Re: [PATCH] ACPI / scan: Prefer devices without _HID/_CID for _ADR matching

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On Friday, March 31, 2017 12:39:35 PM Hans de Goede wrote:
> Hi,
> 
> On 30-03-17 22:56, Rafael J. Wysocki wrote:
> > On Sunday, January 01, 2017 09:30:06 PM Hans de Goede wrote:
> >> Hi,
> >>
> >> On 30-12-16 02:27, Rafael J. Wysocki wrote:
> >>> From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> >>>
> >>> The way acpi_find_child_device() works currently is that, if there
> >>> are two (or more) devices with the same _ADR value in the same
> >>> namespace scope (which is not specifically allowed by the spec and
> >>> the OS behavior in that case is not defined), the first one of them
> >>> found to be present (with the help of _STA) will be returned.
> >>>
> >>> This covers the majority of cases, but is not sufficient if some of
> >>> the devices in question have a _HID (or _CID) returning some valid
> >>> ACPI/PNP device IDs (which is disallowed by the spec) and the
> >>> ASL writers' expectation appears to be that the OS will match
> >>> devices without a valid ACPI/PNP device ID against a given bus
> >>> address first.
> >>>
> >>> To cover this special case as well, modify find_child_checks()
> >>> to prefer devices without ACPI/PNP device IDs over devices that
> >>> have them.
> >>>
> >>> Suggested-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
> >>> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> >>> ---
> >>>
> >>> I'm not actually sure if this is sufficient to fix the original 80860F14 uid "2"
> >>> sd-controller problem on CherryTrail.  Hans, can you please check?
> >>
> >> Ok, just booted a kernel with this patch replacing my own attempt
> >> at fixing this, and the kernel still sees and initializes the
> >> mmc controller in question correctly with this patch:
> >>
> >> Tested-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> >
> > Unfortunately, this breaks discrete graphics enumeration in
> >
> > https://bugzilla.kernel.org/show_bug.cgi?id=194889
> >
> > so can you please check if the patch below doesn't break the platform fixed by
> > the above?
> 
> I've just tried this and this patch does not regress the platform fixed
> by the original commit.

OK, thanks!

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