Hi,
On 10/31/22 23:09, Daniel Dadap wrote:
> Thanks, Hans:
>
> On Mon, Oct 31, 2022 at 10:25:56PM +0100, Hans de Goede wrote:
>> The Dell G15 5515 has the WMI interface (and WMI call returns) expected
>> by the nvidia-wmi-ec-backlight interface. But the backlight class device
>> registered by the nvidia-wmi-ec-backlight driver does not actually work.
>>
>> The amdgpu_bl0 native GPU backlight class device does actually work,
>> add a backlight=native DMI quirk for this.
>
> I'm not certain whether you have direct access to the system, but I am
> curious as to what mode the system is in when it exposes a non-working
> WMI backlight interface. The expectation is that the WMI EC backlight
> interface should only be exposed when the system is in dynamic mode
> (different vendors may call this differeint things in the EFI setup
> menus), and the native backlight interfaces for the GPUs, be they
> discrete or integrated, should only be exposed when a mode that keeps
> only one of the GPUs connected to the panel; i.e., in discrete-only mode
> the discrete GPU should have a working native backlight interface, and
> in integrated-only mode, or a hybrid mode which does not allow dynamic
> mux switching, the integrated GPU should have a working native backlight
> interface.
>
> For this notebook the AMD GPU would be the integrated one, so if the
> system is *not* in dynamic switch mode, and the WMI interface is
> reporting that the backlight should be handled by the EC, then that is
> certainly a bug in the system, and this would be the correct workaround,
> when the system is operating in an iGPU-only or non-dynamic hybrid mode.
> However, if the system is switched to a dynamic mode, then this would
> break the EC backlight, which should be the corect backlight interface
> for that case. Another possible system bug would be if the condition
> described in the change description occurs when the system *is* in a
> dynamic mode, but is routing backlight control to the iGPU anyway. That
> would be a messier bug to deal with, since it would also be necessary to
> determine which backlight interface is functional when the display is
> switched over to the dGPU.
>
> If it's not too much trouble could you (or the reporter, if you don't
> have the system) check which backlight interfaces are exposed, and which
> of those actually work, for each of the different hybrid GPU modes? I am
> not certain what they would be called on the setup screen, but the
> possible modes should be:
>
> * Integrated only
> * Discrete only
> * Hybrid, without dynamic switching
> * Hybrid, with dynamic switching
>
> , or a subset thereof. Usually I would expect the minimal subset to be
> discrete only plus one or both of the hybrid modes. Since we're not sure
> what these are called on the setup screen it is probably best to simply
> report the names of the mode as they are listed in the UI.
Isn't the whole idea behind nvidia-wmi-ec-backlight that the backlight's
pwm input is connected to the EC (it is sorta in the name) and then always
is controlled by the EC independent of the mode ?
At least I was under the impression that that was the whole idea?
I will forward your email to the reporter and ask them to get
in touch with you and then lets see from there.
Regards,
Hans
>
>> Cc: Daniel Dadap <ddadap@xxxxxxxxxx>
>> Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
>> ---
>> drivers/acpi/video_detect.c | 10 ++++++++++
>> 1 file changed, 10 insertions(+)
>>
>> diff --git a/drivers/acpi/video_detect.c b/drivers/acpi/video_detect.c
>> index 841f6213b4de..88acc09773bb 100644
>> --- a/drivers/acpi/video_detect.c
>> +++ b/drivers/acpi/video_detect.c
>> @@ -645,6 +645,16 @@ static const struct dmi_system_id video_detect_dmi_table[] = {
>> },
>> },
>>
>> + /* Models which have nvidia-ec-wmi support, but should not use it. */
>> + {
>> + .callback = video_detect_force_native,
>> + /* Dell G15 5515 */
>> + .matches = {
>> + DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."),
>> + DMI_MATCH(DMI_PRODUCT_NAME, "Dell G15 5515"),
>> + },
>> + },
>> +
>> /*
>> * Desktops which falsely report a backlight and which our heuristics
>> * for this do not catch.
>> --
>> 2.37.3
>>
>
