[resend,2/2] drm/i915: Add invert-brightness quirk for Thundersoft TST178 tablet
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Message ID 20200221172927.510027-2-hdegoede@redhat.com
State New
Headers show
  • [resend,1/2] drm/i915: panel: Use intel_panel_compute_brightness() from pwm_setup_backlight()
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Commit Message

Hans de Goede Feb. 21, 2020, 5:29 p.m. UTC
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>
 drivers/gpu/drm/i915/display/intel_quirks.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff mbox series

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[] = {
+			{
+				.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_PRODUCT_NAME, "To be filled by O.E.M."),
+					    DMI_EXACT_MATCH(DMI_BIOS_DATE, "04/15/2014"),
+				},
+			},
 			{ }  /* terminating entry */
 		.hook = quirk_invert_brightness,