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Date: Tue, 9 Sep 2014 17:54:45 +0100
From: Mark Rutland <mark.rutland@....com>
To: Catalin Marinas <Catalin.Marinas@....com>
Cc: "hanjun.guo@...aro.org" <hanjun.guo@...aro.org>,
"Rafael J. Wysocki" <rjw@...ysocki.net>,
Olof Johansson <olof@...om.net>,
"grant.likely@...aro.org" <grant.likely@...aro.org>,
"graeme.gregory@...aro.org" <graeme.gregory@...aro.org>,
Arnd Bergmann <arnd@...db.de>,
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>,
Al Stone <al.stone@...aro.org>,
Tomasz Nowicki <tomasz.nowicki@...aro.org>
Subject: Re: [PATCH v3 02/17] ARM64 / ACPI: Get RSDP and ACPI boot-time tables
On Tue, Sep 09, 2014 at 05:26:49PM +0100, Catalin Marinas wrote:
> On Mon, Sep 01, 2014 at 03:57:40PM +0100, Hanjun Guo wrote:
> > diff --git a/arch/arm64/include/asm/acenv.h b/arch/arm64/include/asm/acenv.h
> > new file mode 100644
> > index 0000000..3899ee6
> > --- /dev/null
> > +++ b/arch/arm64/include/asm/acenv.h
> > @@ -0,0 +1,18 @@
> > +/*
> > + * ARM64 specific ACPICA environments and implementation
> > + *
> > + * Copyright (C) 2014, Linaro Ltd.
> > + * Author: Hanjun Guo <hanjun.guo@...aro.org>
> > + * Author: Graeme Gregory <graeme.gregory@...aro.org>
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License version 2 as
> > + * published by the Free Software Foundation.
> > + */
> > +
> > +#ifndef _ASM_ACENV_H
> > +#define _ASM_ACENV_H
> > +
> > +#define ACPI_FLUSH_CPU_CACHE() WARN_ONCE(1, "Not currently supported on ARM64")
>
> Does this mean that it will be supported at some point?
>From what I recall it's impossible to support as we have no equivalent
of WBINVD -- the possibility migration of dirty cache lines renders it
impossible to guarantee that the caches remain empty (or that data even
left the local caches in the first place).
> Looking at the places where this function is called, I don't really
> see how this would ever work on ARM. Which means that we add such
> macro just to be able to compile code that would never be used on
> arm64. I would rather see the relevant ACPI files only compiled on
> x86/IA-64 rather than arm64.
Agreed.
It looks like include/acpi/platform/acenv.h defines an empty
ACPI_FLUSH_CPU_CACHE() stub, so something else should probably be done
to turn the use of ACPI_FLUSH_CPU_CACHE() into a build-time bug on
arm64.
Mark.
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