linux-kernel - Re: Getting rid of i7300

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Message-ID: <20150605065219.GA19628@gmail.com>
Date:	Fri, 5 Jun 2015 08:52:19 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Andy Lutomirski <luto@...nel.org>,
	Andy Henroid <andrew.d.henroid@...el.com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>, X86 ML <x86@...nel.org>,
	Matthew Garrett <mjg59@...f.ucam.org>
Subject: Re: Getting rid of i7300_idle's idle notifier?


* Andy Lutomirski <luto@...capital.net> wrote:

> On Thu, Jun 4, 2015 at 4:32 PM, Andy Lutomirski <luto@...nel.org> wrote:
>
> > AFAICT the sole purpose for the hideous x86_64 idle_notifier mess is to 
> > support i7300_idle.  IMO this junk does not belong in IRQ handling, etc.  Can 
> > we redo this to work in some kind of generic way?
> >
> > I have no idea why it makes sense to twiddle I/O AT registers in the beginning 
> > of whatever IRQ wakes up the CPU.
> >
> > Note that, if absolutely necessary, the ECX bit 0 MWAIT extension can be used 
> > to reliably execute code before handling interrupts that wake us from idle.  
> > That is, there could be a real cpuidle driver for that chip that does:
> >
> > cli;
> > poke ioat;
> > mwait(ecx = 1);
> > poke ioat;
> > sti;
> >
> > Or we could delete the driver entirely.
> 
> It's even easier than that.  Just shove the hooks into acpi_idle_do_entry or 
> similar and remove them from every other exit_idle call site in the kernel.

Yes!

Interested in doing a patch?

Thanks,

	Ingo
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