- a/include/drm/drm_utils.h
> +++ b/include/drm/drm_utils.h
> @@ -11,9 +11,12 @@
>  #define __DRM_UTILS_H__
>  
>  #include <linux/types.h>
> +#include <drm/drm_edid.h>

Please prefer forward declarations over includes where possible.

Here,

struct drm_edid;

is sufficient.

BR,
Jani.

>  
>  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

-- 
Jani Nikula, Intel