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From: =?utf-8?q?Thomas_Wei=C3=9Fschuh?= <linux@weissschuh.net>
Date: Wed, 31 Jul 2024 19:00:46 +0200
Subject: [PATCH v3 1/2] drm/connector: add
 drm_connector_get_cmdline_min_brightness_override()
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To: Alex Deucher <alexander.deucher@amd.com>,
 =?utf-8?q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>,
 David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
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 Maxime Ripard <mripard@kernel.org>, Thomas Zimmermann <tzimmermann@suse.de>,
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 Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>,
 Mario Limonciello <mario.limonciello@amd.com>,
 Matt Hartley <matt.hartley@gmail.com>, Kieran Levin <ktl@framework.net>,
 Hans de Goede <hdegoede@redhat.com>, Xinhui Pan <Xinhui.Pan@amd.com>
Cc: amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
 linux-kernel@vger.kernel.org, Dustin Howett <dustin@howett.net>,
 =?utf-8?q?Thomas_Wei=C3=9Fschuh?= <linux@weissschuh.net>
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Add a helper which can read a overridden minimum backlight value from the
kernel cmdline.
This is useful if the minimum backlight as reported by machines VBT
does not match the user expectations.

As an example, the minimum backlight brightness on the Framework 13
matte panel is too high.

Signed-off-by: Thomas Wei=C3=9Fschuh <linux@weissschuh.net>
---
 drivers/gpu/drm/drm_connector.c | 34 ++++++++++++++++++++++++++++++++++
 include/drm/drm_connector.h     |  2 ++
 2 files changed, 36 insertions(+)

diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connecto=
r.c
index ab6ab7ff7ea8..d0b3d5d6c7c2 100644
--- a/drivers/gpu/drm/drm_connector.c
+++ b/drivers/gpu/drm/drm_connector.c
@@ -34,6 +34,7 @@
 #include <drm/drm_utils.h>
=20
 #include <linux/property.h>
+#include <linux/string.h>
 #include <linux/uaccess.h>
=20
 #include <video/cmdline.h>
@@ -3399,3 +3400,36 @@ struct drm_tile_group *drm_mode_create_tile_group(st=
ruct drm_device *dev,
 	return tg;
 }
 EXPORT_SYMBOL(drm_mode_create_tile_group);
+
+/**
+ * drm_connector_get_cmdline_min_brightness_override - read an overridden
+ * minimum brightness value from the cmdline
+ * @connector: connector to query
+ *
+ * Read an minimum brightness override from the kernel cmdline if present.
+ * The parameter takes the form "video=3DCONNECTOR_NAME:min-brightness=3DV=
ALUE".
+ *
+ * RETURNS:
+ * negative error or override value in the range [0, 255]
+ */
+int drm_connector_get_cmdline_min_brightness_override(struct drm_connector=
 *connector)
+{
+	const char *option, *value_str;
+	int err;
+	u8 val;
+
+	option =3D video_get_options(connector->name);
+	if (!option)
+		return -ENOENT;
+
+	value_str =3D option + str_has_prefix(option, "min-brightness=3D");
+	if (value_str =3D=3D option)
+		return -EINVAL;
+
+	err =3D kstrtou8(value_str, 10, &val);
+	if (err)
+		return err;
+
+	return val;
+}
+EXPORT_SYMBOL_GPL(drm_connector_get_cmdline_min_brightness_override);
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index c754651044d4..64d86604cc6e 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -2357,6 +2357,8 @@ bool drm_connector_has_possible_encoder(struct drm_co=
nnector *connector,
 					struct drm_encoder *encoder);
 const char *drm_get_colorspace_name(enum drm_colorspace colorspace);
=20
+int drm_connector_get_cmdline_min_brightness_override(struct drm_connector=
 *connector);
+
 /**
  * drm_for_each_connector_iter - connector_list iterator macro
  * @connector: &struct drm_connector pointer used as cursor

--=20
2.46.0

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From: =?utf-8?q?Thomas_Wei=C3=9Fschuh?= <linux@weissschuh.net>
Date: Wed, 31 Jul 2024 19:00:47 +0200
Subject: [PATCH v3 2/2] drm/amd/display: implement minimum brightness
 override
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To: Alex Deucher <alexander.deucher@amd.com>,
 =?utf-8?q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>,
 David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
 Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
 Maxime Ripard <mripard@kernel.org>, Thomas Zimmermann <tzimmermann@suse.de>,
 Harry Wentland <harry.wentland@amd.com>, Leo Li <sunpeng.li@amd.com>,
 Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>,
 Mario Limonciello <mario.limonciello@amd.com>,
 Matt Hartley <matt.hartley@gmail.com>, Kieran Levin <ktl@framework.net>,
 Hans de Goede <hdegoede@redhat.com>, Xinhui Pan <Xinhui.Pan@amd.com>
Cc: amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
 linux-kernel@vger.kernel.org, Dustin Howett <dustin@howett.net>,
 =?utf-8?q?Thomas_Wei=C3=9Fschuh?= <linux@weissschuh.net>
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This is useful if the minimum backlight as reported by machines VBT
does not match the user expectations.

As an example, the minimum backlight brightness on the Framework 13
matte panel is too high.

Signed-off-by: Thomas Wei=C3=9Fschuh <linux@weissschuh.net>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gp=
u/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 7e7929f24ae4..ae15465cacfc 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -3330,6 +3330,7 @@ static void update_connector_ext_caps(struct amdgpu_d=
m_connector *aconnector)
 	struct drm_connector *conn_base;
 	struct amdgpu_device *adev;
 	struct drm_luminance_range_info *luminance_range;
+	int min_input_signal_override;
=20
 	if (aconnector->bl_idx =3D=3D -1 ||
 	    aconnector->dc_link->connector_signal !=3D SIGNAL_TYPE_EDP)
@@ -3364,6 +3365,11 @@ static void update_connector_ext_caps(struct amdgpu_=
dm_connector *aconnector)
 		caps->aux_min_input_signal =3D 0;
 		caps->aux_max_input_signal =3D 512;
 	}
+
+	min_input_signal_override =3D drm_connector_get_cmdline_min_brightness_ov=
erride(conn_base);
+	if (min_input_signal_override >=3D 0)
+		caps->min_input_signal =3D min_input_signal_override;
+
 }
=20
 void amdgpu_dm_update_connector_after_detect(

--=20
2.46.0