Hi Rafael
On 09/12/2020 15:43, Rafael J. Wysocki wrote:
> On Wed, Dec 9, 2020 at 10:55 AM Daniel Scally <djrscally@xxxxxxxxx> wrote:
>>
>>
>> On 08/12/2020 23:48, Daniel Scally wrote:
>>> Hello again
>>>
>>> On 06/12/2020 00:00, Daniel Scally wrote:
>>>> INT3472:08 is not an acpi device that seems to be a good candidate for
>>>> binding to 0000:00:00.0; it just happens to be the first child of
>>>> PNP0A08:08 that shares _ADR 0 and has _STA not set to 0.
>>>>
>>>> The comment within acpi_find_child_device() does imply that there should
>>>> only ever be a single child device with the same _ADR as the parent, so
>>>> I suppose this is possibly a case of poor ACPI tables confusing the code
>>>> a bit; given both PNP0A08:00 and _all_ of the INT3472 devices have _ADR
>>>> set to zero (as indeed do the machine's cameras), but I'm not
>>>> knowledgeable enough on ACPI to know whether that's to spec (or at least
>>>> accounted for). The INT3472 devices themselves do not actually seem to
>>>> represent a physical device (atleast, not in this case...sometimes they
>>>> do...), rather they're a dummy being used to simply group some GPIO
>>>> lines under a common _CRS. The sensors are called out as dependent on
>>>> these "devices" in their _DEP method, which is already a horrible way of
>>>> doing things so more broken ACPI being to blame wouldn't surprise me.
>>>>
>>>> The other problem that that raises is that there seems to be _no_ good
>>>> candidate for binding to 0000:00:00.0 that's a child of PNP0A08:00 - the
>>>> only devices sharing _ADR 0 and having _STA != 0 are those two INT3472
>>>> entries and the machine's cameras.
>>> After some more reading, I'm pretty confident that this is the problem
>>> now - I.E. that those devices having _ADR of 0 is what's causing this
>>> issue to materialise, and that those values should be set to something
>>> more appropriate. Still unsure about the best approach to fix it though
>>> from a kernel point of view; there doesn't seem to be anything out of
>>> whack in the logic, and I believe (correct me if I'm wrong) there can be
>>> legitimate instances of child devices sharing _ADR=0 with the parent, so
>>> the problem becomes how to identify the illegitimate instances so that
>>> they can be discarded. My experience in this is really limited, so I
>>> lean towards the conclusion that hard-coding exceptions somewhere might
>>> be necessary to handle this without resorting to patched ACPI tables.
>>> Whether that's within acpi_find_child_device() to prevent matching
>>> occurring there, or else setting the adev->pnp.bus_address to some
>>> alternate value after creation to compensate.
>>>
>>> I recognise that that's a horrible answer though, so I'm really hoping
>>> that someone has an idea for how to handle this in a better way.
>> Oops, missed this crucial line from the spec:
>>
>> "A device object must contain either an _HID object or an _ADR object,
>> but should not contain both."
>>
>> And here's the Device declaration for these objects:
>>
>> Device (PMI0)
>> {
>> Name (_ADR, Zero) // _ADR: Address
>> Name (_HID, "INT3472") // _HID: Hardware ID
>> Name (_CID, "INT3472") // _CID: Compatible ID
>> Name (_DDN, "INCL-CRDD") // _DDN: DOS Device Name
>> Name (_UID, Zero) // _UID: Unique ID
>>
>> So that's the broken part rather than the _ADR value of 0 specifically.
>> That at least gives a jumping off point for some logic to fix rather
>> than a hardcoded anything, so I'll try to work out a nice way to handle
>> that (probably ignoring adevs in acpi_find_child_device() with addr=0
>> and a valid _HID) and submit a patch.
> Please see the comment in find_child_checks(), though - it kind of
> tries to handle this case already.
It down-weights them currently yes, but does still allow them to match.
I think it makes more sense to not allow a match at all, at least in the
situation I've encountered, but I suppose the implication of the logic
in this check is that at some point we've encountered ACPI entries with
both _HID and _ADR that were potentially correct matches, which kinda
re-complicates things again.
>
> I guess what happens is that _STA is not present under the device that
> is expected to be matched, so maybe the logic regarding this may be
> changed somewhat.
Hmm yeah I guess so, so this is kinda a combination of two problems
probably. And if the actual device that is expected to match had a _STA
> 0 then presumably the down-weighting of devices with a _HID in
find_child_checks() would ensure the correct dev was matched.
>> Sorry for the noise, think I'm good now :)
> OK
