[Intel-gfx] [PATCH v2] drm/i915/quirk: Add quirk for devices with incorrect PWM frequency

2023-11-10 Thread Allen Ballway
Cyernet T10C has a bad default PWM frequency causing the display to
strobe when the brightness is less than 100%. Create a new quirk to use
the value from the BIOS rather than the default register value.

Signed-off-by: Allen Ballway 
---
V1 -> V2: Fix style issues.

 .../gpu/drm/i915/display/intel_backlight.c|  6 +++--
 drivers/gpu/drm/i915/display/intel_quirks.c   | 26 +++
 drivers/gpu/drm/i915/display/intel_quirks.h   |  1 +
 3 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_backlight.c 
b/drivers/gpu/drm/i915/display/intel_backlight.c
index 2e8f17c045222..b4171952343eb 100644
--- a/drivers/gpu/drm/i915/display/intel_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_backlight.c
@@ -1385,8 +1385,10 @@ static int vlv_setup_backlight(struct intel_connector 
*connector, enum pipe pipe
ctl2 = intel_de_read(i915, VLV_BLC_PWM_CTL2(pipe));
panel->backlight.active_low_pwm = ctl2 & BLM_POLARITY_I965;

-   ctl = intel_de_read(i915, VLV_BLC_PWM_CTL(pipe));
-   panel->backlight.pwm_level_max = ctl >> 16;
+   if (!intel_has_quirk(i915, QUIRK_IGNORE_DEFAULT_PWM_FREQUENCY)) {
+   ctl = intel_de_read(i915, VLV_BLC_PWM_CTL(pipe));
+   panel->backlight.pwm_level_max = ctl >> 16;
+   }

if (!panel->backlight.pwm_level_max)
panel->backlight.pwm_level_max = 
get_backlight_max_vbt(connector);
diff --git a/drivers/gpu/drm/i915/display/intel_quirks.c 
b/drivers/gpu/drm/i915/display/intel_quirks.c
index a280448df771a..ff6cb499428ce 100644
--- a/drivers/gpu/drm/i915/display/intel_quirks.c
+++ b/drivers/gpu/drm/i915/display/intel_quirks.c
@@ -65,6 +65,12 @@ static void quirk_no_pps_backlight_power_hook(struct 
drm_i915_private *i915)
drm_info(>drm, "Applying no pps backlight power quirk\n");
 }

+static void quirk_ignore_default_pwm_frequency(struct drm_i915_private *i915)
+{
+   intel_set_quirk(i915, QUIRK_IGNORE_DEFAULT_PWM_FREQUENCY);
+   drm_info(>drm, "Applying ignore default pwm frequency quirk");
+}
+
 struct intel_quirk {
int device;
int subsystem_vendor;
@@ -90,6 +96,12 @@ static int intel_dmi_no_pps_backlight(const struct 
dmi_system_id *id)
return 1;
 }

+static int intel_dmi_ignore_default_pwm_frequency(const struct dmi_system_id 
*id)
+{
+   DRM_INFO("Default PWM frequency is incorrect and is overridden on 
%s\n", id->ident);
+   return 1;
+}
+
 static const struct intel_dmi_quirk intel_dmi_quirks[] = {
{
.dmi_id_list = &(const struct dmi_system_id[]) {
@@ -136,6 +148,20 @@ static const struct intel_dmi_quirk intel_dmi_quirks[] = {
},
.hook = quirk_no_pps_backlight_power_hook,
},
+   {
+   .dmi_id_list = &(const struct dmi_system_id[]) {
+   {
+   .callback = 
intel_dmi_ignore_default_pwm_frequency,
+   .ident = "Cybernet T10C Tablet",
+   .matches = {DMI_EXACT_MATCH(DMI_BOARD_VENDOR,
+   "Cybernet 
Manufacturing Inc."),
+   DMI_EXACT_MATCH(DMI_BOARD_NAME, 
"T10C Tablet"),
+   },
+   },
+   { }
+   },
+   .hook = quirk_ignore_default_pwm_frequency,
+   },
 };

