Re: [PATCH v3 RESEND] drm/i915/quirk: Add quirk for devices that cannot be dimmed

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 08 Aug 2023, Allen Ballway <ballway@chromium.org> wrote:
> Cybernet T10C cannot be dimmed without the backlight strobing. Create a
> new quirk to lock the minimum brightness to the highest supported value.
> This aligns the device with its behavior on Windows, which will not
> lower the brightness below maximum.

Noting here for the benefit of others, it's possible to make the
brightness work [1], now we "just" need to figure out how to do that
nicely. So we should drop this patch.

BR,
Jani.


[1] https://gitlab.freedesktop.org/drm/intel/-/issues/8187#note_2072633

>
> Signed-off-by: Allen Ballway <ballway@chromium.org>
> ---
> V2 -> V3: Fix typo.
> V1 -> V2: Fix style issue.
>
> .../gpu/drm/i915/display/intel_backlight.c    |  5 ++++
>  drivers/gpu/drm/i915/display/intel_quirks.c   | 27 +++++++++++++++++++
>  drivers/gpu/drm/i915/display/intel_quirks.h   |  1 +
>  3 files changed, 33 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_backlight.c b/drivers/gpu/drm/i915/display/intel_backlight.c
> index 2e8f17c045222..f015563d3ebd5 100644
> --- a/drivers/gpu/drm/i915/display/intel_backlight.c
> +++ b/drivers/gpu/drm/i915/display/intel_backlight.c
> @@ -1192,6 +1192,11 @@ static u32 get_backlight_min_vbt(struct intel_connector *connector)
>
>  	drm_WARN_ON(&i915->drm, panel->backlight.pwm_level_max == 0);
>
> +	if (intel_has_quirk(i915, QUIRK_NO_DIM)) {
> +		/* Cannot dim backlight, set minimum to highest value */
> +		return panel->backlight.pwm_level_max - 1;
> +	}
> +
>  	/*
>  	 * XXX: If the vbt value is 255, it makes min equal to max, which leads
>  	 * to problems. There are such machines out there. Either our
> diff --git a/drivers/gpu/drm/i915/display/intel_quirks.c b/drivers/gpu/drm/i915/display/intel_quirks.c
> index a280448df771a..910c95840a539 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_no_dim(struct drm_i915_private *i915)
> +{
> +	intel_set_quirk(i915, QUIRK_NO_DIM);
> +	drm_info(&i915->drm, "Applying no dim quirk\n");
> +}
> +
>  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_no_dim(const struct dmi_system_id *id)
> +{
> +	DRM_INFO("No dimming allowed 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_no_dim,
> +				.ident = "Cybernet T10C Tablet",
> +				.matches = {DMI_EXACT_MATCH(DMI_BOARD_VENDOR,
> +							    "Cybernet Manufacturing Inc."),
> +					    DMI_EXACT_MATCH(DMI_BOARD_NAME, "T10C Tablet"),
> +				},
> +			},
> +			{ }
> +		},
> +		.hook = quirk_no_dim,
> +	},
>  };
>
>  static struct intel_quirk intel_quirks[] = {
> @@ -218,6 +244,7 @@ void intel_init_quirks(struct drm_i915_private *i915)
>  		     q->subsystem_device == PCI_ANY_ID))
>  			q->hook(i915);
>  	}
> +
>  	for (i = 0; i < ARRAY_SIZE(intel_dmi_quirks); i++) {
>  		if (dmi_check_system(*intel_dmi_quirks[i].dmi_id_list) != 0)
>  			intel_dmi_quirks[i].hook(i915);
> diff --git a/drivers/gpu/drm/i915/display/intel_quirks.h b/drivers/gpu/drm/i915/display/intel_quirks.h
> index 10a4d163149fd..b41c7bbf0a5e3 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_NO_DIM,
>  };
>
>  void intel_init_quirks(struct drm_i915_private *i915);
> --
> 2.41.0.255.g8b1d071c50-goog
>

-- 
Jani Nikula, Intel Open Source Graphics Center