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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 7F245ECDE46 for ; Fri, 26 Oct 2018 15:37:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 471E42082B for ; Fri, 26 Oct 2018 15:37:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 471E42082B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=pengutronix.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727642AbeJ0APX (ORCPT ); Fri, 26 Oct 2018 20:15:23 -0400 Received: from metis.ext.pengutronix.de ([85.220.165.71]:45815 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726159AbeJ0APX (ORCPT ); Fri, 26 Oct 2018 20:15:23 -0400 Received: from kresse.hi.pengutronix.de ([2001:67c:670:100:1d::2a]) by metis.ext.pengutronix.de with esmtp (Exim 4.89) (envelope-from ) id 1gG4B8-0006VN-8S; Fri, 26 Oct 2018 17:37:38 +0200 Message-ID: <1540568255.2245.11.camel@pengutronix.de> Subject: Re: [RFC PATCH v2 01/17] OPP: Allow to request stub voltage regulators From: Lucas Stach To: Dmitry Osipenko , Viresh Kumar Cc: "Rafael J. Wysocki" , Rob Herring , Thierry Reding , Jonathan Hunter , Nishanth Menon , Stephen Boyd , Marcel Ziswiler , linux-tegra@vger.kernel.org, linux-pm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Date: Fri, 26 Oct 2018 17:37:35 +0200 In-Reply-To: References: <20181021205501.23943-1-digetx@gmail.com> <20181021205501.23943-2-digetx@gmail.com> <20181022053636.ag62j3rj3vovbz53@vireshk-i7> <20181022113224.b5fiebgy2aap66nd@vireshk-i7> <29f893be-feed-c4c5-8468-51f7228dd468@gmail.com> <20181024064123.lbpbeervghp35fe7@vireshk-i7> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6-1+deb9u1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::2a X-SA-Exim-Mail-From: l.stach@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am Freitag, den 26.10.2018, 15:03 +0300 schrieb Dmitry Osipenko: [...] > > On the other hand, the tegra20 cpufreq driver is common across a lot of boards. > > What will happen if the DT for some of the boards isn't correct and missed the > > necessary regulator node ? > > AFAIK, there is assumption that bootloader should setup regulators in > a way that kernel could work properly at max clock rates. Otherwise > things won't work. This isn't true. The assumption is that the bootloader sets up the regulators such that stable operation at the CPU speed used by the bootloader is guaranteed. Often the bootloader doesn't know about specific SKUs, so drives things at a rate/voltage that is safe across all SKUs [1], in which case the bootloader is totally unaware of the voltage needed to run the CPU at highest possible clock frequency. Regards, Lucas [1] http://git.denx.de/?p=u-boot.git;a=commit;h=2364e151e432b4ccf32dc9e6147121253d4ff86d