From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9ECB8C35646 for ; Fri, 21 Feb 2020 18:20:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 73FF8222C4 for ; Fri, 21 Feb 2020 18:20:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="XFlHOObl" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729597AbgBUSUJ (ORCPT ); Fri, 21 Feb 2020 13:20:09 -0500 Received: from mail-lf1-f65.google.com ([209.85.167.65]:40700 "EHLO mail-lf1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728759AbgBUSUJ (ORCPT ); Fri, 21 Feb 2020 13:20:09 -0500 Received: by mail-lf1-f65.google.com with SMTP id c23so2156530lfi.7; Fri, 21 Feb 2020 10:20:07 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=FUjaUqxyiUgON33VsY6WWwS4Yfhr7OqQL1lnqu5PDUo=; b=XFlHOOblbqwr7y7riUWmwEqug0A3tmqiCYT1aImiWk4YIOXEdeoD8vDRyhLvAesFbJ akRSRq4jR2D7GgD9bmsCJDojb1LogbBFiY5WDLSvOLes334uvNJB6amLH3GZPtbQjMe+ IlZt4Bn2QE0BmN1phR01KBoo1XjeBioy5KWyQpxE74izc0g7t+FJMB1ZaIfjR3cMibhI vOvYwQKz/qazCklv10E8xlMMReYXazO5IK28wAzAYEcycZcvDg76yMujWgMWo6GHFT/g Pl3AVbuCEmlMbno2SLg223SqN0wtrCwCUv0iG7F1kFFu8K/p5abwXgDxlOmsuQxqlw2X HCIg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=FUjaUqxyiUgON33VsY6WWwS4Yfhr7OqQL1lnqu5PDUo=; b=rLoQzM/9meEiikkuEcmnvjNMZBhlkwyEQLgqbIWvkXJKOnIkhp6rNNiZKNJgZ5gHfz qx7x+0R6JMZit6V3NWP/etJfpB+xjeqy8UE/VCKfx1cjV/rZ18B15vjvGCHSN5fz0Tbk 5QBuKKFmh+K4ddUzUGMdjEiEJ4fZKKQdPagXmJXdiHdoMVtDpLUjQ1DJQofto5jb3uA2 SwQz0OL6l3Qk8bVtXXPlL3GJOTtNMacPru9i6coyB5h3F+8AYHE0Hc2pFPkqrHwQY2YB pK/Sjh9O43sOTlFBFWYEiUoEYw/vIvHscduC9FElraob4wfW784hOGADqyEdLlsfJt6l k9DQ== X-Gm-Message-State: APjAAAXLQy9NQKaLEvVJZqGmMZMprn0vQnfx8g1OdzRgO2IO0iez6Ahb 4IbdRxVUyxCogJKaMhXDGh07uBlt X-Google-Smtp-Source: APXvYqyT3JSqBAYUvkzb+dwmrCpPPqoj21helZR6dyy6a3B/se73aYcbnsLf0Y0Lj0wzBasjk0VtMg== X-Received: by 2002:ac2:434f:: with SMTP id o15mr3226832lfl.86.1582309206012; Fri, 21 Feb 2020 10:20:06 -0800 (PST) Received: from [192.168.2.145] (79-139-233-37.dynamic.spd-mgts.ru. [79.139.233.37]) by smtp.googlemail.com with ESMTPSA id d26sm2037966lfa.44.2020.02.21.10.20.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 21 Feb 2020 10:20:05 -0800 (PST) Subject: Re: [PATCH v9 09/17] arm: tegra20: cpuidle: Handle case where secondary CPU hangs on entering LP2 To: Daniel Lezcano Cc: Thierry Reding , Jonathan Hunter , Peter De Schrijver , "Rafael J. Wysocki" , =?UTF-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= , Jasper Korten , David Heidelberg , Peter Geis , linux-pm@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org References: <20200212235134.12638-1-digetx@gmail.com> <20200212235134.12638-10-digetx@gmail.com> <20200221154318.GO10516@linaro.org> <239a2b66-8da8-2e6c-d19d-9ed207ad0a64@gmail.com> <20200221173649.GU10516@linaro.org> From: Dmitry Osipenko Message-ID: Date: Fri, 21 Feb 2020 21:19:59 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: <20200221173649.GU10516@linaro.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 21.02.2020 20:36, Daniel Lezcano пишет: > On Fri, Feb 21, 2020 at 07:56:51PM +0300, Dmitry Osipenko wrote: >> Hello Daniel, >> >> 21.02.2020 18:43, Daniel Lezcano пишет: >>> On Thu, Feb 13, 2020 at 02:51:26AM +0300, Dmitry Osipenko wrote: >>>> It is possible that something may go wrong with the secondary CPU, in that >>>> case it is much nicer to get a dump of the flow-controller state before >>>> hanging machine. >>>> >>>> Acked-by: Peter De Schrijver >>>> Tested-by: Peter Geis >>>> Tested-by: Jasper Korten >>>> Tested-by: David Heidelberg >>>> Signed-off-by: Dmitry Osipenko >>>> --- > > [ ... ] > >>>> +static int tegra20_wait_for_secondary_cpu_parking(void) >>>> +{ >>>> + unsigned int retries = 3; >>>> + >>>> + while (retries--) { >>>> + ktime_t timeout = ktime_add_ms(ktime_get(), 500); >>> >>> Oops I missed this one. Do not use ktime_get() in this code path, use jiffies. >> >> Could you please explain what benefits jiffies have over the ktime_get()? > > ktime_get() is very slow, jiffies is updated every tick. But how jiffies are supposed to be updated if interrupts are disabled? Aren't jiffies actually slower than ktime_get() because jiffies are updating every 10/1ms (depending on CONFIG_HZ)? We're kinda interesting here in getting into deep-idling state as quick as possible. I was checking how much time takes the busy-loop below and it takes ~40-150us in average, which is good enough. >>>> + >>>> + /* >>>> + * The primary CPU0 core shall wait for the secondaries >>>> + * shutdown in order to power-off CPU's cluster safely. >>>> + * The timeout value depends on the current CPU frequency, >>>> + * it takes about 40-150us in average and over 1000us in >>>> + * a worst case scenario. >>>> + */ >>>> + do { >>>> + if (tegra_cpu_rail_off_ready()) >>>> + return 0; >>>> + >>>> + } while (ktime_before(ktime_get(), timeout)); >>> >>> So this loop will aggresively call tegra_cpu_rail_off_ready() and retry 3 >>> times. The tegra_cpu_rail_off_ready() function can be called thoushand of times >>> here but the function will hang 1.5s :/ >>> >>> I suggest something like: >>> >>> while (retries--i && !tegra_cpu_rail_off_ready()) >>> udelay(100); >>> >>> So calls to tegra_cpu_rail_off_ready() and 100us x maximum >>> impact. >> But udelay() also results into CPU spinning in a busy-loop, and thus, >> what's the difference? > > busy looping instead of register reads with all the hardware things involved behind. Please notice that this code runs only on an older Cortex-A9/A15, which doesn't support WFE for the delaying, and thus, CPU always busy-loops inside udelay(). What about if I'll add cpu_relax() to the loop? Do you think it it could have any positive effect?