Macbook Air 6, 2: i915-related interrupt storm after Yosemite update

Macbook Air 6, 2: i915-related interrupt storm after Yosemite update

[Christian Kastner]

Hi,

I have a Macbook Air (2013) (6,2) which until recently was working
flawlessly with Debian unstable, which I use almost exclusively on that
machine. I did keep the OSX installation, mainly because it's the only
way to get firmware updates.

Recently, in a moment of weakness, I said "yes" to the offer of
upgrading OSX to Yosemite. Since then, whenever I boot Debian, there is
an i915-related interrupt storm, with a kworker thread constantly
running at 70%.

Downgrading OSX back to Mavericks did not help. Apparently Yosemite
included firmware updates, as within OSX I am shown version numbers that
are so new they aren't even listed on Apple's homepage yet.

Here's what I see:

  $ GPE=/sys/firmware/acpi/interrupts/gpe66
  $ while true; doe cat $GPE; sleep 1; done
  727268   enabled
  757981   enabled
  788576   enabled
  807337   enabled
  828426   enabled
        ...

I've tested this with 3.16 and 3.17 kernels; I was using the former for
about a month now without issue.

When I boot with modprobe.blacklist=i915, the issue disappears.

Does anyone have an idea what could be going on?

Regards,
Christian


PS: Please CC: me as I am not subscribed to this list.



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Re: Macbook Air 6, 2: i915-related interrupt storm after Yosemite update

[Daniel Vetter]

On Sat, Nov 01, 2014 at 06:08:00PM +0100, Christian Kastner wrote:
> Hi,
> 
> I have a Macbook Air (2013) (6,2) which until recently was working
> flawlessly with Debian unstable, which I use almost exclusively on that
> machine. I did keep the OSX installation, mainly because it's the only
> way to get firmware updates.
> 
> Recently, in a moment of weakness, I said "yes" to the offer of
> upgrading OSX to Yosemite. Since then, whenever I boot Debian, there is
> an i915-related interrupt storm, with a kworker thread constantly
> running at 70%.
> 
> Downgrading OSX back to Mavericks did not help. Apparently Yosemite
> included firmware updates, as within OSX I am shown version numbers that
> are so new they aren't even listed on Apple's homepage yet.
> 
> Here's what I see:
> 
>   $ GPE=/sys/firmware/acpi/interrupts/gpe66
>   $ while true; doe cat $GPE; sleep 1; done
>   727268   enabled
>   757981   enabled
>   788576   enabled
>   807337   enabled
>   828426   enabled
>         ...
> 
> I've tested this with 3.16 and 3.17 kernels; I was using the former for
> about a month now without issue.
> 
> When I boot with modprobe.blacklist=i915, the issue disappears.
> 
> Does anyone have an idea what could be going on?

The only acpi interrupt we're handling is asle afaik, so sounds like
something we do in there doesn't please the new firmware and sends it into
a tailspin. So I'd sprinkle printks all over the place there until you
know what exactly goes on in i915, starting with the asle functions.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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Re: Macbook Air 6, 2: i915-related interrupt storm after Yosemite update

[Christian Kastner]

On 2014-11-03 16:25, Daniel Vetter wrote:
> On Sat, Nov 01, 2014 at 06:08:00PM +0100, Christian Kastner wrote:
>>
>> [after upgrading dual-booted OSX to Yosemite, wich included firmware updates]
>>
>> Here's what I see [in Linux 3.16, 3.17]:
>>
>>   $ GPE=/sys/firmware/acpi/interrupts/gpe66
>>   $ while true; do cat $GPE; sleep 1; done
>>   727268   enabled
>>   757981   enabled
>>   788576   enabled
>>   807337   enabled
>>   828426   enabled
>>         ...
>> When I boot with modprobe.blacklist=i915, the issue disappears.
>>
>> Does anyone have an idea what could be going on?
> 
> The only acpi interrupt we're handling is asle afaik, so sounds like
> something we do in there doesn't please the new firmware and sends it into
> a tailspin. So I'd sprinkle printks all over the place there until you
> know what exactly goes on in i915, starting with the asle functions.

In the meantime, I noticed that there a kernel bugzilla bug entry for
this issue.

    https://bugzilla.kernel.org/show_bug.cgi?id=85881

It has been closed in the meantime, although AFAIUI it the solution
merely forces disabling gpe66.

I'd still like try resolving this by determining the cause. Before I
embark on an unguided printk spree: does this analysis from the bugzilla
bug perhaps somewhat narrow the issue down so that I can focus on a
specific part?

Comment #31 from Lv Zheng <lv.zheng@intel.com>
> The decompiled GPE 0x66 handler is as follows:
>         Method (_L66, 0, NotSerialized)  // _Lxx: Level-Triggered GPE
>         {
>             If (LAnd (\_SB.PCI0.IGPU.GSSE, LNot (GSMI)))
>             {
>                 \_SB.PCI0.IGPU.GSCI ()
>             }
>             Else
>             {
>                 Store (0x00, \_SB.PCI0.IGPU.GEFC)
>                 Store (0x01, SCIS) /* \SCIS */
>                 Store (0x00, \_SB.PCI0.IGPU.GSSE)
>                 Store (0x00, \_SB.PCI0.IGPU.SCIE)
>             }
>         }
> It's completely GPU related. So I have no idea what has happened.
> The GSMI seems to be some configuration option in the BIOS:
>     OperationRegion (GNVS, SystemMemory, 0x8CD3EA90, 0x026D)
>     Field (GNVS, AnyAcc, Lock, Preserve)
>     {
>         GSMI,   8, 
>     }
> It sounds like something was originally handled by SMI and now is reported
> through GPE. So I guess there might be chances you could revert back to the
> original behavior using some BIOS configuration.

[note: TTBOMK no such low-level configuration is possible]

Christian
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Re: Macbook Air 6, 2: i915-related interrupt storm after Yosemite update -- resolved

[Christian Kastner]

On 2014-11-01 18:08, Christian Kastner wrote:
> I have a Macbook Air (2013) (6,2) which until recently was working
> flawlessly with Debian unstable, which I use almost exclusively on that
> machine. I did keep the OSX installation, mainly because it's the only
> way to get firmware updates.
> 
> Recently, in a moment of weakness, I said "yes" to the offer of
> upgrading OSX to Yosemite. Since then, whenever I boot Debian, there is
> an i915-related interrupt storm, with a kworker thread constantly
> running at 70%.
> 
> Downgrading OSX back to Mavericks did not help. Apparently Yosemite
> included firmware updates, as within OSX I am shown version numbers that
> are so new they aren't even listed on Apple's homepage yet.
> 
> Here's what I see:
> 
>   $ GPE=/sys/firmware/acpi/interrupts/gpe66
>   $ while true; doe cat $GPE; sleep 1; done
>   727268   enabled
>   757981   enabled
>   788576   enabled
>   807337   enabled
>   828426   enabled
>         ...
> 
> I've tested this with 3.16 and 3.17 kernels; I was using the former for
> about a month now without issue.
> 
> When I boot with modprobe.blacklist=i915, the issue disappears.
> 
> Does anyone have an idea what could be going on?

Good news: the recent update of OSX to 10.10.2 contained another silent
firmware update, and it appears that this update resolved the issue.

Regards,
Christian
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