linux-kernel - Re: [PATCH v2 05/18] ARM64 / ACPI: Parse FADT table to get PSCI flags for PSCI init

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Message-ID: <20140819111000.GG3302@leverpostej>
Date:	Tue, 19 Aug 2014 12:10:00 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	Hanjun Guo <hanjun.guo@...aro.org>
Cc:	Catalin Marinas <Catalin.Marinas@....com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"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 05/18] ARM64 / ACPI: Parse FADT table to get PSCI
 flags for PSCI init

> >> @@ -47,6 +49,26 @@ void __init __acpi_unmap_table(char *map, unsigned long size)
> >>  	early_memunmap(map, size);
> >>  }
> >>  
> >> +static int __init acpi_parse_fadt(struct acpi_table_header *table)
> >> +{
> >> +	struct acpi_table_fadt *fadt = (struct acpi_table_fadt *)table;
> >> +
> >> +	/*
> >> +	 * Revision in table header is the FADT Major version,
> >> +	 * and there is a minor version of FADT which was introduced
> >> +	 * by ACPI 5.1, we only deal with ACPI 5.1 or higher version
> >> +	 * to get arm boot flags, or we will disable ACPI.
> >> +	 */
> >> +	if (table->revision < 5 || fadt->minor_revision < 1) {
> > 
> > If we ever get revision 6.0, this would trigger.
> 
> Yes, good catch, actually I already fixed that in my local git repo,
> 
> +       if (table->revision > 5 ||
> +           (table->revision == 5 && fadt->minor_revision >= 1)) {
> +               return 0;
> +       } else {
> +               pr_info("FADT revision is %d.%d, no PSCI support, should be 5.1
> or higher\n",
> +                       table->revision, fadt->minor_revision);
> +               disable_acpi();
> +               return -EINVAL;
> +       }

Given you return in the first path, you don't need the remaining code to
live in an else block.

Mark.
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