On 25 August 2015 at 20:24, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote: > On Wednesday, August 05, 2015 09:40:23 AM Ashwin Chaugule wrote: >> CPPC: >> ==== >> >> CPPC (Collaborative Processor Performance Control) is a new way to control CPU >> performance using an abstract continous scale as against a discretized P-state scale >> which is tied to CPU frequency only. It is defined in the ACPI 5.0+ spec. In brief, >> the basic operation involves: >> - OS makes a CPU performance request. (Can provide min and max tolerable bounds) >> >> - Platform (such as BMC) is free to optimize request within requested bounds depending >> on power/thermal budgets etc. >> >> - Platform conveys its decision back to OS >> >> The communication between OS and platform occurs through another medium called (PCC) >> Platform communication Channel. This is a generic mailbox like mechanism which includes >> doorbell semantics to indicate register updates. See drivers/mailbox/pcc.c >> >> This patchset introduces a CPPC based CPUFreq driver that works with existing governors >> such as ondemand. The CPPC table parsing and the CPPC communication semantics are >> abstracted into separate files to allow future CPPC based drivers to implement their >> own governors if required. >> >> Initial patchsets included an adaptation of the PID governor from intel_pstate.c. However >> recent experiments led to extensive modifications of the algorithm to calculate CPU >> busyness. Until it is verified that these changes are worthwhile, the existing governors >> should provide for a good enough starting point for ARM64 servers. >> >> Finer details about the PCC and CPPC spec are available in the latest ACPI 5.1 >> specification.[2] >> >> Testing: >> ======= >> >> This was tested on an SBSA compatible ARMv8 server with CPPCv2 >> firmware running on a remote processor. I verified that each CPUs >> performance limits were detected and that new performance requests >> were made by the on-demand governor proportional to the load on each >> CPU. I also verified that using the acpi_processor driver correctly >> maps the physical CPU ids to logical CPU ids, which helps in picking >> up the proper _CPC details from a processor object, in the case where >> CPU physical ids may not be contiguous. >> >> Changes since V7: >> - Simplied new kconfig options for PSS and idle. >> - Separated patch to enable acpi processor on ARM64. >> - Removed redundant kconfig cross deps on PCC. >> - Decoupled processor_perflib from new PSS kconfig option. >> >> Changes since V6: >> - Separated PSS and CST from ACPI processor driver in two patches. >> - Made new Kconfig symbols auto selectable from Arch Kconfigs. >> >> Changes since V5: >> - Checkpatch cleanups. >> - Change pss_init to pss_perf_init. Rec by Srinivas Pandruvada. >> - Explicit comment explaining why postcore_initcall to pcc mailbox. >> - Fold acpi_processor_syscore_init/exit into CONFIG_ACPI_CST. >> - Added patch with dummy functions used by ACPI_HOTPLUG_CPU. >> >> Changes since V4: >> - Misc cleanups. Addressed feedback from Rafael. >> - Made acpi_processor.c independent of C-states, P-states and others. >> - Per CPU scanning for _CPC is now made from acpi_processor.c >> - Added new Kconfig options for legacy C states and P states to enable future >> support for newer alternatives as defined in the ACPI spec 6.0. >> >> Changes since V3: >> - Split CPPC backend methods into separate files. >> - Add frontend driver which plugs into existing CPUfreq governors. >> - Simplify PCC driver by moving communication space mapping and read/write >> into client drivers. >> >> 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. >> >> Changes since V1: >> - Create a new driver based on Dirks suggestion. >> - Fold in CPPC backend hooks into main driver. >> >> Changes since V0: [1] >> - Split intel_pstate.c into a generic PID governor and platform specific backend. >> - Add CPPC accessors as PID backend. >> >> [1] - http://lwn.net/Articles/608715/ >> [2] - http://www.uefi.org/sites/default/files/resources/ACPI_5_1release.pdf >> [3] - https://patches.linaro.org/40705/ >> >> >> Ashwin Chaugule (9): >> PCC: Initialize PCC Mailbox earlier at boot >> ACPI: Split out ACPI PSS from ACPI Processor driver >> ACPI: Decouple ACPI idle and ACPI processor drivers >> ACPI: Introduce CPU performance controls using CPPC >> CPPC: Add a CPUFreq driver for use with CPPC >> ACPI: Add weak routines for ACPI CPU Hotplug >> CPPC: Probe for CPPC tables for each ACPI Processor object >> PCC: Disable compilation by default >> ACPI: Allow selection of the ACPI processor driver for ARM64 > > I've queued up [1-3/9] for 4.3, but I still have a couple of questions/comments > regarding [4/9] and the rest of the series (I'll respond to the patch messages > with those). Thanks! Would you mind taking [8/9] too? It just defaults PCC to disabled. Cheers, Ashwin. -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
