linux-kernel - Re: Backlight control broken on UM325 (OLED) on 5.15 (bisected)

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Date:   Tue, 16 Nov 2021 14:32:59 +0100
From:   Samuel Čavoj <samuel@...oj.net>
To:     Alex Deucher <alexdeucher@...il.com>
Cc:     Alex Deucher <alexander.deucher@....com>,
        Leo Li <sunpeng.li@....com>, Roman Li <Roman.Li@....com>,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>
Subject: Re: Backlight control broken on UM325 (OLED) on 5.15 (bisected)

Hi Alex,

thank you for your response.

On 15.11.2021 10:43, Alex Deucher wrote:
> [...]
>
> That patch adds support for systems with multiple backlights.  Do you
> have multiple backlight devices now?  If so, does the other one work?

No, there is still only one backlight device -- amdgpu_bl0.
> 
> Can you also try this patch?
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> index 4811b0faafd9..67163c9d49e6 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> @@ -854,8 +854,8 @@ int amdgpu_acpi_init(struct amdgpu_device *adev)
>                 if (amdgpu_device_has_dc_support(adev)) {
>  #if defined(CONFIG_DRM_AMD_DC)
>                         struct amdgpu_display_manager *dm = &adev->dm;
> -                       if (dm->backlight_dev[0])
> -                               atif->bd = dm->backlight_dev[0];
> +                       if (dm->backlight_dev[1])
> +                               atif->bd = dm->backlight_dev[1];
>  #endif
>                 } else {
>                         struct drm_encoder *tmp;
> 

There is no difference in behaviour after applying the patch.

Samuel

> 
> Alex
> 
> >
> > Regards,
> > Samuel Čavoj
> >
> > [0]: https://www.reddit.com/r/AMDLaptops/comments/qst0fm/after_updating_to_linux_515_my_brightness/