 static struct intel_quirk intel_quirks[] = {
diff --git a/drivers/gpu/drm/i915/display/intel_quirks.h 
b/drivers/gpu/drm/i915/display/intel_quirks.h
index 10a4d163149fd..ca34dacf0c242 100644
--- a/drivers/gpu/drm/i915/display/intel_quirks.h
+++ b/drivers/gpu/drm/i915/display/intel_quirks.h
@@ -17,6 +17,7 @@ enum intel_quirk_id {
QUIRK_INVERT_BRIGHTNESS,
QUIRK_LVDS_SSC_DISABLE,
QUIRK_NO_PPS_BACKLIGHT_POWER_HOOK,
+   QUIRK_IGNORE_DEFAULT_PWM_FREQUENCY,
 };

 void intel_init_quirks(struct drm_i915_private *i915);
--
2.42.0.869.gea05f2083d-goog



[Intel-gfx] [PATCH] drm/i915/quirk: Add quirk for devices with incorrect PWM frequency

2023-10-17 Thread Allen Ballway
Cyernet T10C has a bad default PWM frequency causing the display to
strobe when the brightness is less than 100%. Create a new quirk to use
the value from the BIOS rather than the default register value.

Signed-off-by: Allen Ballway 

---

 .../gpu/drm/i915/display/intel_backlight.c|  3 ++-
 drivers/gpu/drm/i915/display/intel_quirks.c   | 26 +++
 drivers/gpu/drm/i915/display/intel_quirks.h   |  1 +
 3 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/display/intel_backlight.c 
b/drivers/gpu/drm/i915/display/intel_backlight.c
index 2e8f17c045222..c4dcfece9deca 100644
--- a/drivers/gpu/drm/i915/display/intel_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_backlight.c
@@ -1388,7 +1388,8 @@ static int vlv_setup_backlight(struct intel_connector 
*connector, enum pipe pipe
ctl = intel_de_read(i915, VLV_BLC_PWM_CTL(pipe));
panel->backlight.pwm_level_max = ctl >> 16;

-   if (!panel->backlight.pwm_level_max)
+   if (!panel->backlight.pwm_level_max ||
+   intel_has_quirk(i915, QUIRK_IGNORE_DEFAULT_PWM_FREQUENCY))
panel->backlight.pwm_level_max = 
get_backlight_max_vbt(connector);

if (!panel->backlight.pwm_level_max)
diff --git a/drivers/gpu/drm/i915/display/intel_quirks.c 
b/drivers/gpu/drm/i915/display/intel_quirks.c
index a280448df771a..ff6cb499428ce 100644
--- a/drivers/gpu/drm/i915/display/intel_quirks.c
+++ b/drivers/gpu/drm/i915/display/intel_quirks.c
@@ -65,6 +65,12 @@ static void quirk_no_pps_backlight_power_hook(struct 
drm_i915_private *i915)
drm_info(>drm, "Applying no pps backlight power quirk\n");
 }

+static void quirk_ignore_default_pwm_frequency(struct drm_i915_private *i915)
+{
+   intel_set_quirk(i915, QUIRK_IGNORE_DEFAULT_PWM_FREQUENCY);
+   drm_info(>drm, "Applying ignore default pwm frequency quirk");
+}
+
 struct intel_quirk {
int device;
int subsystem_vendor;
@@ -90,6 +96,12 @@ static int intel_dmi_no_pps_backlight(const struct 
dmi_system_id *id)
return 1;
 }

+static int intel_dmi_ignore_default_pwm_frequency(const struct dmi_system_id 
*id)
+{
+   DRM_INFO("Default PWM frequency is incorrect and is overridden on 
%s\n", id->ident);
+   return 1;
+}
+
 static const struct intel_dmi_quirk intel_dmi_quirks[] = {
{
.dmi_id_list = &(const struct dmi_system_id[]) {
@@ -136,6 +148,20 @@ static const struct intel_dmi_quirk intel_dmi_quirks[] = {
},
.hook = quirk_no_pps_backlight_power_hook,
},
+   {
+   .dmi_id_list = &(const struct dmi_system_id[]) {
+   {
+   .callback = 
intel_dmi_ignore_default_pwm_frequency,
+   .ident = "Cybernet T10C Tablet",
+   .matches = {DMI_EXACT_MATCH(DMI_BOARD_VENDOR,
+   "Cybernet 
Manufacturing Inc."),
+   DMI_EXACT_MATCH(DMI_BOARD_NAME, 
"T10C Tablet"),
+   },
+   },
+   { }
+   },
+   .hook = quirk_ignore_default_pwm_frequency,
+   },
 };

