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:

quoted

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@linaro.org>
+ *   Author: Graeme Gregory <graeme.gregory@linaro.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.