On 09/12/2014 04:03 PM, Graeme Gregory wrote:
On Fri, Sep 12, 2014 at 03:43:36PM -0400, Jon Masters wrote:
On 09/12/2014 10:00 AM, Hanjun Guo wrote:
From: Graeme Gregory graeme.gregory@linaro.org
ACPI 5.1 does not currently support S states for ARM64 hardware but ACPI code will call acpi_target_system_state() for device power managment, so introduce sleep-arm.c to allow other drivers to function until S states are defined.
Aside: ACPI5.1 does define the Platform Communication Channel and CPC (Collaborative Processor Performance Control). Some details need to be fleshed out there for practical 64-bit ARMv8 server systems, but the underpinnings and mechanisms are in place in the 5.1 specification that can be built upon over time to achieve practical S-State equivalence.
^ meant C/P sorry
Disagree, S-States are about going to sleep or hibernating, that is nothing to do with CPU Performance.
Correct. In replying to the above, I was thinking about power and performance management of components - CPU (C/P), and device (D) specific power/performance states - not the overall system (S) state, and I went off on a tangent. That was off-topic. For the actual topic at hand, that of global sleep, you are correct that only G0 (S0) and S5 are really defined today. Though I do think that the PCC might be used to actually implement overall system sleep state transitions later.
Jon.