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

[Allen Ballway]

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 <ball...@chromium.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