linux-kernel - Re: Ask help about pre_init_apic

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Date:	Thu, 11 Sep 2014 18:15:03 +0300
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Jiang Liu <jiang.liu@...ux.intel.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	x86@...nel.org
Subject: Re: Ask help about pre_init_apic_IRQ0()

On Thu, 2014-09-11 at 16:35 +0200, Thomas Gleixner wrote:
> On Thu, 11 Sep 2014, Andy Shevchenko wrote:
> > On Thu, 2014-09-11 at 14:58 +0200, Thomas Gleixner wrote:
> > []
> > 
> > > According to the MID code the apbt horror is only used for moorestown.
> > > Medfield and later use the local apic timer without the apbt nonsense.
> > > 
> > > The best thing we can do is to drop moorestown support and get rid of
> > > that apbt nonsense alltogether.
> > 
> > Alan Cox removed Moorestown (as a platform) support in 2012 IIRC.
> > So, AFAIK you may safely remove those leftovers.
> 
> Good.
>  
> > > I don't think anyone deeply cares about it not being supported from
> > > 3.18 on. The number of devices which sport a moorestown should be
> > > pretty limited and the only relevant use case of those is to act as a
> > > pocket heater with short battery life time. Its pretty pointless to
> > > update kernels on pocket heaters except for bragging reasons.
> > > 
> > > If someone at Intel really thinks that we need to keep moorestown
> > > alive for other than documentary and sentimental reasons, then we can
> > > move the apbt setup to x86_init.timers.setup_percpu_clockev(). At that
> > > point the IOAPIC is setup already, so it should just work. Untested
> > > patch below.
> > 
> > Suddenly I have one priority work to do and my Medfield tablet doesn't
> > boot by some reason. I would try to test it as soon as I can.
> 
> The patch wont make a difference, except you add

With patch nothing happened indeed.


>      x86_intel_mid_timer=apbt_only

[    0.116839] BUG: unable to handle kernel NULL pointer dereference at
0000003a
[    0.123803] IP: [<c1071c0e>] setup_irq+0xf/0x4d
...

> or
>      x86_intel_mid_timer=lapic_and_apbt

[    0.116858] BUG: unable to handle kernel NULL pointer dereference at
0000003a
[    0.123820] IP: [<c1071c0e>] setup_irq+0xf/0x4d
...

> 
> on the kernel commandline. But even w/o that patch I doubt that
> anything post moorestown even has that apbt trainwreck implemented. If
> I'm right then the commandline option will prevent the thing to boot
> at all, which is an even better reason to remove that crap
> alltogether.

See above.

> 
> Thanks,
> 
> 	tglx
> 
> 
> 
> 


-- 
Andy Shevchenko <andriy.shevchenko@...el.com>
Intel Finland Oy

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