linux-kernel - [PATCH v2] drm/i915/display: Add quirk to force backlight type on some TUXEDO devices

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Message-ID: <20260121223944.1104951-1-wse@tuxedocomputers.com>
Date: Wed, 21 Jan 2026 23:38:55 +0100
From: Werner Sembach <wse@...edocomputers.com>
To: Jani Nikula <jani.nikula@...ux.intel.com>,
	Rodrigo Vivi <rodrigo.vivi@...el.com>,
	Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
	Tvrtko Ursulin <tursulin@...ulin.net>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>
Cc: Werner Sembach <wse@...edocomputers.com>,
	intel-gfx@...ts.freedesktop.org,
	intel-xe@...ts.freedesktop.org,
	dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2] drm/i915/display: Add quirk to force backlight type on some TUXEDO devices

The display backlight on TUXEDO DX1708 and InsanityBook 15 v1 with panels
AUO 12701 and AUO 12701 must be forced to INTEL_DP_AUX_BACKLIGHT_ON to be
able to control the brightness.

This could already be archived via a module parameter, but this patch adds
a quirk to apply this by default on the mentioned devices.

This patch does not actually test for the exact panels as the id that is
used in the intel_dpcd_quirks list is sadly zeroed on the devices, but
afaik all these devices use try_intel_interface first anyway so all the
quirk does is to add the fallback to try_vesa_interface, so the behaviour
on the devices not needing the quirk and fallback should functionally stay
the same.

Cc: stable@...r.kernel.org
Signed-off-by: Werner Sembach <wse@...edocomputers.com>
---
 .../drm/i915/display/intel_dp_aux_backlight.c |  9 ++++++-
 drivers/gpu/drm/i915/display/intel_quirks.c   | 25 ++++++++++++++++++-
 drivers/gpu/drm/i915/display/intel_quirks.h   |  1 +
 3 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
index 0a3a3f6a5f9d8..bbdfa142d084d 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux_backlight.c
@@ -41,6 +41,7 @@
 #include "intel_display_types.h"
 #include "intel_dp.h"
 #include "intel_dp_aux_backlight.h"
+#include "intel_quirks.h"
 
 /*
  * DP AUX registers for Intel's proprietary HDR backlight interface. We define
@@ -661,11 +662,17 @@ int intel_dp_aux_init_backlight_funcs(struct intel_connector *connector)
 	struct drm_device *dev = connector->base.dev;
 	struct intel_panel *panel = &connector->panel;
 	bool try_intel_interface = false, try_vesa_interface = false;
+	int enable_dpcd_backlight;
 
 	/* Check the VBT and user's module parameters to figure out which
 	 * interfaces to probe
 	 */
-	switch (display->params.enable_dpcd_backlight) {
+	enable_dpcd_backlight = display->params.enable_dpcd_backlight;
+	if (enable_dpcd_backlight == INTEL_DP_AUX_BACKLIGHT_AUTO &&
+	    intel_has_dpcd_quirk(intel_dp, QUIRK_ENABLE_DPCD_BACKLIGHT))
+		enable_dpcd_backlight = INTEL_DP_AUX_BACKLIGHT_ON;
+
+	switch (enable_dpcd_backlight) {
 	case INTEL_DP_AUX_BACKLIGHT_OFF:
 		return -ENODEV;
 	case INTEL_DP_AUX_BACKLIGHT_AUTO:
diff --git a/drivers/gpu/drm/i915/display/intel_quirks.c b/drivers/gpu/drm/i915/display/intel_quirks.c
index d2e16b79d6be1..df20930f73f75 100644
--- a/drivers/gpu/drm/i915/display/intel_quirks.c
+++ b/drivers/gpu/drm/i915/display/intel_quirks.c
@@ -86,6 +86,14 @@ static void quirk_edp_limit_rate_hbr2(struct intel_display *display)
 	drm_info(display->drm, "Applying eDP Limit rate to HBR2 quirk\n");
 }
 
+static void quirk_enable_dpcd_backlight(struct intel_dp *intel_dp)
+{
+	struct intel_display *display = to_intel_display(intel_dp);
+
+	intel_set_dpcd_quirk(intel_dp, QUIRK_ENABLE_DPCD_BACKLIGHT);
+	drm_info(display->drm, "Applying Enable DPCD Backlight quirk\n");
+}
+
 struct intel_quirk {
 	int device;
 	int subsystem_vendor;
@@ -251,7 +259,22 @@ static const struct intel_dpcd_quirk intel_dpcd_quirks[] = {
 		.sink_oui = SINK_OUI(0x38, 0xec, 0x11),
 		.hook = quirk_fw_sync_len,
 	},
-
+	/* TUXEDO InsanityBook 15 v1 */
+	{
+		.device = 0x591b,
+		.subsystem_vendor = 0x1558,
+		.subsystem_device = 0x9501,
+		.sink_oui = SINK_OUI(0x38, 0xec, 0x11),
+		.hook = quirk_enable_dpcd_backlight,
+	},
+	/* TUXEDO DX1708 */
+	{
+		.device = 0x3e9b,
+		.subsystem_vendor = 0x1558,
+		.subsystem_device = 0x8500,
+		.sink_oui = SINK_OUI(0x38, 0xec, 0x11),
+		.hook = quirk_enable_dpcd_backlight,
+	},
 };
 
 void intel_init_quirks(struct intel_display *display)
diff --git a/drivers/gpu/drm/i915/display/intel_quirks.h b/drivers/gpu/drm/i915/display/intel_quirks.h
index 06da0e286c67c..686f306ab4472 100644
--- a/drivers/gpu/drm/i915/display/intel_quirks.h
+++ b/drivers/gpu/drm/i915/display/intel_quirks.h
@@ -21,6 +21,7 @@ enum intel_quirk_id {
 	QUIRK_NO_PPS_BACKLIGHT_POWER_HOOK,
 	QUIRK_FW_SYNC_LEN,
 	QUIRK_EDP_LIMIT_RATE_HBR2,
+	QUIRK_ENABLE_DPCD_BACKLIGHT,
 };
 
 void intel_init_quirks(struct intel_display *display);
-- 
2.43.0