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=-7.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=ham 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 CB4AFC4360C for ; Fri, 27 Sep 2019 11:22:25 +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 96866217D9 for ; Fri, 27 Sep 2019 11:22:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="BRJmzR7D" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 96866217D9 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org 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:Message-ID:References:In-Reply-To:From:Date: MIME-Version:Subject:To:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=ciBj0xDw2eS5WuiKr7uRwDkQNU+CRAEzf+8xdz/1hQM=; b=BRJmzR7DDYEcQrwHke0Xi3mwu Wq4ysecjEqdDjT51L4vesuyu/xaC/Zoe+0XJo0wYkBnHQ39hkOSchjJSIayJBBfq3z7EKXA1pIrgL W4luzE8vF10ygtbh5wAM4QoHWkGtVPms+DGSIeoLqegeCim6PuiVETic0S9J0pxyCUffQEIA+7x31 dlktv4U/1sSLo7BFvEjHGdRnY/sIXPWfjd0ADAQPJWlRVJFX+jWOB66JMqJcN/HRuVm46HNWgcd84 XnGKly9qfcsAEhRY2PqH57yYxdMd7TKWeWvt2qyDZb1poUlKQVuSTG05raM1++m5thCDHx7coll1I KvP9NW6fg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.2 #3 (Red Hat Linux)) id 1iDoKO-0005jo-VS; Fri, 27 Sep 2019 11:22:24 +0000 Received: from inca-roads.misterjones.org ([213.251.177.50]) by bombadil.infradead.org with esmtps (Exim 4.92.2 #3 (Red Hat Linux)) id 1iDoKM-0005if-6g for linux-arm-kernel@lists.infradead.org; Fri, 27 Sep 2019 11:22:23 +0000 Received: from www-data by cheepnis.misterjones.org with local (Exim 4.80) (envelope-from ) id 1iDoKF-00076R-Dm; Fri, 27 Sep 2019 13:22:15 +0200 To: Benjamin Gaignard Subject: Re: [PATCH] ARM: dts: stm32: Enable high resolution timer X-PHP-Originating-Script: 0:main.inc MIME-Version: 1.0 Date: Fri, 27 Sep 2019 12:22:13 +0100 From: Marc Zyngier In-Reply-To: <20190927084819.645-1-benjamin.gaignard@st.com> References: <20190927084819.645-1-benjamin.gaignard@st.com> Message-ID: X-Sender: maz@kernel.org User-Agent: Roundcube Webmail/0.7.2 X-SA-Exim-Connect-IP: X-SA-Exim-Rcpt-To: benjamin.gaignard@st.com, alexandre.torgue@st.com, robh+dt@kernel.org, mark.rutland@arm.com, devicetree@vger.kernel.org, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on cheepnis.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190927_042222_395574_1C60896F X-CRM114-Status: GOOD ( 13.95 ) 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: mark.rutland@arm.com, devicetree@vger.kernel.org, alexandre.torgue@st.com, linux-kernel@vger.kernel.org, robh+dt@kernel.org, linux-stm32@st-md-mailman.stormreply.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 On 2019-09-27 09:48, Benjamin Gaignard wrote: > Adding always-on makes arm arch_timer claim to be an high resolution > timer. > That is possible because power mode won't stop clocking the timer. The "always-on" is not about the clock. It is about the comparator. The clock itself is *guaranteed* to always tick. If it didn't, that'd be an integration bug, and a pretty bad one. What you're claiming here is that your CPU never enters a low-power mode? Ever? I find this very hard to believe. Furthermore, claiming that always-on is the way to force the arch-timer to be an hrtimer is factually wrong. This is what happens *if* this is the only timer in the system. The only case this is true is for virtual machines. Anything else has a global timer somewhere that will allow the arch timers to be used as an hrtimer. I'm pretty sure you too have a global timer somewhere in your system. Enable it, and enjoy hrtimers without having to lie about the properties of your system! ;-) M. > > Signed-off-by: Benjamin Gaignard > --- > arch/arm/boot/dts/stm32mp157c.dtsi | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/arm/boot/dts/stm32mp157c.dtsi > b/arch/arm/boot/dts/stm32mp157c.dtsi > index 9b11654a0a39..74f64745d60d 100644 > --- a/arch/arm/boot/dts/stm32mp157c.dtsi > +++ b/arch/arm/boot/dts/stm32mp157c.dtsi > @@ -50,6 +50,7 @@ > , > ; > interrupt-parent = <&intc>; > + always-on; > }; > > clocks { -- Jazz is not dead. It just smells funny... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel