Re: acpi_device_notify() binding devices that don't seem like they should be bound

[Daniel Scally <djrscally@gmail.com>]

On 10/12/2020 13:53, Rafael J. Wysocki wrote:
> On Thu, Dec 10, 2020 at 1:06 AM Daniel Scally <djrscally@gmail.com> wrote:
>> On 09/12/2020 16:53, Rafael J. Wysocki wrote:
>>> On Wed, Dec 9, 2020 at 5:20 PM Daniel Scally <djrscally@gmail.com> wrote:
>>>> Hi Rafael
>>>>
>>>> On 09/12/2020 15:43, Rafael J. Wysocki wrote:
>>>>> On Wed, Dec 9, 2020 at 10:55 AM Daniel Scally <djrscally@gmail.com> 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.
>>> That's correct.
>> OK, that definitely makes it harder then. Sort of clutching at straws
>> here; is _ADR=0 a special case in any way? As far as I can tell it's
>> only a problem on my devices for that address but that could easily be
>> coincidence.
>>>>> 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.
>>> That's the intended outcome.
>>>
>>> We may need another value (between the min and the max) to return when
>>> adev->pnp.type.platform_id is not set and _STA is not present.
>>
>> Unfortunately this turns out not to be the problem in this case; on
>> checking for _STA too, all the potential devices except the 2 cameras
>> and their dependee PMICs have a _STA present but set 0,
> Which means that they shouldn't be used.
>
>> so find_child_checks() throws -ENODEV; and downweights them below the devs
>> that shouldn't match.
> OK, so we want acpi_find_child_device() to return NULL in this case.
>
> What about making it return NULL if there is a matching device with
> _ADR and without _HID that is unusable (ie. _STA == 0)?

All the adevs with matching _ADR also have both _STA and _HID
unfortunately. Sorry; let me stop half-arsing this and show you
something useful:


[    0.219953] acpi_find_child_device(PNP0A08:00, 0x00, false)
[    0.220818] INT3472:00: _STA 0x00, _ADR=0x00000000, _HID=INT3472
[    0.220821] INT3472:01: _STA 0x00, _ADR=0x00000000, _HID=INT3472
[    0.220870] INT3472:02: _STA 0x00, _ADR=0x00000000, _HID=INT3472
[    0.220892] INT3472:03: _STA 0x00, _ADR=0x00000000, _HID=INT3472
[    0.220916] INT3472:04: _STA 0x00, _ADR=0x00000000, _HID=INT3472
[    0.220941] INT3472:05: _STA 0x00, _ADR=0x00000000, _HID=INT3472
[    0.220965] INT3472:06: _STA 0x00, _ADR=0x00000000, _HID=INT3472
[    0.220990] INT3472:07: _STA 0x00, _ADR=0x00000000, _HID=INT3472
[    0.221038] INT3472:08: _STA 0x0f, _ADR=0x00000000, _HID=INT3472
[    0.221051] OVTI5648:00: _STA 0x0f, _ADR=0x00000000, _HID=OVTI5648
[    0.221061] INT3472:09: _STA 0x0f, _ADR=0x00000000, _HID=INT3472
[    0.221070] OVTI2680:00: _STA 0x0f, _ADR=0x00000000, _HID=OVTI2680
[    0.221079] INT3471:00: _STA 0x00, _ADR=0x00000000, _HID=INT3471
[    0.221105] INT33BE:00: _STA 0x00, _ADR=0x00000000, _HID=INT33BE
[    0.221130] INT3471:01: _STA 0x00, _ADR=0x00000000, _HID=INT3471
[    0.221156] INT33BE:01: _STA 0x00, _ADR=0x00000000, _HID=INT33BE


That's the debug output I included for each adev that's assessed as a
child of PNP0A08:00. _STA, _ADR and _HID present for all, _ADR 0x00 for
all, _STA 0x0f for the 2 sensors and their PMIC's and 0x00 for the rest.
The same situation holds on both of my devices.