On Fri, Aug 30, 2013 at 11:20:42AM +0100, Amit Kucheria wrote:
On Fri, Aug 30, 2013 at 3:37 PM, Leo Yan leoy@marvell.com wrote:
On 08/30/2013 05:32 PM, Amit Kucheria wrote:
On Fri, Aug 30, 2013 at 2:36 PM, Leo Yan leoy@marvell.com wrote:
For later ARMv8's big.LITTLE and for current ARM64 multi-core's power management, actually we can use MCPM as well, so we want to confirm if there have plan to support MCPM framework for ARM64 as well?
An MCPM port to ARM64 is still being discussed. ARM expects PSCI to provide the necessary callbacks in firmware for ARM64. I've cc'ed Charles who is coordinating this from ARM.
hi Amit,
Thx for quick response.
I want to confirm: if use PSCI, then the core's state machine will be maintained in PSCI rather than in kernel, right? If so, then ARM will suggest ARM64 to use PSCI as the default option for power management?
That is correct.
Though PSCI's firmware will let the kernel code to be clean, but MCPM have one obvious benefit is we can maintain the code in kernel rather than in a dedicated firmware, and it's quite similar with our previous implementation for power management.
Yes, that is what the discussion is about. :) There is also the question of schedules.
One approach might be to have a light-weight PSCI backend for MCPM in the kernel that allows us to directly call PSCI instead of using MCPM heuristics. I'll let someone from ARM state their position here.
My position for the arm64 kernel support is to use the PSCI and implement the cluster power synchronisation in the firmware. IOW, no MCPM in the arm64 kernel :(. To help with this, ARM is going to provide a generic firmware implementation that SoC vendors can expand for their needs.
I am open for discussing a common API that could be shared between MCPM-based code and the PSCI one. But I'm definitely not opting for a light-weight PSCI back-end to a heavy-weight MCPM implementation.
Also note that IKS won't be supported on arm64.