 static struct intel_quirk intel_quirks[] = {
diff --git a/drivers/gpu/drm/i915/display/intel_quirks.h 
b/drivers/gpu/drm/i915/display/intel_quirks.h
index 10a4d163149fd..70589505e5a0e 100644
--- a/drivers/gpu/drm/i915/display/intel_quirks.h
+++ b/drivers/gpu/drm/i915/display/intel_quirks.h
@@ -17,6 +17,7 @@ enum intel_quirk_id {
QUIRK_INVERT_BRIGHTNESS,
QUIRK_LVDS_SSC_DISABLE,
QUIRK_NO_PPS_BACKLIGHT_POWER_HOOK,
+   QUIRK_IGNORE_DEFAULT_PWM_FREQUENCY
 };

 void intel_init_quirks(struct drm_i915_private *i915);
--
2.42.0.655.g421f12c284-goog



[Intel-gfx] [PATCH v3 RESEND] drm/i915/quirk: Add quirk for devices that cannot be dimmed

2023-08-08 Thread Allen Ballway
Cybernet T10C cannot be dimmed without the backlight strobing. Create a
new quirk to lock the minimum brightness to the highest supported value.
This aligns the device with its behavior on Windows, which will not
lower the brightness below maximum.

Signed-off-by: Allen Ballway 
---
V2 -> V3: Fix typo.
V1 -> V2: Fix style issue.

.../gpu/drm/i915/display/intel_backlight.c|  5 
 drivers/gpu/drm/i915/display/intel_quirks.c   | 27 +++
 drivers/gpu/drm/i915/display/intel_quirks.h   |  1 +
 3 files changed, 33 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_backlight.c 
b/drivers/gpu/drm/i915/display/intel_backlight.c
index 2e8f17c045222..f015563d3ebd5 100644
--- a/drivers/gpu/drm/i915/display/intel_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_backlight.c
@@ -1192,6 +1192,11 @@ static u32 get_backlight_min_vbt(struct intel_connector 
*connector)

drm_WARN_ON(>drm, panel->backlight.pwm_level_max == 0);

+   if (intel_has_quirk(i915, QUIRK_NO_DIM)) {
+   /* Cannot dim backlight, set minimum to highest value */
+   return panel->backlight.pwm_level_max - 1;
+   }
+
/*
 * XXX: If the vbt value is 255, it makes min equal to max, which leads
 * to problems. There are such machines out there. Either our
diff --git a/drivers/gpu/drm/i915/display/intel_quirks.c 
b/drivers/gpu/drm/i915/display/intel_quirks.c
index a280448df771a..910c95840a539 100644
--- a/drivers/gpu/drm/i915/display/intel_quirks.c
+++ b/drivers/gpu/drm/i915/display/intel_quirks.c
@@ -65,6 +65,12 @@ static void quirk_no_pps_backlight_power_hook(struct 
drm_i915_private *i915)
drm_info(>drm, "Applying no pps backlight power quirk\n");
 }

+static void quirk_no_dim(struct drm_i915_private *i915)
+{
+   intel_set_quirk(i915, QUIRK_NO_DIM);
+   drm_info(>drm, "Applying no dim quirk\n");
+}
+
 struct intel_quirk {
int device;
int subsystem_vendor;
@@ -90,6 +96,12 @@ static int intel_dmi_no_pps_backlight(const struct 
dmi_system_id *id)
return 1;
 }

