On 12/10/2013 03:49 PM, Grant Likely wrote:
Hi Hanjun,
Okay, so after talking with Al and Graeme on IRC, I think I understand
what is going on. The fact that ACPICA doesn't allow for both normal and
hardware reduced support in the same build is a very big problem.
However, it isn't a problem for ARM since we'll never support
non-hardware reduced mode. The x86 folks need to work that out when/if
they ever add support for hardware reduced mode.
So I would say the thing to do is only allow hardware reduced mode to be
enabled on ARM, and make it ultra clear in the config text that it
cannot be supported on x86 before ACPICA is fixed.
g.
Agreed. Will make it so in the next version.
On Tue, 10 Dec 2013 23:05:03 +0800, Hanjun Guo <hanjun.guo@xxxxxxxxxx> wrote:
On 2013年12月10日 20:37, Grant Likely wrote:
On Wed, 4 Dec 2013 14:22:03 -0700, al.stone@xxxxxxxxxx wrote:
From: Al Stone <al.stone@xxxxxxxxxx>
To enable the hardware reduced mode of ACPI on some platforms (such as
ARM), we need to modify the kernel code and set ACPI_REDUCED_HARDWARE
to TRUE in the ACPICA source.
This can be done more resonably by introducing a kernel config item
to enable/disable ACPI_REDUCED_HARDWARE. We can then change the kernel
config instead of having to modify the kernel source directly to enable
the reduced hardware mode of ACPI.
Lv Zheng suggested that this configuration item does not belong in ACPICA,
the upstream source for much of the ACPI internals, but rather to the
Linux kernel itself. Hence, we introduce this flag so that we can make
ACPI_REDUCED_HARDWARE configurable. For the details of the discussion,
please refer to: http://www.spinics.net/lists/linux-acpi/msg46369.html
Support for X86 in hardware reduced mode is also provided to make it
simpler to debug this mode, and to provide for probable use in such
products. Hardware reduced mode, despite the name, exists primarily
to allow newer platforms to use a much simpler form of ACPI that does
not require supporting the legacy of previous versions of the specification,
and is likely to be used more often in the near future as a result.
Signed-off-by: Hanjun Guo <hanjun.guo@xxxxxxxxxx>
Signed-off-by: Al Stone <al.stone@xxxxxxxxxx>
---
drivers/acpi/Kconfig | 8 ++++++++
include/acpi/platform/aclinux.h | 6 ++++++
2 files changed, 14 insertions(+)
diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index 5d92485..66e6bb2 100644
--- a/drivers/acpi/Kconfig
+++ b/drivers/acpi/Kconfig
@@ -343,6 +343,14 @@ config ACPI_BGRT
data from the firmware boot splash. It will appear under
/sys/firmware/acpi/bgrt/ .
+config ACPI_REDUCED_HARDWARE
+ bool "Hardware-reduced ACPI support"
+ depends on X86 || ARM || ARM64
+ help
+ This config adds support for Hardware-reduced ACPI. When this option
+ is selected, will generate a specialized version of ACPICA that ONLY
+ supports the ACPI "reduced hardware".
+
source "drivers/acpi/apei/Kconfig"
config ACPI_EXTLOG
diff --git a/include/acpi/platform/aclinux.h b/include/acpi/platform/aclinux.h
index 28f4f4d..a33f502 100644
--- a/include/acpi/platform/aclinux.h
+++ b/include/acpi/platform/aclinux.h
@@ -52,6 +52,12 @@
#ifdef __KERNEL__
+/* Compile for reduced hardware mode if requested for this kernel config */
+
+#ifdef CONFIG_ACPI_REDUCED_HARDWARE
+#define ACPI_REDUCED_HARDWARE 1
+#endif
Will this change the way ACPICA is compiled? Will it disable
non-hardware-reduced mode?
Both yes. ACPICA supports reduced hardware mode when
ACPI_REDUCED_HARWARE is TRUE at compile time. There is
no way to support both normal ACPI and hardware reduced
ACPI with single binary image for now.
If so, then this is a big problem. Enabling
the hardware reduced feature should *not* break normal ACPI usage.
It will break normal ACPI usage but it is ok I think. Since
lots of features are not supported in the hardware in hardware
reduced mode, and normal ACPI will not run probably such as
leading kernel panic when refer to some registers which are not
exist on reduced hardware, we should introduce this kernel
config and modify the ACPI drivers to avoid such failures.
Thanks
Hanjun
--
ciao,
al
-----------------------------------
Al Stone
Software Engineer
Linaro Enterprise Group
al.stone@xxxxxxxxxx
-----------------------------------
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