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

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Message-ID: <5547F67D.2080307@amd.com>
Date:	Mon, 4 May 2015 17:45:17 -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 5/3/2015 11:13 AM, Aravind Gopalakrishnan wrote:
>
> On 5/1/15 7:42 PM, Aravind Gopalakrishnan wrote:
>>
>> On 5/1/15 5:47 PM, Borislav Petkov wrote:
>>> 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.

Tested a delay of 0 on Fam10h and Fam15h Model 30h-3fh and both work fine.

Feedback from asking internally about this is that we should be OK to 
move to a no-delay default from K8 onwards.

Thanks,
-Aravind.
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