From patchwork Fri Apr 15 22:16:34 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Al Stone X-Patchwork-Id: 8859581 Return-Path: X-Original-To: patchwork-linux-acpi@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id EF4E19F3A0 for ; Fri, 15 Apr 2016 22:16:48 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id ECAA42034A for ; Fri, 15 Apr 2016 22:16:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 51D6F20373 for ; Fri, 15 Apr 2016 22:16:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751979AbcDOWQo (ORCPT ); Fri, 15 Apr 2016 18:16:44 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51652 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751683AbcDOWQn (ORCPT ); Fri, 15 Apr 2016 18:16:43 -0400 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 46C97B0F83; Fri, 15 Apr 2016 22:16:42 +0000 (UTC) Received: from fidelio.ahs3.com ([10.3.113.3]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u3FMGf02010000; Fri, 15 Apr 2016 18:16:41 -0400 From: Al Stone To: viresh.kumar@linaro.org, rjw@rjwysocki.net Cc: lenb@kernel.org, linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, ahs3@redhat.com Subject: [PATCH] Force cppc_cpufreq to report values in KHz to fix user space reporting Date: Fri, 15 Apr 2016 16:16:34 -0600 Message-Id: <1460758594-1596-1-git-send-email-ahs3@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.24 Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org X-Spam-Status: No, score=-7.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP When CPPC is being used by ACPI on arm64, user space tools such as cpupower report CPU frequency values from sysfs that are incorrect. What the driver was doing was reporting the values given by ACPI tables in whatever scale was used to provide them. However, the ACPI spec defines the CPPC values as unitless abstract numbers. Internal kernel structures such as struct perf_cap, in contrast, expect these values to be in KHz. When these struct values get reported via sysfs, the user space tools also assume they are in KHz, causing them to report incorrect values (for example, reporting a CPU frequency of 1MHz when it should be 1.8GHz). While the investigation for a long term fix proceeds (several options are being explored, some of which may require spec changes or other much more invasive fixes), this patch forces the values read by CPPC to be read in KHz, regardless of what they actually represent. The downside is that this approach has some assumptions: (1) It relies on SMBIOS3 being used, *and* that the Max Frequency value for a processor is set to a non-zero value. (2) It assumes that all processors run at the same speed. This patch retrieves the first CPU Max Frequency from a type 4 DMI record that it can find. This may not be an issue, however, as a sampling of DMI data on x86 and arm64 indicates there is often only one such record regardless. For arm64 servers, this may be sufficient, but it does rely on firmware values being set correctly. Hence, other approaches are also being considered. This has been tested on three arm64 servers, with and without DMI, with and without CPPC support. Signed-off-by: Al Stone --- drivers/acpi/cppc_acpi.c | 61 +++++++++++++++++++++++++++++++++++++++++---- drivers/cpufreq/Kconfig.arm | 1 + 2 files changed, 57 insertions(+), 5 deletions(-) diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c index 8adac69..049dced 100644 --- a/drivers/acpi/cppc_acpi.c +++ b/drivers/acpi/cppc_acpi.c @@ -40,6 +40,9 @@ #include #include #include +#include + +#include #include /* @@ -709,6 +712,47 @@ static int cpc_write(struct cpc_reg *reg, u64 val) return ret_val; } +static u64 cppc_dmi_khz; + +static void cppc_find_dmi_mhz(const struct dmi_header *dm, void *private) +{ + u16 *mhz = (u16 *)private; + const u8 *dmi_data = (const u8 *)dm; + + if (dm->type == DMI_ENTRY_PROCESSOR && dm->length >= 48) + *mhz = (u16)get_unaligned((const u16 *)(dmi_data + 0x14)); +} + + +static u64 cppc_get_dmi_khz(void) +{ + u16 mhz; + + dmi_walk(cppc_find_dmi_mhz, &mhz); + + /* + * Real stupid fallback value, just in case there is no + * actual value set. + */ + mhz = mhz ? mhz : 1; + + return (1000 * mhz); +} + +static u64 cppc_unitless_to_khz(u64 min, u64 max, u64 val) +{ + /* + * The incoming val should be min <= val <= max. Our + * job is to convert that to KHz so it can be properly + * reported to user space via cpufreq_policy. + */ + + if (!cppc_dmi_khz) + cppc_dmi_khz = cppc_get_dmi_khz(); + + return ((val - min) * cppc_dmi_khz) / (max - min); +} + /** * cppc_get_perf_caps - Get a CPUs performance capabilities. * @cpunum: CPU from which to get capabilities info. @@ -748,17 +792,24 @@ int cppc_get_perf_caps(int cpunum, struct cppc_perf_caps *perf_caps) } } + /* + * Since these values in perf_caps will be used in setting + * up the cpufreq policy, they must always be stored in units + * of KHz. If they are not, user space tools will become very + * confused since they assume these are in KHz when reading + * sysfs. + */ cpc_read(&highest_reg->cpc_entry.reg, &high); - perf_caps->highest_perf = high; - cpc_read(&lowest_reg->cpc_entry.reg, &low); - perf_caps->lowest_perf = low; + + perf_caps->highest_perf = cppc_unitless_to_khz(low, high, high); + perf_caps->lowest_perf = cppc_unitless_to_khz(low, high, low); cpc_read(&ref_perf->cpc_entry.reg, &ref); - perf_caps->reference_perf = ref; + perf_caps->reference_perf = cppc_unitless_to_khz(low, high, ref); cpc_read(&nom_perf->cpc_entry.reg, &nom); - perf_caps->nominal_perf = nom; + perf_caps->nominal_perf = cppc_unitless_to_khz(low, high, nom); if (!ref) perf_caps->reference_perf = perf_caps->nominal_perf; diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm index 14b1f93..0573982 100644 --- a/drivers/cpufreq/Kconfig.arm +++ b/drivers/cpufreq/Kconfig.arm @@ -255,6 +255,7 @@ config ACPI_CPPC_CPUFREQ tristate "CPUFreq driver based on the ACPI CPPC spec" depends on ACPI select ACPI_CPPC_LIB + select DMI default n help This adds a CPUFreq driver which uses CPPC methods