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

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Message-ID: <20231017175728.1.Ibc6408a8ff1f334974104c5bcc25f2f35a57f36e@changeid>
Date:   Tue, 17 Oct 2023 18:01:39 +0000
From:   Allen Ballway <ballway@...omium.org>
To:     dri-devel@...ts.freedesktop.org
Cc:     arun.r.murthy@...el.com, intel-gfx@...ts.freedesktop.org,
        jani.nikula@...ux.intel.com, linux-kernel@...r.kernel.org,
        Allen Ballway <ballway@...omium.org>
Subject: [PATCH] drm/i915/quirk: Add quirk for devices with incorrect PWM frequency

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 <ballway@...omium.org>

---

 .../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(&i915->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(&i915->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