On Tue, Sep 09, 2014 at 05:41:51PM +0100, Jon Masters wrote: > On 09/09/2014 12:26 PM, 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@xxxxxxxxxx> > >> + * Author: Graeme Gregory <graeme.gregory@xxxxxxxxxx> > >> + * > >> + * 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? 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. > > That specific cache behavior is a part of e.g. ACPI C3 state support > (e.g. ACPI5.1 8.1.4 Processor Power State C3). Per table 5-35, if neither WBINVD or WBINVD_FLUSH are set in the FADT, we don't get S1, S2, or S3 states either. > As you note, it's not going to work on 64-bit ARM as it does on x86, > but it's optional to implement C3 and early 64-bit ARM systems should > not report Wbindv flags in the FADT anyway. Unless the arm cache architecture changes, I wouldn't expect any 64-bit ARM system to set either of the WBINVD flags. > They can also set FADT.P_LVL3_LAT > 1000, which has the effect of > disabling C3 support, while also allowing for use of _CST objects to > define more flexible C-States later on. It sounds like we should be sanity checking these in the arm64 ACPI code for the moment. I don't want us to discover that current platforms report the wrong thing only when new platforms come out that might actually report things correctly. Mark. -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
