From mboxrd@z Thu Jan 1 00:00:00 1970 From: Al Stone Subject: Re: [Linaro-acpi] [PATCH v5 0/6] CPUFreq driver using CPPC methods Date: Tue, 26 May 2015 11:23:22 -0600 Message-ID: <5564AC0A.2050501@linaro.org> References: <1432590581-8925-1-git-send-email-ashwin.chaugule@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: Received: from mail-ig0-f170.google.com ([209.85.213.170]:34886 "EHLO mail-ig0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752631AbbEZRXZ (ORCPT ); Tue, 26 May 2015 13:23:25 -0400 Received: by igbyr2 with SMTP id yr2so64147612igb.0 for ; Tue, 26 May 2015 10:23:25 -0700 (PDT) In-Reply-To: <1432590581-8925-1-git-send-email-ashwin.chaugule@linaro.org> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Ashwin Chaugule , rjw@rjwysocki.net Cc: linaro-acpi@lists.linaro.org, viresh.kumar@linaro.org, linux-pm@vger.kernel.org, patches@linaro.org, jaswinder.singh@linaro.org, sudeep.holla@arm.com On 05/25/2015 03:49 PM, 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] > > 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 (6): > PCC: Initialize PCC Mailbox earlier at boot > ACPI: Make ACPI processor driver more extensible > ACPI: Introduce CPU performance controls using CPPC > CPPC: Add a CPUFreq driver for use with CPPC > CPPC: Probe for CPPC tables for each ACPI Processor object > PCC: Enable PCC only when needed > > drivers/acpi/Kconfig | 58 ++- > drivers/acpi/Makefile | 8 +- > drivers/acpi/cppc_acpi.c | 808 ++++++++++++++++++++++++++++++++++++++++ > drivers/acpi/processor_driver.c | 89 +++-- > drivers/cpufreq/Kconfig | 2 +- > drivers/cpufreq/Kconfig.arm | 16 + > drivers/cpufreq/Kconfig.x86 | 2 + > drivers/cpufreq/Makefile | 2 + > drivers/cpufreq/cppc_cpufreq.c | 197 ++++++++++ > drivers/mailbox/Kconfig | 2 +- > drivers/mailbox/pcc.c | 2 +- > include/acpi/cppc_acpi.h | 137 +++++++ > include/acpi/processor.h | 118 +++++- > 13 files changed, 1380 insertions(+), 61 deletions(-) > create mode 100644 drivers/acpi/cppc_acpi.c > create mode 100644 drivers/cpufreq/cppc_cpufreq.c > create mode 100644 include/acpi/cppc_acpi.h > Apart from how the patches showed up in email :), nice work, Ashwin. Can you add a description of how you tested this, too? Other than that, Reviewed-by: Al Stone -- ciao, al ----------------------------------- Al Stone Software Engineer Linaro Enterprise Group al.stone@linaro.org -----------------------------------