From patchwork Thu May 15 05:56:51 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Viresh Kumar X-Patchwork-Id: 4179271 Return-Path: X-Original-To: patchwork-linux-pm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 93ABFBFF02 for ; Thu, 15 May 2014 05:57:05 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 9E254202EB for ; Thu, 15 May 2014 05:57:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8A6A320173 for ; Thu, 15 May 2014 05:57:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753476AbaEOF5B (ORCPT ); Thu, 15 May 2014 01:57:01 -0400 Received: from mail-we0-f174.google.com ([74.125.82.174]:63031 "EHLO mail-we0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753467AbaEOF5B (ORCPT ); Thu, 15 May 2014 01:57:01 -0400 Received: by mail-we0-f174.google.com with SMTP id k48so532817wev.5 for ; Wed, 14 May 2014 22:56:59 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=wHb8tKclJFoVip4tY51Hcffi78qtm5jXEhQKHNgOpgo=; b=Mhg+MyWwwmp+77wKIjadpwyYofndGp/bJTVSXjUhYxxmD26gDnDUCzOWdFdeAHkAPj dDXDOybfDbp+1Gb0TsRiQ7EOmG1MjXVAXWLO9+tfXQlPU7buwKTK2vR5Hsc6zgdYM65A X3KVzMtmsoX6fMMW2LCwlPS4oCdQasNO/tCSFDJfayFhWG1q642/0Ig8BlykJjBcaXdY RspiEm0dQ9BBrrUiqtQb9fCoCW13XxwlTSPMTw3OoPVh4+b/p2aIDvUIYJ7EQ48yOoaV nqIfOgtPxfjxWI9gcv6+Ez8ospRGX981C8DdNzyrsKM7haSmN6EXS82DfWhUwZ/SYIB4 c1vw== X-Gm-Message-State: ALoCoQliLbq1hvaxt0kS+9tTChq4a0R0hHPGhhZU04E0I9NAJS8UIRU5sCfuQPtd2c9I9s+2MHi+ X-Received: by 10.180.36.35 with SMTP id n3mr17164266wij.23.1400133419541; Wed, 14 May 2014 22:56:59 -0700 (PDT) Received: from localhost ([213.122.173.131]) by mx.google.com with ESMTPSA id lo18sm7927711wic.1.2014.05.14.22.56.54 for (version=TLSv1.2 cipher=RC4-SHA bits=128/128); Wed, 14 May 2014 22:56:58 -0700 (PDT) From: Viresh Kumar To: rjw@rjwysocki.net Cc: linaro-kernel@lists.linaro.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, arvind.chauhan@arm.com, swarren@nvidia.com, nicolas.pitre@linaro.org, swarren@wwwdotorg.org, dianders@chromium.org, linux@arm.linux.org.uk, Viresh Kumar Subject: [RFC] cpufreq: send notifications for intermediate (stable) frequencies Date: Thu, 15 May 2014 11:26:51 +0530 Message-Id: <25738681139c04272b6d2ebeff244c6d36c893f7.1400133090.git.viresh.kumar@linaro.org> X-Mailer: git-send-email 2.0.0.rc2 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org X-Spam-Status: No, score=-7.5 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=ham 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 Douglas Anderson, recently pointed out an interesting problem due to which his udelay() was expiring earlier than it should: https://lkml.org/lkml/2014/5/13/766 While transitioning between frequencies few platforms may temporarily switch to a stable frequency, waiting for the main PLL to stabilize. For example: When we transition between very low frequencies on exynos, like between 200MHz and 300MHz, we may temporarily switch to a PLL running at 800MHz. No CPUFREQ notification is sent for that. That means there's a period of time when we're running at 800MHz but loops_per_jiffy is calibrated at between 200MHz and 300MHz. And so udelay behaves badly. To get this fixed in a generic way, lets introduce another callback safe_freq() for the cpufreq drivers. safe_freq() should return a stable intermediate frequency a platform might want to switch to, before jumping to the frequency corresponding to 'index'. Core will send the 'PRE' notification for this 'stable' frequency and 'POST' for the 'target' frequency. Though if ->target_index() fails, it will handle POST for 'stable' frequency only. Drivers must send 'POST' notification for 'stable' freq and 'PRE' for 'target' freq. If they can't switch to target frequency, they don't need to send any notification. Signed-off-by: Viresh Kumar --- Doug/Stephen, If this doesn't look too ugly, then I would need patches from you to fix your platforms as I am not well aware of clk hierarchy of your platforms. drivers/cpufreq/cpufreq.c | 13 +++++++++++-- include/linux/cpufreq.h | 18 ++++++++++++++++++ 2 files changed, 29 insertions(+), 2 deletions(-) diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index a05c921..8d1cb4f 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -1874,11 +1874,17 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy, if (notify) { freqs.old = policy->cur; - freqs.new = freq_table[index].frequency; + /* Switch to some safe intermediate freq */ + if (cpufreq_driver->safe_freq) + freqs.new = cpufreq_driver->safe_freq(policy, + index); + else + freqs.new = freq_table[index].frequency; freqs.flags = 0; pr_debug("%s: cpu: %d, oldfreq: %u, new freq: %u\n", - __func__, policy->cpu, freqs.old, freqs.new); + __func__, policy->cpu, freqs.old, + freq_table[index].frequency); cpufreq_freq_transition_begin(policy, &freqs); } @@ -1887,6 +1893,9 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy, if (retval) pr_err("%s: Failed to change cpu frequency: %d\n", __func__, retval); + else + /* Send POST notification for the target frequency */ + freqs.new = freq_table[index].frequency; if (notify) cpufreq_freq_transition_end(policy, &freqs, retval); diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h index 3f45889..b5ba275 100644 --- a/include/linux/cpufreq.h +++ b/include/linux/cpufreq.h @@ -226,6 +226,24 @@ struct cpufreq_driver { unsigned int relation); int (*target_index) (struct cpufreq_policy *policy, unsigned int index); + /* + * Only for drivers with target_index() and CPUFREQ_ASYNC_NOTIFICATION + * unset. + * + * safe_freq() should return a stable intermediate frequency a platform + * might want to switch to, before jumping to the frequency + * corresponding to 'index'. Core will send the 'PRE' notification for + * this 'stable' frequency and 'POST' for the 'target' frequency. Though + * if ->target_index() fails, it will handle POST for 'stable' frequency + * only. + * + * Drivers must send 'POST' notification for 'stable' freq and 'PRE' for + * 'target' freq. If they can't switch to target frequency, they don't + * need to send any notification. + * + */ + unsigned int (*safe_freq)(struct cpufreq_policy *policy, + unsigned int index); /* should be defined, if possible */ unsigned int (*get) (unsigned int cpu);