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

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Date:	Sun, 12 Apr 2015 00:57:02 +0800
From:	Jiang Liu <jiang.liu@...ux.intel.com>
To:	Jim Bos <jim876@...all.nl>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-pm@...r.kernel.org
Subject: Re: [PATCH] x86/ACPI: Fix regression caused by 16ee7b3dcc56 & c50f13c672df7

On 2015/4/11 23:08, Jim Bos wrote:
> 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@...el.com>
> 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!
Hi Jim,
	Thanks for your great effort to bisect the regression.
And it gets reasonable now:)
Thanks!
Gerry

> 
> Jim
> 
> 
> 
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