Re: [PATCH] x86/ACPI: Fix regression caused by 16ee7b3dcc56 & c50f13c672df7

[Jim Bos]

On 04/10/2015 03:56 AM, Jiang Liu wrote:
> On 2015/4/10 0:41, Jim Bos wrote:
>> On 04/09/2015 12:15 PM, Jiang Liu wrote:
>>> On 2015/4/8 23:51, Jim Bos wrote:
>>>> On 04/08/2015 07:26 AM, Jiang Liu wrote:
>>>>> On 2015/4/8 0:49, Jim Bos wrote:
>>>>>> On 04/07/2015 04:34 PM, Jiang Liu wrote:
> <snip>
>>> Hi Jim,
>>> 	I'm really confused. I can't even explain why my previous
>>> patch fixes the issue on AMD geode board now:(
>>>
>>> For the Dell laptop, seems you have:
>>> 1) build a kernel with Local APIC and IOAPIC enabled
>>> 2) lapic is disabled by BIOS, so there's no ACPI MADT(APIC)
>>> table at all.
>>> That means the laptop is working with 8259 PICs only.
>>> There's little change between 3.16 and 4.0 related to 8259.
>>>
>>> For the AMD geode board, I still think original code is right.
>>> I can't explain why the patch fix the issue.
>>>
>>> So could you please help to:
>>> 1) Try to enable lapic on Dell laptop in BIOS
>>> 2) Dump acpi tables and dmesg on AMD board
>>>
>>> If that still doesn't help, I will try to send you some
>>> debug patches to gather more info.
>>> Thanks!
>>> Gerry
>>>> _
>>>> Jim
>>>>
>>>
>>
>> Gerry,
>>
>> As you mentioned your patch shouldn't make a difference, run some more
>> tests, as it turns out:
>> - geode system  broken on 3.16+ up to and including 3.19, however, on
>> plain 4.0-rc6 it works!  Root cause appears to be there isn't an ACPI
>> interrupt assigned in non-working kernels.
>> - other system I got my hands on: Pentium(R) CPU G3220, broken on 3.19.0
>> when boot parameter 'nosmp' is specified, again no acpi entry in
>> /proc/interrupts,  working fine on 4.0-rc6
>>
>> So obviously between 3.19 and 4.0-rc6 something got fixed here!
> Hi Jim,
> Yes, the bugfix patch should be:
> commit 1ea76fbadd66("x86/irq: Fix regression caused by commit b568b8601f05")
> 
>> The Dell laptop remains the only problem then on 4.0-rc6, there IS an
>> acpi interrupt  (but firing once apparently).
>> There isn't an option in BIOS to enable LAPIC, however, when specifying
>> 'lapic' as boot parameter I got interesting result, still not working
>> and /proc/interrups still shows XT-PIC.  Doing a diff between dmesg on
>> 3.19 and 4.0-rc6 this pops out:
>>
>> -Local APIC disabled by BIOS -- you can enable it with "lapic"
>> -APIC: disable apic facility
>> -APIC: switched to apic NOOP
>> +Local APIC disabled by BIOS -- reenabling.
>> +Found and enabled local APIC!
>>
>> +Enabling APIC mode:  Flat.  Using 0 I/O APICs
> What's the last know working kernel for Dell laptop?
> Does it work as expected with v3.19 kernel?
> Do you means this message is from plain v4.0-rc6 kernel?
> Thanks!
> Gerry
> 
>>
>> Jim
>>
> 

Gerry, Rafael,

Ok, found it.
It was very 'interesting' bisect, because there were 2 overlapping
issues here.  On the Dell laptop some kernels there wasn't an ACPI
interrupt at all or it fired once and then seemed to get stuck.
Turns out that kernel version:
3.16: OK
3.17: Broken (no acpi interrupt)
3.18: actually fine
3.19: Broken

So started bisecting between 3.18 or 3.19, in the end found Rafael's
patch which broke it:

==
commit c50f13c672df758b59e026c15b9118f3ed46edc4
Author: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Date:   Mon Dec 1 23:50:16 2014 +0100

    ACPICA: Save current masks of enabled GPEs after enable register writes
==

Reverting that patch on top of 4.0-rc7 (with some offsets and one
trivial manual edit) and I finally got a working ACPI interrupt again!

Jim



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