linux-kernel - Re: [PATCH 04/19] ARM64 / ACPI: Introduce arch_fix_phys_package

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Date:	Fri, 01 Aug 2014 14:35:25 +0800
From:	Hanjun Guo <hanjun.guo@...aro.org>
To:	Sudeep Holla <sudeep.holla@....com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Mark Rutland <Mark.Rutland@....com>
CC:	"graeme.gregory@...aro.org" <graeme.gregory@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	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>,
	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>
Subject: Re: [PATCH 04/19] ARM64 / ACPI: Introduce arch_fix_phys_package_id()
 for cpu topology

On 2014-7-29 2:51, Sudeep Holla wrote:
> On 24/07/14 14:00, Hanjun Guo wrote:
>> arch_fix_phys_package_id() will be called in ACPI core to use
>> the slot number provided by ACPI to update the physical package
>> id, then we can get the right value in the "physical id" field
>> of /proc/cpuinfo.
>>
>> Signed-off-by: Hanjun Guo <hanjun.guo@...aro.org>
>> ---
>>   arch/arm64/include/asm/topology.h |    2 ++
>>   arch/arm64/kernel/topology.c      |   14 ++++++++++++++
>>   2 files changed, 16 insertions(+)
>>
>> diff --git a/arch/arm64/include/asm/topology.h
>> b/arch/arm64/include/asm/topology.h
>> index 7ebcd31..2b216d4 100644
>> --- a/arch/arm64/include/asm/topology.h
>> +++ b/arch/arm64/include/asm/topology.h
>> @@ -23,11 +23,13 @@ extern struct cpu_topology cpu_topology[NR_CPUS];
>>   void init_cpu_topology(void);
>>   void store_cpu_topology(unsigned int cpuid);
>>   const struct cpumask *cpu_coregroup_mask(int cpu);
>> +void arch_fix_phys_package_id(int num, u32 slot);
>>
>>   #else
>>
>>   static inline void init_cpu_topology(void) { }
>>   static inline void store_cpu_topology(unsigned int cpuid) { }
>> +static inline void arch_fix_phys_package_id(int num, u32 slot) { }
>>
>>   #endif
>>
>> diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
>> index 43514f9..c547885 100644
>> --- a/arch/arm64/kernel/topology.c
>> +++ b/arch/arm64/kernel/topology.c
>> @@ -281,3 +281,17 @@ void __init init_cpu_topology(void)
>>       if (parse_dt_topology())
>>           reset_cpu_topology();
>>   }
>> +
>> +/*
>> + * Use the CPU slot number provided by ACPI to update the physical
>> + * package id when cpuid_topo->cluster_id is not available, then we
>> + * can get the right value in the "physical id" field of /proc/cpuinfo.
>> + */
> 
> We don't have "physical id" field in /proc/cpuinfo on ARM64.

I'm just curious, if there are two or more CPU (SoC) chips and connected
into one system, how to tell one SoC from another?

> 
>> +void arch_fix_phys_package_id(int num, u32 slot)
>> +{
>> +    struct cpu_topology *cpuid_topo = &cpu_topology[num];
>> +
>> +    if (cpuid_topo->cluster_id == -1)
>> +        cpuid_topo->cluster_id = slot;
>> +}
>> +EXPORT_SYMBOL_GPL(arch_fix_phys_package_id);
>>
> 
> The ACPI core uses this function to set the package id as read from
> _SUN from the device. As per spec, _SUN is used by OSPM UI to identify
> slots for the user. Do we know how will this be used on ARM64 ?
> 
> If not clear at this time, better to define it or keep it empty. I see
> even x86 does nothing in that function.

I'm ok with it, will introduce a stub function for it and remove this patch.

Thanks
Hanjun


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