Re: [PATCH] drm: panel-backlight-quirks: Add ASUS ROG Flow X13 3840x2400 panel

[Mario Limonciello <superm1@kernel.org>]

On 10/31/26 08:45, Hugo Sales wrote:
> On an ASUS ROG Flow X13 GV301QH (BIOS 418) ATIF
> QUERY_BACKLIGHT_TRANSFER_CHARACTERISTICS answers with a minimum input
> signal of 12 and 49 curve points for the Sharp LQ134R1JW51 panel, and
> amdgpu logs "Using custom brightness curve". With that minimum,
> brightness 0 gives 4.7% duty
> 
> With the quirk, brightness 0 sends PWM 0 (read back from
> amdgpu_current_backlight_pwm in debugfs). The panel stays lit, but much
> dimmer than the old 4.7% floor. Its LED driver has a minimum of its own,
> so 0 does not turn the backlight off
> 
> linux-hardware.org also lists this panel in a GV301QE. Match the ASUS
> vendor and the panel, as the Framework 13 entries do, and let the
> brightness reach the bottom of the PWM range
> 
> Signed-off-by: Hugo Sales <hugo@hsal.es>
> ---
> I could only test this on a GV301QH. The entry matches any ASUS laptop
> with this panel, and linux-hardware.org only lists it in ROG Flow X13s,
> one of them a GV301QE. If you'd rather limit it to the GV301QH, I can
> add a DMI_BOARD_NAME match in v2
> 
>   drivers/gpu/drm/drm_panel_backlight_quirks.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_panel_backlight_quirks.c b/drivers/gpu/drm/drm_panel_backlight_quirks.c
> index 2d0238382ebd5..b60333e748741 100644
> --- a/drivers/gpu/drm/drm_panel_backlight_quirks.c
> +++ b/drivers/gpu/drm/drm_panel_backlight_quirks.c
> @@ -69,6 +69,14 @@ static const struct drm_get_panel_backlight_quirk drm_panel_min_backlight_quirks
>   		.dmi_match_other.value = "Galileo",
>   		.quirk = { .min_brightness = 1, },
>   	},
> +	/* ASUS ROG Flow X13 3840x2400 panel */
> +	{
> +		.dmi_match.field = DMI_SYS_VENDOR,
> +		.dmi_match.value = "ASUSTeK COMPUTER INC.",
> +		.ident.panel_id = drm_edid_encode_panel_id('S', 'H', 'P', 0x151b),
> +		.ident.name = "LQ134R1JW51",
> +		.quirk = { .min_brightness = 1, },
> +	},
>   	/* Have OLED Panels with brightness issue when last byte is 0/1 */
>   	{
>   		.dmi_match.field = DMI_SYS_VENDOR,


Was this from looking at a datasheet or from empirical measurements? 
The reason it was safe to do on the Framework panel was because there 
was a confirmation the datasheet allowed a lower value.

We don't want to be damaging hardware running it outside of spec.