linux-kernel - Re: [PATCH v2 09/18] ACPI / processor: Make it possible to get CPU hardware ID via GICC

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Message-ID: <53F566B5.4060302@linaro.org>
Date:	Thu, 21 Aug 2014 11:25:41 +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>
Subject: Re: [PATCH v2 09/18] ACPI / processor: Make it possible to get CPU
 hardware ID via GICC

On 2014-8-20 22:56, Catalin Marinas wrote:
> On Tue, Aug 19, 2014 at 09:37:34AM +0100, Hanjun Guo wrote:
>> On 2014-8-18 22:27, Catalin Marinas wrote:
>>> On Mon, Aug 04, 2014 at 04:28:16PM +0100, Hanjun Guo wrote:
>>>> diff --git a/drivers/acpi/processor_core.c b/drivers/acpi/processor_core.c
>>>> index e32321c..4007313 100644
>>>> --- a/drivers/acpi/processor_core.c
>>>> +++ b/drivers/acpi/processor_core.c
>>>> @@ -64,6 +64,38 @@ static int map_lsapic_id(struct acpi_subtable_header *entry,
>>>>  	return 0;
>>>>  }
>>>>  
>>>> +/*
>>>> + * On ARM platform, MPIDR value is the hardware ID as apic ID
>>>> + * on Intel platforms
>>>> + */
>>>> +static int map_gicc_mpidr(struct acpi_subtable_header *entry,
>>>> +		int device_declaration, u32 acpi_id, int *mpidr)
>>>> +{
>>>> +	struct acpi_madt_generic_interrupt *gicc =
>>>> +	    container_of(entry, struct acpi_madt_generic_interrupt, header);
>>>> +
>>>> +	if (!(gicc->flags & ACPI_MADT_ENABLED))
>>>> +		return -ENODEV;
>>>> +
>>>> +	/* In the GIC interrupt model, logical processors are
>>>> +	 * required to have a Processor Device object in the DSDT,
>>>> +	 * so we should check device_declaration here
>>>> +	 */
>>>> +	if (device_declaration && (gicc->uid == acpi_id)) {
>>>> +		/*
>>>> +		 * Only bits [0:7] Aff0, bits [8:15] Aff1, bits [16:23] Aff2
>>>> +		 * and bits [32:39] Aff3 are meaningful, so pack the Affx
>>>> +		 * fields into a single 32 bit identifier to accommodate the
>>>> +		 * acpi processor drivers.
>>>> +		 */
>>>> +		*mpidr = ((gicc->arm_mpidr & 0xff00000000) >> 8)
>>>> +			 | gicc->arm_mpidr;
>>>
>>> You can use pack_mpidr_into_32_bits().
>>
>> processor_core.c will be used by x86 and ia64 too, it will cause
>> compile error on !ARM64 platforms.
> 
> Oh. So we do we have an ARM-specific function in core ACPI code?

Yes, GICC is ARM-specific, but all the mapping functions (get apic_id/mpidr
via acpi_id in MADT) including x86/ia64 are all there, so it's better to put it
here to keep consistency.

Thanks
Hanjun
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