linux-kernel - Re: [PATCH 1/1] drm/amd/display: Add quirk to force backlight type on some TUXEDO devices

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Message-ID: <dnu7mbrw7fs4qvwi2alvgrqvonsrucrq7hgxgkqyyqn5djzkkj@c7grkpftjbw4>
Date: Mon, 23 Jun 2025 13:13:43 -0600
From: Rodrigo Siqueira <siqueira@...lia.com>
To: Werner Sembach <wse@...edocomputers.com>
Cc: harry.wentland@....com, sunpeng.li@....com, alexander.deucher@....com, 
	christian.koenig@....com, airlied@...il.com, simona@...ll.ch, 
	amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
	Alex Hung <alex.hung@....com>, Daniel Wheeler <daniel.wheeler@....com>, 
	Mario Limonciello <mario.limonciello@....com>
Subject: Re: [PATCH 1/1] drm/amd/display: Add quirk to force backlight type
 on some TUXEDO devices

On 06/23, Werner Sembach wrote:
> gentle bump
> 
> Am 09.04.25 um 18:27 schrieb Werner Sembach:
> > The display backlight on TUXEDO Polaris AMD Gen2 and Gen3 with panels
> > BOE 2420 and BOE 2423 must be forced to pwn controlled to be able to
> > control the brightness.
> > 
> > This could already be archived via a module parameter, but this patch adds
> > a quirk to apply this by default on the mentioned device + panel
> > combinations.
> > 
> > Signed-off-by: Werner Sembach <wse@...edocomputers.com>
> > Cc: stable@...r.kernel.org
> > ---
> >   .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 32 ++++++++++++++++++-
> >   1 file changed, 31 insertions(+), 1 deletion(-)
> > 
> > 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 39df45f652b32..2bad6274ad8ff 100644
> > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > @@ -1625,11 +1625,13 @@ static bool dm_should_disable_stutter(struct pci_dev *pdev)
> >   struct amdgpu_dm_quirks {
> >   	bool aux_hpd_discon;
> >   	bool support_edp0_on_dp1;
> > +	bool boe_2420_2423_bl_force_pwm;
> >   };
> >   static struct amdgpu_dm_quirks quirk_entries = {
> >   	.aux_hpd_discon = false,
> > -	.support_edp0_on_dp1 = false
> > +	.support_edp0_on_dp1 = false,
> > +	.boe_2420_2423_bl_force_pwm = false
> >   };
> >   static int edp0_on_dp1_callback(const struct dmi_system_id *id)
> > @@ -1644,6 +1646,12 @@ static int aux_hpd_discon_callback(const struct dmi_system_id *id)
> >   	return 0;
> >   }
> > +static int boe_2420_2423_bl_force_pwm_callback(const struct dmi_system_id *id)
> > +{
> > +	quirk_entries.boe_2420_2423_bl_force_pwm = true;
> > +	return 0;
> > +}
> > +
> >   static const struct dmi_system_id dmi_quirk_table[] = {
> >   	{
> >   		.callback = aux_hpd_discon_callback,
> > @@ -1722,6 +1730,20 @@ static const struct dmi_system_id dmi_quirk_table[] = {
> >   			DMI_MATCH(DMI_PRODUCT_NAME, "HP EliteBook 665 16 inch G11 Notebook PC"),
> >   		},
> >   	},
> > +	{
> > +		// TUXEDO Polaris AMD Gen2
> > +		.callback = boe_2420_2423_bl_force_pwm_callback,
> > +		.matches = {
> > +			DMI_MATCH(DMI_BOARD_NAME, "GMxNGxx"),
> > +		},
> > +	},
> > +	{
> > +		// TUXEDO Polaris AMD Gen3
> > +		.callback = boe_2420_2423_bl_force_pwm_callback,
> > +		.matches = {
> > +			DMI_MATCH(DMI_BOARD_NAME, "GMxZGxx"),
> > +		},
> > +	},
> >   	{}
> >   	/* TODO: refactor this from a fixed table to a dynamic option */
> >   };
> > @@ -3586,6 +3608,7 @@ static void update_connector_ext_caps(struct amdgpu_dm_connector *aconnector)
> >   	struct amdgpu_device *adev;
> >   	struct drm_luminance_range_info *luminance_range;
> >   	int min_input_signal_override;
> > +	u32 panel;
> >   	if (aconnector->bl_idx == -1 ||
> >   	    aconnector->dc_link->connector_signal != SIGNAL_TYPE_EDP)
> > @@ -3610,6 +3633,13 @@ static void update_connector_ext_caps(struct amdgpu_dm_connector *aconnector)
> >   		caps->aux_support = false;
> >   	else if (amdgpu_backlight == 1)
> >   		caps->aux_support = true;
> > +	else if (amdgpu_backlight == -1 &&
> > +		 quirk_entries.boe_2420_2423_bl_force_pwm) {
> > +		panel = drm_edid_get_panel_id(aconnector->drm_edid);
> > +		if (panel == drm_edid_encode_panel_id('B', 'O', 'E', 0x0974) ||
> > +		    panel == drm_edid_encode_panel_id('B', 'O', 'E', 0x0977))
> > +			caps->aux_support = false;
> > +	}

It lgtm,

Additionally, I believe this is safe to merge since it only affects a
specific device. Perhaps display folks would like to include this as
part of this week's promotion? Anyway, Cc other devs from the display.

Reviewed-by: Rodrigo Siqueira <siqueira@...lia.com>

> >   	if (caps->aux_support)
> >   		aconnector->dc_link->backlight_control_type = BACKLIGHT_CONTROL_AMD_AUX;

-- 
Rodrigo Siqueira