linux-kernel - Re: [PATCH v2 06/18] ARM64 / ACPI: Parse MADT to map logical cpu to MPIDR and get cpu_possible/present

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Date:	Thu, 21 Aug 2014 10:51:36 +0800
From:	Hanjun Guo <hanjun.guo@...aro.org>
To:	Catalin Marinas <catalin.marinas@....com>
CC:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Mark Rutland <Mark.Rutland@....com>,
	"graeme.gregory@...aro.org" <graeme.gregory@...aro.org>,
	Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	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>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....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" <linux-kernel@...r.kernel.org>,
	"linaro-acpi@...ts.linaro.org" <linaro-acpi@...ts.linaro.org>,
	Tomasz Nowicki <tomasz.nowicki@...aro.org>
Subject: Re: [PATCH v2 06/18] ARM64 / ACPI: Parse MADT to map logical cpu
 to MPIDR and get cpu_possible/present_map

On 2014-8-20 22:38, Catalin Marinas wrote:
> On Tue, Aug 19, 2014 at 08:36:46AM +0100, Hanjun Guo wrote:
>> On 2014-8-18 22:27, Catalin Marinas wrote:
>>> On Mon, Aug 04, 2014 at 04:28:13PM +0100, Hanjun Guo wrote:
>>>> diff --git a/arch/arm64/include/asm/acpi.h b/arch/arm64/include/asm/acpi.h
>>>> index 6e04868..e877967 100644
>>>> --- a/arch/arm64/include/asm/acpi.h
>>>> +++ b/arch/arm64/include/asm/acpi.h
>>>> @@ -64,6 +64,8 @@ static inline void arch_fix_phys_package_id(int num, u32 slot) { }
>>>>  extern int (*acpi_suspend_lowlevel)(void);
>>>>  #define acpi_wakeup_address 0
>>>>  
>>>> +#define MAX_GIC_CPU_INTERFACE 65535
>>>
>>> Does this need to be more than NR_CPUS?
>>
>> Sometimes yes, CPU structure entries in MADT just like CPU nodes in
>> device tree, the number of them may more than NR_CPUS.
> 
> I have a more general question here. In ACPI, is MADT the only way to
> build a CPU topology? 

Unfortunately yes as far as I can tell.

> It looks weird that we use GIC properties to
> create the cpu_logical_map(). 

Actually information in GICC structures in MADT will both used
for GIC init and SMP init, GICC structures represents CPUs in the
system.

> A side-effect is that the GIC-related
> functions are now scattered all over the kernel rather than being
> contained in the GIC driver itself.

As patch 12/18 shows, all the GIC related code all contained in the
GIC driver, GICC structure is more than GIC-related but also CPUs in the
system (I have to admit that the name of GICC in ACPI is confusing).

Thanks
Hanjun

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