Re: [PATCH v4 11/31] drm/i915: Call acpi_video_register_backlight() (v2)

[Jani Nikula <jani.nikula@linux.intel.com>]

On Wed, 24 Aug 2022, Hans de Goede <hdegoede@redhat.com> wrote:
> Hi,
>
> On 8/24/22 14:47, Jani Nikula wrote:
>> On Wed, 24 Aug 2022, Hans de Goede <hdegoede@redhat.com> wrote:
>>> On machins without an i915 opregion the acpi_video driver immediately
>>> probes the ACPI video bus and used to also immediately register
>>> acpi_video# backlight devices when supported.
>>>
>>> Once the drm/kms driver then loaded later and possibly registered
>>> a native backlight device then the drivers/acpi/video_detect.c code
>>> unregistered the acpi_video0 device to avoid there being 2 backlight
>>> devices (when acpi_video_get_backlight_type()==native).
>>>
>>> This means that userspace used to briefly see 2 devices and the
>>> disappearing of acpi_video0 after a brief time confuses the systemd
>>> backlight level save/restore code, see e.g.:
>>> https://bbs.archlinux.org/viewtopic.php?id=269920
>>>
>>> To fix this the ACPI video code has been modified to make backlight class
>>> device registration a separate step, relying on the drm/kms driver to
>>> ask for the acpi_video backlight registration after it is done setting up
>>> its native backlight device.
>>>
>>> Add a call to the new acpi_video_register_backlight() after the i915 calls
>>> acpi_video_register() (after setting up the i915 opregion) so that the
>>> acpi_video backlight devices get registered on systems where the i915
>>> native backlight device is not registered.
>>>
>>> Changes in v2:
>>> -Only call acpi_video_register_backlight() when a panel is detected
>>>
>>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>>> ---
>>>  drivers/gpu/drm/i915/display/intel_display.c | 8 ++++++++
>>>  drivers/gpu/drm/i915/display/intel_panel.c   | 3 +++
>>>  drivers/gpu/drm/i915/i915_drv.h              | 2 ++
>>>  3 files changed, 13 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
>>> index 6103b02c081f..2bb53efdb149 100644
>>> --- a/drivers/gpu/drm/i915/display/intel_display.c
>>> +++ b/drivers/gpu/drm/i915/display/intel_display.c
>>> @@ -9088,6 +9088,14 @@ void intel_display_driver_register(struct drm_i915_private *i915)
>>>  	/* Must be done after probing outputs */
>>>  	intel_opregion_register(i915);
>>>  	acpi_video_register();
>>> +	/*
>>> +	 * Only call this if i915 is driving the internal panel. If the internal
>>> +	 * panel is not driven by i915 then another GPU driver may still register
>>> +	 * a native backlight driver later and this should only be called after
>>> +	 * any native backlights have been registered.
>>> +	 */
>>> +	if (i915->have_panel)
>>> +		acpi_video_register_backlight();
>> 
>> Apologies for procrastinating the review.
>> 
>> Please let's not add new flags like have_panel to i915; we're trying to
>> clean it up instead.
>> 
>> The code here needs to iterate over the connectors to decide. Maybe
>> better abstracted a function.
>
> So something like add a i915_have_panel() helper which iterates over all
> the connectors and then of 1 of them is of the LVDS / eDP / DSI type
> return true ?

Or abstract the acpi_video_register_backlight() calling in a function
that does the loop and calls if necessary.

BR,
Jani.


>
> Regards,
>
> Hans
>
>
>
>>>  	intel_audio_init(i915);
>>>  
>>> diff --git a/drivers/gpu/drm/i915/display/intel_panel.c b/drivers/gpu/drm/i915/display/intel_panel.c
>>> index 237a40623dd7..4536c527f50c 100644
>>> --- a/drivers/gpu/drm/i915/display/intel_panel.c
>>> +++ b/drivers/gpu/drm/i915/display/intel_panel.c
>>> @@ -646,8 +646,11 @@ intel_panel_mode_valid(struct intel_connector *connector,
>>>  
>>>  int intel_panel_init(struct intel_connector *connector)
>>>  {
>>> +	struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
>>>  	struct intel_panel *panel = &connector->panel;
>>>  
>>> +	dev_priv->have_panel = true;
>>> +
>>>  	intel_backlight_init_funcs(panel);
>>>  
>>>  	drm_dbg_kms(connector->base.dev,
>>> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
>>> index 69ce6db6a7c1..14b0dcaf25c2 100644
>>> --- a/drivers/gpu/drm/i915/i915_drv.h
>>> +++ b/drivers/gpu/drm/i915/i915_drv.h
>>> @@ -756,6 +756,8 @@ struct drm_i915_private {
>>>  
>>>  	bool ipc_enabled;
>>>  
>>> +	bool have_panel;
>>> +
>>>  	struct intel_audio_private audio;
>>>  
>>>  	struct i915_pmu pmu;
>> 
>

-- 
Jani Nikula, Intel Open Source Graphics Center