Hi,
Apologies for the late reply.
On Fri, Jun 27, 2014 at 05:44:05PM +0100, Tom Rini wrote:
On Fri, Jun 27, 2014 at 09:11:39AM -0700, York Sun wrote:
Dear Albert, Wolfgang, Tom,
I have seen some patches for PSCI. We don't have PSCI enabled on Freescale ARMv8 SoCs. Will spin-table patches be acceptable?
Baring some technical reasons why no, you can't do that, yes, lets see the patches :)
I'd point out that it's decidedly sub-optimal as spin-table provides no provision for CPU hotplug (which for Linux will affect kexec and other features relying on CPU hotplug support).
Additionally, spin-table has the unfortunate property of allowing the firmware to throw an unbound number of CPUs into the kernel at once (when they share a cpu-release-addr), where they can spend a lot of time spinning pointlessly (executing kernel code from memory and possibly fetching it into I-caches) depending on the number of events a CPU happens to generate at runtime.
Linux will continue to support spin-table, but it's far preferable to use PSCI.
Another possibility raised was trying to fix spin-table to provide provisions for CPU hotplug, but I've not had the time to look into this in great detail.
A while ago there were some PSCI patches for (32-bit) ARM [1]...
Thanks, Mark.
[1] https://git.kernel.org/cgit/linux/kernel/git/maz/u-boot.git/log/?h=wip/psci-...