On Mon, May 4, 2020 at 4:02 AM Andriy Gapon <a...@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 <a...@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
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