On 11/25/2013 08:30 AM, Matthew Garrett wrote:
On Mon, Nov 25, 2013 at 05:10:46AM +0000, Zheng, Lv wrote:
From: linux-acpi-owner@xxxxxxxxxxxxxxx [mailto:linux-acpi-owner@xxxxxxxxxxxxxxx] On Behalf Of Matthew Garrett
Ugh. Really? People have been fairly careful about making sure that the
x86 SoC code is selected correctly at runtime, and losing that because
ACPICA is broken would be a shame. I think this is something that needs
to support runtime switching even if there's also support for building
kernels that only implement the reduced hardware profile.
If my reading is correct, do you mean x86 SoCs should have already tested the code.
I don't know if anyone has deployed x86 SoCs with reduced hardware yet,
but it seems like something that might happen.
So if ARM need ACPI_REDUCED_HARDWARE to be defined, the <include/acpi/platform/aclinux.h> should have lines like:
#ifdef CONFIG_ARCH_IS_ACPI_REDUCED_HARDWARE
#define ACPI_REDUCED_HARDWARE TRUE
#endif
And ARCH_IS_ACPI_REDUCED_HARDWARE should only be selected by CONFIG_ARM.
Is ACPI_REDUCED_HARDWARE supposed to indicate support for the reduced
hardware profile, or that the platform *only* implements the reduced
hardware profile?
From what I can see in ACPICA, ACPI_REDUCED_HARDWARE indicates the
platform *only* implements the reduced hardware profile. This *seems*
to be consistent with the specification -- see 3.11.1, second bullet,
for example:
Boot in ACPI mode only (ACPI Enable, ACPI Disable, SMI_CMD and
Legacy mode are not supported)
...if by "not supported" one takes that to mean "does not exist when
compiled." I can look at the ACPICA code again, just the same; perhaps
there is some reasonable way to at least select one or the other at boot
as the first step, and then allow switching between modes as a later
step.
To Lv's point, since hardware reduced mode was added in ACPI 5.0, I
don't think there has been a lot of exposure to it, especially on
working platforms on the Linux side, so I doubt there has been any
significant Linux testing of it until now.
--
ciao,
al
-----------------------------------
Al Stone
Software Engineer
Linaro Enterprise Group
al.stone@xxxxxxxxxx
-----------------------------------
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