+static int intel_dmi_no_dim(const struct dmi_system_id *id)
+{
+   DRM_INFO("No dimming allowed on %s\n", id->ident);
+   return 1;
+}
+
 static const struct intel_dmi_quirk intel_dmi_quirks[] = {
{
.dmi_id_list = &(const struct dmi_system_id[]) {
@@ -136,6 +148,20 @@ static const struct intel_dmi_quirk intel_dmi_quirks[] = {
},
.hook = quirk_no_pps_backlight_power_hook,
},
+   {
+   .dmi_id_list = &(const struct dmi_system_id[]) {
+   {
+   .callback = intel_dmi_no_dim,
+   .ident = "Cybernet T10C Tablet",
+   .matches = {DMI_EXACT_MATCH(DMI_BOARD_VENDOR,
+   "Cybernet 
Manufacturing Inc."),
+   DMI_EXACT_MATCH(DMI_BOARD_NAME, 
"T10C Tablet"),
+   },
+   },
+   { }
+   },
+   .hook = quirk_no_dim,
+   },
 };

 static struct intel_quirk intel_quirks[] = {
@@ -218,6 +244,7 @@ void intel_init_quirks(struct drm_i915_private *i915)
 q->subsystem_device == PCI_ANY_ID))
q->hook(i915);
}
+
for (i = 0; i < ARRAY_SIZE(intel_dmi_quirks); i++) {
if (dmi_check_system(*intel_dmi_quirks[i].dmi_id_list) != 0)
intel_dmi_quirks[i].hook(i915);
diff --git a/drivers/gpu/drm/i915/display/intel_quirks.h 
b/drivers/gpu/drm/i915/display/intel_quirks.h
index 10a4d163149fd..b41c7bbf0a5e3 100644
--- a/drivers/gpu/drm/i915/display/intel_quirks.h
+++ b/drivers/gpu/drm/i915/display/intel_quirks.h
@@ -17,6 +17,7 @@ enum intel_quirk_id {
QUIRK_INVERT_BRIGHTNESS,
QUIRK_LVDS_SSC_DISABLE,
QUIRK_NO_PPS_BACKLIGHT_POWER_HOOK,
+   QUIRK_NO_DIM,
 };

 void intel_init_quirks(struct drm_i915_private *i915);
--
2.41.0.255.g8b1d071c50-goog



[Intel-gfx] [PATCH] drm/i915/quirk: Add quirk for devices that cannot be dimmed

2023-06-29 Thread Allen Ballway
Cybernet T10C cannot be dimmed without the backlight strobing. Create a
new quirk to lock the minimum brightness to the highest supported value.
This aligns the device with its behavior on Windows, which will not
lower the brightness below maximum.

Signed-off-by: Allen Ballway 
---
V2 -> V3: Fix typo.
V1 -> V2: Fix style issue.

.../gpu/drm/i915/display/intel_backlight.c|  5 
 drivers/gpu/drm/i915/display/intel_quirks.c   | 27 +++
 drivers/gpu/drm/i915/display/intel_quirks.h   |  1 +
 3 files changed, 33 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_backlight.c 
b/drivers/gpu/drm/i915/display/intel_backlight.c
index 2e8f17c045222..f015563d3ebd5 100644
--- a/drivers/gpu/drm/i915/display/intel_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_backlight.c
@@ -1192,6 +1192,11 @@ static u32 get_backlight_min_vbt(struct intel_connector 
*connector)

drm_WARN_ON(>drm, panel->backlight.pwm_level_max == 0);

+   if (intel_has_quirk(i915, QUIRK_NO_DIM)) {
+   /* Cannot dim backlight, set minimum to highest value */
+   return panel->backlight.pwm_level_max - 1;
+   }
+
/*
 * XXX: If the vbt value is 255, it makes min equal to max, which leads
 * to problems. There are such machines out there. Either our
diff --git a/drivers/gpu/drm/i915/display/intel_quirks.c 
b/drivers/gpu/drm/i915/display/intel_quirks.c
index a280448df771a..910c95840a539 100644
--- a/drivers/gpu/drm/i915/display/intel_quirks.c
+++ b/drivers/gpu/drm/i915/display/intel_quirks.c
@@ -65,6 +65,12 @@ static void quirk_no_pps_backlight_power_hook(struct 
drm_i915_private *i915)
drm_info(>drm, "Applying no pps backlight power quirk\n");
 }

