linux-kernel - Re: [PATCH v7 11/17] ACPI / processor: Make it possible to get CPU hardware ID via GICC

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Message-ID: <54BE496D.3050604@linaro.org>
Date:	Tue, 20 Jan 2015 20:26:21 +0800
From:	Hanjun Guo <hanjun.guo@...aro.org>
To:	Catalin Marinas <catalin.marinas@....com>
CC:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Olof Johansson <olof@...om.net>, Arnd Bergmann <arnd@...db.de>,
	Mark Rutland <Mark.Rutland@....com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Will Deacon <Will.Deacon@....com>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	"graeme.gregory@...aro.org" <graeme.gregory@...aro.org>,
	Sudeep Holla <Sudeep.Holla@....com>,
	"jcm@...hat.com" <jcm@...hat.com>,
	Jason Cooper <jason@...edaemon.net>,
	Marc Zyngier <Marc.Zyngier@....com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Mark Brown <broonie@...nel.org>, Rob Herring <robh@...nel.org>,
	Robert Richter <rric@...nel.org>,
	Randy Dunlap <rdunlap@...radead.org>,
	Charles Garcia-Tobin <Charles.Garcia-Tobin@....com>,
	"phoenix.liyi@...wei.com" <phoenix.liyi@...wei.com>,
	Timur Tabi <timur@...eaurora.org>,
	"suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>,
	"wangyijing@...wei.com" <wangyijing@...wei.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 v7 11/17] ACPI / processor: Make it possible to get CPU
 hardware ID via GICC

On 2015年01月20日 19:17, Catalin Marinas wrote:
> On Wed, Jan 14, 2015 at 03:04:59PM +0000, Hanjun Guo wrote:
>> --- 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;
>
> Nitpick: I would clarify the comment here since "meaningful" doesn't
> necessarily mean that the other bits are 0. And if they are not, the
> above masking is not enough. Looking at the ACPI 5.1 spec, bits other
> than Aff[0-3] must be zero.
>
> Same for the pack_mpidr() comment.

OK, how about:

/*
  * bits other than [0:7] Aff0, [8:15] Aff1, [16:23] Aff2 and
  * [32:39] Aff3 must be 0 which is defined in ACPI 5.1, so pack
  * the Affx fields into a single 32 bit identifier to accommodate
  * the acpi processor drivers.
  */

Thanks
Hanjun
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