linux-kernel - Re: [PATCH v3 09/17] ARM64 / ACPI: Parse MADT for SMP initialization

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Date:	Tue, 09 Sep 2014 13:11:59 +0800
From:	Hanjun Guo <hanjun.guo@...aro.org>
To:	Jon Masters <jcm@...hat.com>
CC:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Mark Rutland <Mark.Rutland@....com>,
	Olof Johansson <olof@...om.net>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	"graeme.gregory@...aro.org" <graeme.gregory@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	Sudeep Holla <Sudeep.Holla@....com>,
	Will Deacon <Will.Deacon@....com>,
	Jason Cooper <jason@...edaemon.net>,
	Marc Zyngier <Marc.Zyngier@....com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Mark Brown <broonie@...nel.org>, Rob Herring <robh@...nel.org>,
	Robert Richter <rric@...nel.org>,
	Lv Zheng <lv.zheng@...el.com>,
	Robert Moore <robert.moore@...el.com>,
	Liviu Dudau <Liviu.Dudau@....com>,
	Randy Dunlap <rdunlap@...radead.org>,
	Charles Garcia-Tobin <Charles.Garcia-Tobin@....com>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 09/17] ARM64 / ACPI: Parse MADT for SMP initialization

On 2014年09月09日 12:29, Jon Masters wrote:
> Hi Hanjun, Lorenzo,

Hi Jon,

>
> Resending due to my mail client removing list CCs...sorry about that.
>
> On 09/04/2014 11:29 AM, Hanjun Guo wrote:
>
>>>> +	} else {
>>>> +		/* Fist GICC entry must be BSP as ACPI spec said */
>>> s/Fist/First/
>>>
>>>> +		if  (cpu_logical_map(0) != mpidr) {
>>>> +			pr_err("First GICC entry is not BSP for MPIDR 0x%llx\n",
>>>> +			       mpidr);
>>>> +			return -EINVAL;
>>>> +		}
>>> Interesting, this means that if I want to change the boot CPU I have to
>>> recompile the ACPI tables. Is that really true ?
> Well, the ACPI5.1 specification does require that the PEs (cores) be
> listed in a very specific order, with the boot CPU first, and then a
> precisely defined sequence of interleaving of any possible SMT threads
> with other cores. So I think you would in practice update your tables.

Thanks for the clarify.

>
>>>> +	/*
>>>> +	 * ACPI 5.1 only has two explicit methods to boot up SMP,
>>>> +	 * PSCI and Parking protocol, but the Parking protocol is
>>>> +	 * only specified for ARMv7 now, so make PSCI as the only
>>>> +	 * way for the SMP boot protocol before some updates for
>>>> +	 * the ACPI spec or the Parking protocol spec.
>>>> +	 */
> The Parking Protocol may be updated for a (limited) number of platforms
> that may use it in the early days. The preferred option (as described in
> the SBBR) is to use PSCI when at all possible. Some implementations of
> the architecture may not be able to use PSCI for MP-Boot. Thus while
> there may be some limited early use of the parking protocol (including
> while PSCI firmware is being finalized during bringup activities), it
> will ultimately be completely replaced by PSCI based boot over time.

Thank you for the clarify again :)

Will Parking Protocol be upstreamed? If yes, I think we can update the
comments when Parking Protocol driver upstreamed.

Thanks
Hanjun 

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