Commit 8f1e5740 authored Feb 21, 2020 by Hans de Goede

drm/i915: Add invert-brightness quirk for Thundersoft TST178 tablet

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@redhat.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200221172927.510027-2-hdegoede@redhat.com

parent d59b1d1b

drivers/gpu/drm/i915/display/intel_quirks.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -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,

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