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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 6C73BC87FCB for ; Wed, 30 Jul 2025 13:36:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=YAoOGAraN2pjrqttev+Zr8SnyWszyLGEI78fJRIM/2M=; b=5B5+itBuxVlsGGUsT3teP8nlcb REYhSuZGqCxBR9r7dWcYhzB8L0VuwWiikjvWfdjGzko8Cye/Pdz/no/lwtFrYDsTFPYEAivBOMdog v2UbjTZNH7Z14VkM415SOl0U2PeHsKsIMVtNEy72ohdY18sykMhu2U55Pf/GWTuoV8aRz3XrpA3WQ /9lBIL9DIftEXYTxKfCIU0Y1Uq+K4Ro76Ji7s1IhiNCAli4LgeSIMJf1n8ZQg5oUShSLchuyB5d39 bPrNgdvvDW8ugYgN6w6xnYUdyD31z6GOr8sfZOoNeKYtfsv3mF255fkD7DPNyaBlWfyW1rKkPPUkn o9Xs2Nog==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uh6yy-00000001cWx-1cTn; Wed, 30 Jul 2025 13:36:36 +0000 Received: from ded1.1wt.eu ([163.172.96.212] helo=1wt.eu) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uh6wR-00000001cH1-3sD7; Wed, 30 Jul 2025 13:34:01 +0000 Received: (from willy@localhost) by pcw.home.local (8.15.2/8.15.2/Submit) id 56UDXhIe027054; Wed, 30 Jul 2025 15:33:43 +0200 Date: Wed, 30 Jul 2025 15:33:43 +0200 From: Willy Tarreau To: Chukun Pan Cc: alchark@gmail.com, conor+dt@kernel.org, devicetree@vger.kernel.org, heiko@sntech.de, jonas@kwiboo.se, krzk+dt@kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-rockchip@lists.infradead.org, ziyao@disroot.org Subject: Re: [PATCH v2 1/1] arm64: dts: rockchip: rk3528: Add CPU frequency scaling support Message-ID: <20250730133343.GC26787@1wt.eu> References: <20250730071145.GA26734@1wt.eu> <20250730132026.214754-1-amadeus@jmu.edu.cn> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250730132026.214754-1-amadeus@jmu.edu.cn> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250730_063400_387092_A477EA5E X-CRM114-Status: GOOD ( 21.77 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi, On Wed, Jul 30, 2025 at 09:20:26PM +0800, Chukun Pan wrote: > Hi, > > > My point is that if you disable cpufreq, the CPU is running at 1.2V, which > > is even higher. I don't know why it's running at this voltage, maybe as > > the result of initializing some regulators, but that's what we're getting. > > So the question about safety of running between 1.13-1.15 resolves to > > "it's at least safer than running without cpufreq" in the current state. > > > > And as I mentioned it's clearly linux and not u-boot that is setting 1.2V, > > because under u-boot and during kernel selection and image loading, my > > board is at 0.95V. It's only once the kernel starts to boot that it bumps > > to 1.2V. > > If opp-table is not configured, kernel will initialize the pwm-regulator > to maximum microvolts. This can be solved by configuring the pwm-regulator > in U-Boot (waiting for U-Boot to synchronize the DT of kernel 6.16): > > ``` > &vdd_arm { > regulator-init-microvolt = <953000>; > }; OK thanks for the explanation, but will be stable at highest frequency, or do we expect the TF-A or PVTM mechanism to automatically reduce the frequency enough to keep everything stable ? I'm asking because right now I'm booting at 2 GHz, and I don't imagine 2 GHz to work fine at 953mV. Also, if we'd set this to a low enough voltage that it results in throttling the CPU, it could significantly slow down the boot for no reason. If we consider that the configured max-microvolt is valid, then better continue to use it. And if it's not valid, then maybe just fix it without going full throttle to a lower value either. Just my two cents. Willy