drm/i915/opregion: work around buggy firmware that provides 8+ output devices

On 02/13/2014 08:03 PM, Daniel Vetter wrote:
> On Thu, Feb 13, 2014 at 11:08 AM, Chris Wilson <chris@chris-wilson.co.uk> wrote:
>> On Thu, Feb 13, 2014 at 05:10:25PM +0800, Aaron Lu wrote:
>>> On 02/12/2014 06:31 PM, Chris Wilson wrote:
>>>> On Wed, Feb 12, 2014 at 11:05:40AM +0800, Aaron Lu wrote:
>>>>> The ACPI table on ASUS UX302LA has more than 8 output devices under the
>>>>> graphics controller device node. The problem is, the real active output
>>>>> device, the LCD panel, is listed the last. The result is, the LCD's
>>>>> device id doesn't get recorded in the active device list CADL array and
>>>>> when the _DCS control method for the LCD device is executed, it returns
>>>>> 0x1d, meaning it is not active. This affects the hotkey delivery ASL
>>>>> code that will not deliver a notification if the output device is not
>>>>> active on backlight hotkey press.
>>>>>
>>>>> I don't see a clean way to solve this problem since the operation region
>>>>> spec doesn't allow more than 8 output devices so we have no way of
>>>>> storing all these output devices. The fact that output devices that have
>>>>> _BCM control method usually means they have a higher possibility of being
>>>>> used than those who don't made me choose a simple way to work around
>>>>> the buggy firmware by replacing the last entry in CADL array with the one
>>>>> that has _BCM control method. There is no specific reason why the last
>>>>> entry is picked instead of others.
>>>>
>>>> Another possibility is that the connector list is in rough priority
>>>> order so might be useful for sorting the CADL array.
>>>>
>>>> Since the CADL should only be a list of currently active devices, we
>>>> could just bite the bullet and repopulate it correctly after every
>>>> setcrtc.
>>>
>>> Thanks for the suggestion. As a first step, does the following un-tested
>>> patch look OK?
>>
>> Yes. Maybe worth putting together the similar routines for blind
>> setting the didl and the cadl, or at least for computing the value from
>> the connector. For instance, the didl logic disagrees with the value of
>> index - is that relevant? I have a suspicion that the CADL entry should
>> match the DIDL entry for the connector, but that is not actually
>> mentioned in the opregion spec afaict.
> 
> I think a problem is that often we have more than one output for a
> given type. So we need to somehow match them up to make sure we put
> the right ones intot didl/cadl lists. The issue here is that our
> connectors don't match up perfectly with the acpi output entries
> (since we have separate dp/hdmi outputs). But I think it would be
> worthwhile trying to match them up and store a link from struct
> intel_connector to the right acpi node acpi node.

Is this possible? I don't see a way to match them up...
The _ADR control method uses a field that seems to be assigned by BIOS
like this:

                Device (LCDD)
                {
                  Method (_ADR, 0, Serialized)  // _ADR: Address
                    {
                        Return (And (0xFFFF, DID2))
                    }
		}
DID2 is in system memory region and has some assigned value like 0x400
when we read it. For this case it is easy since there is only one output
device that is of type LVDS so we can match it to connector of type eDP
or LVDS, suppose there is only one such connector. But for output
devices' whose _ADR has the value of 0x301, 0x302, etc. I have no idea
how to match them up to the connectors of that type as we can't be sure
the probe order we have used in i915 driver is the same as BIOS'.

In the mean time, it seems we can just use driver's information to
populate both DIDL and CADL and forget the _ADR of those devices like
the following patch does:

I've tested the patch locally on some laptops but I've no idea of what
impact it has on others.

Thanks,
Aaron

drm/i915/opregion: work around buggy firmware that provides 8+ output devices

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