linux-kernel - Re: [PATCH v5 2/4] drm/amd/display: Add support for minimum backlight quirk

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Message-ID: <f516b4af-0dac-4607-bdab-e4c83395fe04@t-8ch.de>
Date: Thu, 22 Aug 2024 08:14:08 +0200
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Mario Limonciello <mario.limonciello@....com>
Cc: Alex Deucher <alexander.deucher@....com>, 
	Christian König <christian.koenig@....com>, David Airlie <airlied@...il.com>, 
	Daniel Vetter <daniel@...ll.ch>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
	Harry Wentland <harry.wentland@....com>, Leo Li <sunpeng.li@....com>, 
	Rodrigo Siqueira <Rodrigo.Siqueira@....com>, Matt Hartley <matt.hartley@...il.com>, 
	Kieran Levin <ktl@...mework.net>, Hans de Goede <hdegoede@...hat.com>, 
	Jani Nikula <jani.nikula@...ux.intel.com>, Xinhui Pan <Xinhui.Pan@....com>, 
	Jonathan Corbet <corbet@....net>, amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org, Dustin Howett <dustin@...ett.net>, linux-doc@...r.kernel.org
Subject: Re: [PATCH v5 2/4] drm/amd/display: Add support for minimum
 backlight quirk

On 2024-08-21 15:54:14+0000, Mario Limonciello wrote:
> On 8/18/2024 01:56, Thomas Weißschuh wrote:
> > Not all platforms provide correct PWM backlight capabilities through ATIF.
> 
> I don't think correct is an accurate term here.  How about 'optimial'?

Looks typoed to me :-)

What about this?

Not all platforms provide the full range of PWM backlight capabilities
supported by the hardware through ATIF.


> > Use the generic drm panel minimum backlight quirk infrastructure to
> > override the capabilities where necessary.
> > 
> > Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
> > Tested-by: Dustin L. Howett <dustin@...ett.net>
> 
> The code looks fine to me but please wait for an ack from someone on the AMD
> display team.
> 
> Also, I would like to see comments about the testing with panel power
> savings enabled to avoid a conflict.

Ack.

> 
> Reviewed-by: Mario Limonciello <mario.limonciello@....com>
> > ---
> >   drivers/gpu/drm/amd/amdgpu/Kconfig                |  1 +
> >   drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 10 ++++++++++
> >   2 files changed, 11 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/amd/amdgpu/Kconfig b/drivers/gpu/drm/amd/amdgpu/Kconfig
> > index 0051fb1b437f..655c10aef2e3 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/Kconfig
> > +++ b/drivers/gpu/drm/amd/amdgpu/Kconfig
> > @@ -23,6 +23,7 @@ config DRM_AMDGPU
> >   	select DRM_BUDDY
> >   	select DRM_SUBALLOC_HELPER
> >   	select DRM_EXEC
> > +	select DRM_PANEL_BACKLIGHT_QUIRKS
> >   	# amdgpu depends on ACPI_VIDEO when ACPI is enabled, for select to work
> >   	# ACPI_VIDEO's dependencies must also be selected.
> >   	select INPUT if ACPI
> > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > index 983a977632ff..056960ea335c 100644
> > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > @@ -93,6 +93,7 @@
> >   #include <drm/drm_fourcc.h>
> >   #include <drm/drm_edid.h>
> >   #include <drm/drm_eld.h>
> > +#include <drm/drm_utils.h>
> >   #include <drm/drm_vblank.h>
> >   #include <drm/drm_audio_component.h>
> >   #include <drm/drm_gem_atomic_helper.h>
> > @@ -3333,6 +3334,8 @@ static void update_connector_ext_caps(struct amdgpu_dm_connector *aconnector)
> >   	struct drm_connector *conn_base;
> >   	struct amdgpu_device *adev;
> >   	struct drm_luminance_range_info *luminance_range;
> > +	const struct drm_edid *drm_edid;
> > +	int min_input_signal_override;
> >   	if (aconnector->bl_idx == -1 ||
> >   	    aconnector->dc_link->connector_signal != SIGNAL_TYPE_EDP)
> > @@ -3367,6 +3370,13 @@ static void update_connector_ext_caps(struct amdgpu_dm_connector *aconnector)
> >   		caps->aux_min_input_signal = 0;
> >   		caps->aux_max_input_signal = 512;
> >   	}
> > +
> > +	drm_edid = drm_edid_alloc(aconnector->edid,
> > +				  EDID_LENGTH * (aconnector->edid->extensions + 1));
> > +	min_input_signal_override = drm_get_panel_min_brightness_quirk(drm_edid);
> > +	drm_edid_free(drm_edid);
> > +	if (min_input_signal_override >= 0)
> > +		caps->min_input_signal = min_input_signal_override;
> >   }
> >   void amdgpu_dm_update_connector_after_detect(
> > 
>