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=-8.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,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 4C2C6C2BA83 for ; Wed, 12 Feb 2020 10:02:14 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 1F79B20675 for ; Wed, 12 Feb 2020 10:02:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="MKvKt2BS" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1F79B20675 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=hvL6nnDznU4a0yUrzugyfy+bCaZHOAoWtPjm+VUeNq8=; b=MKvKt2BSguWCnE8VeZEI4yVL5 fxsx3TNJLZv2xxS4XC8UQDbT4Tyd3luhruCRFasBShwx00N5lS8AnD2CpdauRWlZ/leaVy1in6qhN dyhkObUgQfR6GoqZ+UYE4WTQIXK/tKrA8bnBANMq66Hs9TWeOlvUnuy+zZIxikFXbTlfpECSY8DeS A2YCZq/oLqiRCFx8czTQPX2OeXgKQus7fag4CFwSuFg8sl5cSzAkbMM4lXL7pFFmzuaxk2d7/ogS8 ARGFbywvU4tJ9kV5OLYIkXSfZnCXlC7Amv69vdGB5TnfHnsG/LmGv1RMMFEgnhIfks9qEnZKSTUAv 1Z5m+2Yog==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1j1oqM-0005eQ-5b; Wed, 12 Feb 2020 10:02:06 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1j1oqJ-0005dR-2Q for linux-arm-kernel@lists.infradead.org; Wed, 12 Feb 2020 10:02:04 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 516BF30E; Wed, 12 Feb 2020 02:02:00 -0800 (PST) Received: from [10.37.12.187] (unknown [10.37.12.187]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BCACC3F68F; Wed, 12 Feb 2020 02:01:56 -0800 (PST) Subject: Re: [PATCH v3 7/7] clocksource/drivers/arm_arch_timer: validate arch_timer_rate To: Ionela Voinescu , catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, maz@kernel.org, suzuki.poulose@arm.com, sudeep.holla@arm.com, valentin.schneider@arm.com, rjw@rjwysocki.net References: <20200211184542.29585-1-ionela.voinescu@arm.com> <20200211184542.29585-8-ionela.voinescu@arm.com> From: Lukasz Luba Message-ID: <89339501-5ee4-e871-3076-c8b02c6fbf6e@arm.com> Date: Wed, 12 Feb 2020 10:01:54 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20200211184542.29585-8-ionela.voinescu@arm.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200212_020203_204901_9D63CA09 X-CRM114-Status: GOOD ( 23.79 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-doc@vger.kernel.org, peterz@infradead.org, viresh.kumar@linaro.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, mingo@redhat.com, linux-arm-kernel@lists.infradead.org Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Ionela, Valentin On 2/11/20 6:45 PM, Ionela Voinescu wrote: > From: Valentin Schneider > > Using an arch timer with a frequency of less than 1MHz can result in an > incorrect functionality of the system which assumes a reasonable rate. > > One example is the use of activity monitors for frequency invariance > which uses the rate of the arch timer as the known rate of the constant > cycle counter in computing its ratio compared to the maximum frequency > of a CPU. For arch timer frequencies less than 1MHz this ratio could > end up being 0 which is an invalid value for its use. > > Therefore, warn if the arch timer rate is below 1MHz which contravenes > the recommended architecture interval of 1 to 50MHz. > > Signed-off-by: Ionela Voinescu > Cc: Mark Rutland > Cc: Marc Zyngier > --- > drivers/clocksource/arm_arch_timer.c | 18 +++++++++++++++--- > 1 file changed, 15 insertions(+), 3 deletions(-) > > diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c > index 9a5464c625b4..4faa930eabf8 100644 > --- a/drivers/clocksource/arm_arch_timer.c > +++ b/drivers/clocksource/arm_arch_timer.c > @@ -885,6 +885,17 @@ static int arch_timer_starting_cpu(unsigned int cpu) > return 0; > } > > +static int validate_timer_rate(void) > +{ > + if (!arch_timer_rate) > + return -EINVAL; > + > + /* Arch timer frequency < 1MHz can cause trouble */ > + WARN_ON(arch_timer_rate < 1000000); I don't see a big value of having a patch just to add one extra warning, in a situation which we handle in our code with in 6/7 with: + if (!ratio) { + pr_err("System timer frequency too low.\n"); + return -EINVAL; + } Furthermore, the value '100000' here is because of our code and calculation in there, so it does not belong to arch timer. Someone might ask why it's not 200000 or a define in our header... Or questions asking why do you warn when that arch timer and cpu is not AMU capable... > + > + return 0; > +} > + > /* > * For historical reasons, when probing with DT we use whichever (non-zero) > * rate was probed first, and don't verify that others match. If the first node > @@ -900,7 +911,7 @@ static void arch_timer_of_configure_rate(u32 rate, struct device_node *np) > arch_timer_rate = rate; > > /* Check the timer frequency. */ > - if (arch_timer_rate == 0) > + if (validate_timer_rate()) > pr_warn("frequency not available\n"); > } > > @@ -1594,9 +1605,10 @@ static int __init arch_timer_acpi_init(struct acpi_table_header *table) > * CNTFRQ value. This *must* be correct. > */ > arch_timer_rate = arch_timer_get_cntfrq(); > - if (!arch_timer_rate) { > + ret = validate_timer_rate(); > + if (ret) { > pr_err(FW_BUG "frequency not available.\n"); > - return -EINVAL; > + return ret; > } > > arch_timer_uses_ppi = arch_timer_select_ppi(); > Lastly, this is arch timer. To increase chances of getting merge soon, I would recommend to drop the patch from this series. Regards, Lukasz _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel