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.
Jon.