On Thu, Jan 09, 2014 at 09:20:23PM +0000, Al Stone wrote:
On 01/09/2014 10:38 AM, Catalin Marinas wrote:
On 8 January 2014 12:46, Arnd Bergmann arnd@arndb.de wrote:
On Wednesday 08 January 2014, al.stone@linaro.org wrote:
Even though support for X86 in hardware reduced mode is possible, it is NOT enabled. Extensive effort has gone into the Linux kernel so that there is a single kernel image than can run on all x86 hardware; the kernel changes run-time behavior to adapt to the hardware being used. This is not currently possible with the existing ACPICA infrastructure but only presents a problem on achitectures supporting both hardware-reduced and legacy modes of ACPI -- i.e., on x86 only.
Not sure about the logic here: While it's certainly possible to build a kernel that runs on all x86 machines, it's also possible to build one that only runs on some of them when some basic options are turned off. I don't see any difference between that and what we have on ARM64 or the multiplatform subset of ARM32.
Would we ever need !CONFIG_ACPI_REDUCED_HARDWARE_ONLY on ARM or ARM64? If not, we could even make this always on for these archs.
Not that I know of -- and I would hope not. This mode is so much more straightforward that it makes no sense to me to do anything but reduced HW if you have the choice.
Thanks for clarifying.
I assume you were thinking of something like this in the arch Kconfig file:
config ARM64 .... select ACPI_REDUCED_HARDWARE_ONLY if ACPI ...
But, do let me know if you had something else in mind. I think it does make sense to add so I'll put this in the next version.
The change makes sense but I think it should come with the patches for ACPI support on arm64 rather than your hw-reduced patches.