+static void quirk_no_dim(struct drm_i915_private *i915)
+{
+   intel_set_quirk(i915, QUIRK_NO_DIM);
+   drm_info(>drm, "Applying no dim quirk\n");
+}
+
 struct intel_quirk {
int device;
int subsystem_vendor;
@@ -90,6 +96,12 @@ static int intel_dmi_no_pps_backlight(const struct 
dmi_system_id *id)
return 1;
 }

+static int intel_dmi_no_dim(const struct dmi_system_id *id)
+{
+   DRM_INFO("No dimming allowed on %s\n", id->ident);
+   return 1;
+}
+
 static const struct intel_dmi_quirk intel_dmi_quirks[] = {
{
.dmi_id_list = &(const struct dmi_system_id[]) {
@@ -136,6 +148,20 @@ static const struct intel_dmi_quirk intel_dmi_quirks[] = {
},
.hook = quirk_no_pps_backlight_power_hook,
},
+   {
+   .dmi_id_list = &(const struct dmi_system_id[]) {
+   {
+   .callback = intel_dmi_no_dim,
+   .ident = "Cybernet T10C Tablet",
+   .matches = {DMI_EXACT_MATCH(DMI_BOARD_VENDOR,
+   "Cybernet 
Manufacturing Inc."),
+   DMI_EXACT_MATCH(DMI_BOARD_NAME, 
"T10C Tablet"),
+   },
+   },
+   { }
+   },
+   .hook = quirk_no_dim,
+   },
 };

 static struct intel_quirk intel_quirks[] = {
@@ -218,6 +244,7 @@ void intel_init_quirks(struct drm_i915_private *i915)
 q->subsystem_device == PCI_ANY_ID))
q->hook(i915);
}
+
for (i = 0; i < ARRAY_SIZE(intel_dmi_quirks); i++) {
if (dmi_check_system(*intel_dmi_quirks[i].dmi_id_list) != 0)
intel_dmi_quirks[i].hook(i915);
diff --git a/drivers/gpu/drm/i915/display/intel_quirks.h 
b/drivers/gpu/drm/i915/display/intel_quirks.h
index 10a4d163149fd..b41c7bbf0a5e3 100644
--- a/drivers/gpu/drm/i915/display/intel_quirks.h
+++ b/drivers/gpu/drm/i915/display/intel_quirks.h
@@ -17,6 +17,7 @@ enum intel_quirk_id {
QUIRK_INVERT_BRIGHTNESS,
QUIRK_LVDS_SSC_DISABLE,
QUIRK_NO_PPS_BACKLIGHT_POWER_HOOK,
+   QUIRK_NO_DIM,
 };

 void intel_init_quirks(struct drm_i915_private *i915);
--
2.41.0.255.g8b1d071c50-goog



[Intel-gfx] [PATCH v2] drm/i915/quirk: Add quirk for devices that cannot be dimmed

2023-06-22 Thread Allen Ballway
Cybernet T10C cannot be dimmed without the backlight strobing. Create a
new quirk to lock the minimum brightness to the highest supported value.
This aligns the device with its behavior on Windows, which will not
lower the brightness below maximum.

Signed-off-by: Allen Ballway 
---
V1 -> V2: Fix style issue.

 .../gpu/drm/i915/display/intel_backlight.c|  5 
 drivers/gpu/drm/i915/display/intel_quirks.c   | 27 +++
 drivers/gpu/drm/i915/display/intel_quirks.h   |  1 +
 3 files changed, 33 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_backlight.c 
b/drivers/gpu/drm/i915/display/intel_backlight.c
index 2e8f17c045222..049e95105e8b6 100644
--- a/drivers/gpu/drm/i915/display/intel_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_backlight.c
@@ -1192,6 +1192,11 @@ static u32 get_backlight_min_vbt(struct intel_connector 
*connector)

drm_WARN_ON(>drm, panel->backlight.pwm_level_max == 0);

+   if (intel_has_quirk(i915, QUIRK_NO_DIM)) {
+   /* Cannot dim backlight, set minimum to hightest value */
+   return panel->backlight.pwm_level_max - 1;
+   }
+
/*
 * XXX: If the vbt value is 255, it makes min equal to max, which leads
 * to problems. There are such machines out there. Either our
diff --git a/drivers/gpu/drm/i915/display/intel_quirks.c 
b/drivers/gpu/drm/i915/display/intel_quirks.c
index a280448df771a..910c95840a539 100644
--- a/drivers/gpu/drm/i915/display/intel_quirks.c
+++ b/drivers/gpu/drm/i915/display/intel_quirks.c
@@ -65,6 +65,12 @@ static void quirk_no_pps_backlight_power_hook(struct 
drm_i915_private *i915)
drm_info(>drm, "Applying no pps backlight power quirk\n");
 }

