amdgpu, dc, backlight brightness

[Alex Deucher]

On Mon, May 4, 2020 at 4:02 AM Andriy Gapon <avg at freebsd.org> wrote:
>
> On 29/04/2020 21:15, Alex Deucher wrote:
> > I think it varies from OEM to OEM and whatever windows required at the
> > time.  The sbios may also do different things depending on the osi
> > string passed to ACPI.  Originally, ACPI handled it all directly.
> > Then we got some laptops which which did the whole event via ATIF
> > thing (even that I think varied based on the .  Later, I think the
> > keys just produced brightness events and it was up to the OS to do
> > something with them so the user's environment would catch the events
> > and adjust the backlight via the standard OS backlight control
> > interface.  We never hooked up the ATIF stuff to DC since I don't
> > recall ever running into any laptops that used it for backlight
> > control (the code was carried over from radeon when we forked amdgpu).
>
> Thank you for the information!
> Indeed, I see that there are so many quirks in how brightness keys are handled
> by firmware.  Ranging from actually changing the brightness to posting ACPI
> events to posting key codes.  And then those options are not exclusive of each
> other.
>
> Just in case, I've written a bit of code for ATIF handler to control the
> backlight in the DC case.  I doubt that it is very useful, it was mostly an
> exercise for myself.
>

Care to send it out as a proper patch?  I don't mind applying it on
the off chance there are some laptops out there that might use this
path.

Alex

> ----------------------------------------------------------------------------
> commit ed2ca1d7e3fbdb641d9a1bc2de9b88e2927ff1bd
> Author: Andriy Gapon <avg at FreeBSD.org>
> Date:   Thu Apr 30 14:47:11 2020 +0300
>
>     amdgpu_acpi: perform automatic backlight adjustment in the DC case too
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> index 04bbd8f41441c..62fbae1177091 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> @@ -444,7 +444,6 @@ static int amdgpu_atif_handler(struct amdgpu_device *adev,
>
>                 DRM_DEBUG_DRIVER("ATIF: %d pending SBIOS requests\n", count);
>
> -               /* todo: add DC handling */
>                 if ((req.pending & ATIF_PANEL_BRIGHTNESS_CHANGE_REQUEST) &&
>                     !amdgpu_device_has_dc_support(adev)) {
>                         struct amdgpu_encoder *enc = atif->encoder_for_bl;
> @@ -463,6 +462,34 @@ static int amdgpu_atif_handler(struct amdgpu_device *adev,
>  #endif
>                         }
>                 }
> +#if defined(CONFIG_BACKLIGHT_CLASS_DEVICE) ||
> defined(CONFIG_BACKLIGHT_CLASS_DEVICE_MODULE)
> +               if ((req.pending & ATIF_PANEL_BRIGHTNESS_CHANGE_REQUEST) &&
> +                   amdgpu_device_has_dc_support(adev)) {
> +                       struct amdgpu_display_manager *dm = &adev->dm;
> +                       struct backlight_device *bd = dm->backlight_dev;
> +
> +                       if (bd) {
> +                               DRM_DEBUG_DRIVER("Changing brightness to %d\n",
> +                                                req.backlight_level);
> +
> +                               /*
> +                                * Newer Linux has
> +                                * backlight_device_set_brightness, but it is
> +                                * hardwired to post BACKLIGHT_UPDATE_SYSFS.
> +                                */
> +                               mutex_lock(&bd->ops_lock);
> +                               if (bd->ops &&
> +                                   req.backlight_level <= bd->props.max_brightness) {
> +                                       bd->props.brightness = req.backlight_level;
> +                                       backlight_update_status(bd);
> +                               }
> +                               mutex_unlock(&bd->ops_lock);
> +#if 0
> +                               backlight_generate_event(bd, BACKLIGHT_UPDATE_HOTKEY);
> +#endif
> +                       }
> +               }
> +#endif
>                 if (req.pending & ATIF_DGPU_DISPLAY_EVENT) {
>                         if ((adev->flags & AMD_IS_PX) &&
>                             amdgpu_atpx_dgpu_req_power_for_displays()) {
>
>
>
> --
> Andriy Gapon