Hi Allen,
On Tue, Oct 17, 2023 at 06:01:39PM +0000, Allen Ballway wrote:
> 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);
I think it would be better if we did:
if (!intel_has_quirk(i915, QUIRK_IGNORE_DEFAULT_PWM_FREQUENCY)) {
ctl = intel_de_read(i915, VLV_BLC_PWM_CTL(pipe));
panel->backlight.pwm_level_max = ctl >> 16;
} else {
panel->backlight.pwm_level_max = 0;
}
if (!panel->backlight.pwm_level_max)
panel->backlight.pwm_level_max =
get_backlight_max_vbt(connector);
The "else" branch can potentially be omitted if we know that backlight
member is initialized to 0 (I suspect it is).
>
> 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
You want a trailing comma here.
> };
>
> void intel_init_quirks(struct drm_i915_private *i915);
> --
> 2.42.0.655.g421f12c284-goog
>
Thanks.
--
Dmitry
