Re: [PATCH] ACPI: x86: Apple T2 systems need early CPU offlining

["Chen, Yu C" <yu.c.chen@intel.com>]

Thanks Lukas for bringing this up,

On 8/15/2026 11:43 PM, Lukas Wunner wrote:
> [cc += Chen Yu, start of thread is here:
> https://lore.kernel.org/all/20260812120326.155226-1-dev@deq.rocks/
> ]
> 
> On Wed, Aug 12, 2026 at 02:03:26PM +0200, Andre Eikmeyer wrote:
>> Linux reports _OSI("Darwin") on x86 Apple systems. On T2 Macs, the
>> selected firmware suspend path makes secondary CPU startup during early
>> resume take several seconds per CPU.
> 
> That's not a T2-specific issue.  It occurs on older Intel Macs as well.
> 
> Back in 2018, Chen Yu root-caused it to an invalid MTRR upon resume
> from system sleep:
> 
> https://lore.kernel.org/all/20180319041843.28218-1-yu.c.chen@intel.com/
> 
> I've been using his patch for 8 years to reduce resume time on my
> MacBookPro9,1.  Unfortunately it was never applied upstream for
> reasons unknown.  It probably just slipped through the cracks.
> 
> You may want to test if his patch helps on T2 models as well.
> I think it's a more generic solution to the problem than the one
> you're proposing.
> 

Glad it helped! At that time, it seemed that the issue might have
been related to broken Mac platforms, and we were changing the
generic x86 path. Maybe we can wait for Andre's feedback, I
can try again / or assist Andre - or just keep it out-of-tree;
that's also fine.

thanks,
Chenyu