linux-kernel - Re: [PATCH 0/1] speeding up cpu

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Message-ID: <55464925.5050600@amd.com>
Date:	Sun, 3 May 2015 11:13:25 -0500
From:	Aravind Gopalakrishnan <aravind.gopalakrishnan@....com>
To:	Borislav Petkov <bp@...en8.de>, Len Brown <lenb@...nel.org>
CC:	Ingo Molnar <mingo@...nel.org>, X86 ML <x86@...nel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH 0/1] speeding up cpu_up()


On 5/1/15 7:42 PM, Aravind Gopalakrishnan wrote:
>
> On 5/1/15 5:47 PM, Borislav Petkov wrote:
>> On Fri, May 01, 2015 at 02:42:39PM -0700, Len Brown wrote:
>>> On Mon, Apr 20, 2015 at 12:15 AM, Ingo Molnar <mingo@...nel.org> wrote:
>>>
>>>> So instead of playing games with an ancient delay, I'd suggest we
>>>> install the 10 msec INIT assertion wait as a platform quirk instead,
>>>> and activate it for all CPUs/systems that we think might need it, with
>>>> a sufficiently robust and future-proof quirk cutoff condition.
>>>>
>>>> New systems won't have the quirk active and thus won't have to have
>>>> this delay configurable either.
>>> Okay, at this time, I think the quirk would apply to:
>>>
>>> 1. Intel family 5 (original pentium) -- some may actually need the 
>>> quirk
>>> 2. Intel family F (pentium4) -- mostly b/c I don't want to bother
>>> finding/testing p4
>>> 3. All AMD (happy to narrow down, if somebody can speak for AMD)
>> Aravind and I could probably test on a couple of AMD boxes to narrow 
>> down.
>>
>> @Aravind, see here:
>>
>> https://lkml.kernel.org/r/87d69aab88c14d65ae1e7be55050d1b689b59b4b.1429402494.git.len.brown@intel.com 
>>
>>
>> You could ask around whether a timeout is needed between the assertion
>> and deassertion of INIT done by the BSP when booting other cores.
>
> Sure, I'll ask around and try mdelay(0) on some systems as well.
> I can gather Fam15h, Fam16h but don't have K8's or older.
>
> Will let you know how it goes.
Update:
Fam15h Model00h-0fh, Fam15hModel60h and Fam16h Model 00h-0fh processors 
boot fine with mdelay(0) and BSP brings up all secondary cpus correctly. 
I don't have Fam15hModel30h system currently up, but I'll try that too 
tomorrow.

I am yet to get feedback from HW folks regarding this though.

Thanks,
-Aravind.

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