The Thundersoft TST178 tablet uses a DSI panel with an external PWM
controller (as all DSI panels do). But unlike other DSI panels a duty-cycle
of 100% turns the backlight off and 0% sets it to maximum brightness.
I've checked the VBT and there is a BDB_LVDS_BACKLIGHT section, but
it does not set the active_low_pwm flag. This tablet re-uses the main
PCI vendor and product ids for the subsystem ids, so I see no other option
then to add a DMI based quirk to fix this.
Note that the PWM backlight code in intel_panel.c currently does not honor
the vbt.active_low_pwm flag, but that does not matter in this case.
Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
---
drivers/gpu/drm/i915/display/intel_quirks.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/drivers/gpu/drm/i915/display/intel_quirks.c b/drivers/gpu/drm/i915/display/intel_quirks.c
index 399b1542509f..54dba152ead8 100644
--- a/drivers/gpu/drm/i915/display/intel_quirks.c
+++ b/drivers/gpu/drm/i915/display/intel_quirks.c
@@ -82,6 +82,16 @@ static const struct intel_dmi_quirk intel_dmi_quirks[] = {
DMI_MATCH(DMI_PRODUCT_NAME, ""),
},
},
+ {
+ .callback = intel_dmi_reverse_brightness,
+ .ident = "Thundersoft TST178 tablet",
+ /* DMI strings are too generic, also match on BIOS date */
+ .matches = {DMI_EXACT_MATCH(DMI_BOARD_VENDOR, "AMI Corporation"),
+ DMI_EXACT_MATCH(DMI_BOARD_NAME, "Aptio CRB"),
+ DMI_EXACT_MATCH(DMI_PRODUCT_NAME, "To be filled by O.E.M."),
+ DMI_EXACT_MATCH(DMI_BIOS_DATE, "04/15/2014"),
+ },
+ },
{ } /* terminating entry */
},
.hook = quirk_invert_brightness,
--
2.25.0
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