linux-kernel - Re: [PATCH v8 11/21] ARM64 / ACPI: Get PSCI flags in FADT for PSCI init

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Date:	Thu, 05 Feb 2015 17:48:37 +0800
From:	Hanjun Guo <hanjun.guo@...aro.org>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
CC:	Catalin Marinas <Catalin.Marinas@....com>,
	"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>,
	"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>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	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>,
	Ashwin Chaugule <ashwinc@...eaurora.org>,
	"suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>,
	Mark Langsdorf <mlangsdo@...hat.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>,
	Tomasz Nowicki <tomasz.nowicki@...aro.org>
Subject: Re: [PATCH v8 11/21] ARM64 / ACPI: Get PSCI flags in FADT for PSCI
 init

On 2015年02月05日 00:43, Lorenzo Pieralisi wrote:
> On Mon, Feb 02, 2015 at 12:45:39PM +0000, Hanjun Guo wrote:
>> From: Graeme Gregory <graeme.gregory@...aro.org>
>>
>> There are two flags: PSCI_COMPLIANT and PSCI_USE_HVC. When set,
>> the former signals to the OS that the firmware is PSCI compliant.
>> The latter selects the appropriate conduit for PSCI calls by
>> toggling between Hypervisor Calls (HVC) and Secure Monitor Calls
>> (SMC).
>>
>> FADT table contains such information in ACPI 5.1, FADT table was
>> parsed in ACPI table init and copy to struct acpi_gbl_FADT, so
>> use the flags in struct acpi_gbl_FADT for PSCI init.
>
> So you do rely on a global FADT being available, if you use it for PSCI
> detection you can use it for ACPI revision detection too, right ?

Yes, I think so.

>
> Point is, either we should not use the global FADT table, or we use
> it consistently, or there is something I am unaware of that prevents
> you from using in some code paths and I would like to understand
> why.

global FADT table is initialized when parsing the tables from RSDP in
ACPICA core, and it should be work on ARM64 too.

Thanks
Hanjun
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