+static void quirk_no_dim(struct drm_i915_private *i915)
+{
+   intel_set_quirk(i915, QUIRK_NO_DIM);
+   drm_info(>drm, "Applying no dim quirk\n");
+}
+
 struct intel_quirk {
int device;
int subsystem_vendor;
@@ -90,6 +96,12 @@ static int intel_dmi_no_pps_backlight(const struct 
dmi_system_id *id)
return 1;
 }

+static int intel_dmi_no_dim(const struct dmi_system_id *id)
+{
+   DRM_INFO("No dimming allowed on %s\n", id->ident);
+   return 1;
+}
+
 static const struct intel_dmi_quirk intel_dmi_quirks[] = {
{
.dmi_id_list = &(const struct dmi_system_id[]) {
@@ -136,6 +148,20 @@ static const struct intel_dmi_quirk intel_dmi_quirks[] = {
},
.hook = quirk_no_pps_backlight_power_hook,
},
+   {
+   .dmi_id_list = &(const struct dmi_system_id[]) {
+   {
+   .callback = intel_dmi_no_dim,
+   .ident = "Cybernet T10C Tablet",
+   .matches = {DMI_EXACT_MATCH(DMI_BOARD_VENDOR,
+   "Cybernet 
Manufacturing Inc."),
+   DMI_EXACT_MATCH(DMI_BOARD_NAME, 
"T10C Tablet"),
+   },
+   },
+   { }
+   },
+   .hook = quirk_no_dim,
+   },
 };

 static struct intel_quirk intel_quirks[] = {
@@ -218,6 +244,7 @@ void intel_init_quirks(struct drm_i915_private *i915)
 q->subsystem_device == PCI_ANY_ID))
q->hook(i915);
}
+
for (i = 0; i < ARRAY_SIZE(intel_dmi_quirks); i++) {
if (dmi_check_system(*intel_dmi_quirks[i].dmi_id_list) != 0)
intel_dmi_quirks[i].hook(i915);
diff --git a/drivers/gpu/drm/i915/display/intel_quirks.h 
b/drivers/gpu/drm/i915/display/intel_quirks.h
index 10a4d163149fd..b41c7bbf0a5e3 100644
--- a/drivers/gpu/drm/i915/display/intel_quirks.h
+++ b/drivers/gpu/drm/i915/display/intel_quirks.h
@@ -17,6 +17,7 @@ enum intel_quirk_id {
QUIRK_INVERT_BRIGHTNESS,
QUIRK_LVDS_SSC_DISABLE,
QUIRK_NO_PPS_BACKLIGHT_POWER_HOOK,
+   QUIRK_NO_DIM,
 };

 void intel_init_quirks(struct drm_i915_private *i915);
--
2.41.0.162.gfafddb0af9-goog



[Intel-gfx] [PATCH] drm/i915/quirk: Add quirk for devices that cannot be dimmed

2023-06-06 Thread Allen Ballway
Cybernet T10C cannot be dimmed without the backlight strobing. Create a
new quirk to lock the minimum brightness to the highest supported value.
This aligns the device with its behavior on Windows, which will not
lower the brightness below maximum.

