On Thu, Dec 10, 2020 at 1:06 AM Daniel Scally <djrscally@xxxxxxxxx> wrote:
>
> On 09/12/2020 16:53, Rafael J. Wysocki wrote:
> > On Wed, Dec 9, 2020 at 5:20 PM Daniel Scally <djrscally@xxxxxxxxx> 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@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.
> > 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)?
