On 19 November 2014 15:36, Ashwin Chaugule ashwin.chaugule@linaro.org wrote:
This patchset introduces CPPC(Collaborative Processor Performance Control) as a backend to the PID governor. The PID governor from intel_pstate.c maps cleanly onto some CPPC interfaces. e.g. The CPU performance requests are made on a continuous scale as against discrete pstate levels. The CPU performance feedback over an interval is gauged using platform specific counters which are also described by CPPC.
Although CPPC describes several other registers to provide more hints to the platform, Linux as of today does not have the infrastructure to make use of those registers. Some of the CPPC specific information could be made available from the scheduler as part of the CPUfreq and Scheduler intergration work. Until then PID can be used as the front end for CPPC.
This implementation was tested using a Thinkpad X240 Laptop which enumerates CPPC and PCC tables in its ACPI firmware.
This patchset builds on top of the PCC driver which is being reviewed separately[3].
Changes since V2:
- Select driver if !X86, since intel_pstate will use HWP extensions instead.
- Added more comments.
- Added Freq domain awareness and PSD parsing.
Apologies for resending. I had a typo in the linaro-acpi email addr.
Thanks, Ashwin