Signed-off-by: Allen Ballway 
---

 .../gpu/drm/i915/display/intel_backlight.c|  6 +
 drivers/gpu/drm/i915/display/intel_quirks.c   | 27 +++
 drivers/gpu/drm/i915/display/intel_quirks.h   |  1 +
 3 files changed, 34 insertions(+)

diff --git a/drivers/gpu/drm/i915/display/intel_backlight.c 
b/drivers/gpu/drm/i915/display/intel_backlight.c
index 2e8f17c045222..863a33245a3d7 100644
--- a/drivers/gpu/drm/i915/display/intel_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_backlight.c
@@ -1192,6 +1192,11 @@ static u32 get_backlight_min_vbt(struct intel_connector 
*connector)

drm_WARN_ON(>drm, panel->backlight.pwm_level_max == 0);

+   if (intel_has_quirk(i915, QUIRK_NO_DIM)) {
+   /* Cannot dim backlight, set minimum to hightest value */
+   return panel->backlight.pwm_level_max - 1;
+   }
+
/*
 * XXX: If the vbt value is 255, it makes min equal to max, which leads
 * to problems. There are such machines out there. Either our
@@ -1206,6 +1211,7 @@ static u32 get_backlight_min_vbt(struct intel_connector 
*connector)
connector->panel.vbt.backlight.min_brightness, min);
}

+
/* vbt value is a coefficient in range [0..255] */
return scale(min, 0, 255, 0, panel->backlight.pwm_level_max);
 }
diff --git a/drivers/gpu/drm/i915/display/intel_quirks.c 
b/drivers/gpu/drm/i915/display/intel_quirks.c
index a280448df771a..910c95840a539 100644
--- a/drivers/gpu/drm/i915/display/intel_quirks.c
+++ b/drivers/gpu/drm/i915/display/intel_quirks.c
@@ -65,6 +65,12 @@ static void quirk_no_pps_backlight_power_hook(struct 
drm_i915_private *i915)
drm_info(>drm, "Applying no pps backlight power quirk\n");
 }

+static void quirk_no_dim(struct drm_i915_private *i915)
+{
+   intel_set_quirk(i915, QUIRK_NO_DIM);
+   drm_info(>drm, "Applying no dim quirk\n");
+}
+
 struct intel_quirk {
int device;
int subsystem_vendor;
@@ -90,6 +96,12 @@ static int intel_dmi_no_pps_backlight(const struct 
dmi_system_id *id)
return 1;
 }

+static int intel_dmi_no_dim(const struct dmi_system_id *id)
+{
+   DRM_INFO("No dimming allowed on %s\n", id->ident);
+   return 1;
+}
+
 static const struct intel_dmi_quirk intel_dmi_quirks[] = {
{
.dmi_id_list = &(const struct dmi_system_id[]) {
@@ -136,6 +148,20 @@ static const struct intel_dmi_quirk intel_dmi_quirks[] = {
},
.hook = quirk_no_pps_backlight_power_hook,
},
+   {
+   .dmi_id_list = &(const struct dmi_system_id[]) {
+   {
+   .callback = intel_dmi_no_dim,
+   .ident = "Cybernet T10C Tablet",
+   .matches = {DMI_EXACT_MATCH(DMI_BOARD_VENDOR,
+   "Cybernet 
Manufacturing Inc."),
+   DMI_EXACT_MATCH(DMI_BOARD_NAME, 
"T10C Tablet"),
+   },
+   },
+   { }
+   },
+   .hook = quirk_no_dim,
+   },
 };

 static struct intel_quirk intel_quirks[] = {
@@ -218,6 +244,7 @@ void intel_init_quirks(struct drm_i915_private *i915)
 q->subsystem_device == PCI_ANY_ID))
q->hook(i915);
}
+
for (i = 0; i < ARRAY_SIZE(intel_dmi_quirks); i++) {
if (dmi_check_system(*intel_dmi_quirks[i].dmi_id_list) != 0)
intel_dmi_quirks[i].hook(i915);
diff --git a/drivers/gpu/drm/i915/display/intel_quirks.h 
b/drivers/gpu/drm/i915/display/intel_quirks.h
index 10a4d163149fd..b41c7bbf0a5e3 100644
--- a/drivers/gpu/drm/i915/display/intel_quirks.h
+++ b/drivers/gpu/drm/i915/display/intel_quirks.h
@@ -17,6 +17,7 @@ enum intel_quirk_id {
QUIRK_INVERT_BRIGHTNESS,
QUIRK_LVDS_SSC_DISABLE,
QUIRK_NO_PPS_BACKLIGHT_POWER_HOOK,
+   QUIRK_NO_DIM,
 };

 void intel_init_quirks(struct drm_i915_private *i915);
--
2.41.0.162.gfafddb0af9-goog