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=-3.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_NEOMUTT 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 4E76DC04E87 for ; Mon, 20 May 2019 10:51:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 24C062081C for ; Mon, 20 May 2019 10:51:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="kYY51UqL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732023AbfETKv4 (ORCPT ); Mon, 20 May 2019 06:51:56 -0400 Received: from mail-pl1-f195.google.com ([209.85.214.195]:43562 "EHLO mail-pl1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725601AbfETKv4 (ORCPT ); Mon, 20 May 2019 06:51:56 -0400 Received: by mail-pl1-f195.google.com with SMTP id gn7so2387382plb.10 for ; Mon, 20 May 2019 03:51:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=1YuRtghB95O7LhcsLf1/GyzlG0H9oHKpVmg43qxycAc=; b=kYY51UqLfQVqkc2pUGOEqHYiVJK7aLiK83xI/QmKPQ83rVUHjubs4HhY3WgnjPV8Ph +p6tCG9P+dJnHcchn3HiDctSF0yQA26bk8LSB219E644Gsm0Z1FLqUnsS3+r6pJNU7JM F9fLagHSp3Mz6H1zX6oNBvGJ6baL05JXajQShS4uasI188DbB4upGMpFgPkkW+o5f/bL ZE36aahLuXDGd9PJjztiqIChzQIpcJ3YH/cNwgrxJTR7413qQpHk/qUWWIKNe90WjxM9 DRjIBj6m38yHeJnptCfjNj2CpXQpeb1y+/vPkFdyv5gLFdczZtBRPIChvp1j2Pp2eUc4 ZEUw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=1YuRtghB95O7LhcsLf1/GyzlG0H9oHKpVmg43qxycAc=; b=F6WH5pvh4InO2Mx2lKvCNokVroxY95WEmiD7TEtVKLzFYcvdg/yTY7t3cyNF3Ktuyk cemOSEfCu/CEnHiL+Ff9Cksarpw7+e1lksPocm2NRK5QoqO/oBU7afYUwqvmE/VSGTXa xRLKHxh7IxhYbya9zZrR8dpJHrs7dGADjw4dOCjoxvaY2yGyD6FBBcqO22mXFHZHlVHi VZnh4UgkdgITsLEja7CgGTOjvX29y7b66cqxlUOGwZ8j1lUTywiTwRSHoXSV6ZVsEvH+ 6FBgSGKehM10Yy0+cheItG4JcZwTR4DXct+Qzq0rzmsiQPYf2o7OkQdpMJDUN9/2qxEL dqeA== X-Gm-Message-State: APjAAAX+GSCiFaa/Ga4VcpKXyqPiwfemwWVeHMs2ubUXHqa8ZENfvjyd tjO47Q/QDPjkknGCX9Ni5vta0Q== X-Google-Smtp-Source: APXvYqx2xIC25FoDnT5f3U0WxisE/vb00p1qHkPCPrdQV39EMhcy4uT+6FeiH4ZP+MSjumuKX4Eyww== X-Received: by 2002:a17:902:f20b:: with SMTP id gn11mr75087490plb.126.1558349515329; Mon, 20 May 2019 03:51:55 -0700 (PDT) Received: from localhost ([122.172.118.99]) by smtp.gmail.com with ESMTPSA id k9sm20248370pfa.180.2019.05.20.03.51.54 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 20 May 2019 03:51:54 -0700 (PDT) Date: Mon, 20 May 2019 16:21:53 +0530 From: Viresh Kumar To: Nicolas Saenz Julienne Cc: stefan.wahren@i2se.com, devicetree@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-pm@vger.kernel.org, mbrugger@suse.de, rjw@rjwysocki.net, sboyd@kernel.org, eric@anholt.net, f.fainelli@gmail.com, bcm-kernel-feedback-list@broadcom.com, ptesarik@suse.com, ssuloev@orpaltech.com, linux-clk@vger.kernel.org, mturquette@baylibre.com, linux-kernel@vger.kernel.org Subject: Re: [RFC v2 0/5] cpufreq support for the Raspberry Pi Message-ID: <20190520105153.ftlnjx7ocr2qkxhd@vireshk-i7> References: <20190520104708.11980-1-nsaenzjulienne@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190520104708.11980-1-nsaenzjulienne@suse.de> User-Agent: NeoMutt/20180716-391-311a52 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 20-05-19, 12:47, Nicolas Saenz Julienne wrote: > Hi all, > as some of you may recall I've been spending some time looking into > providing 'cpufreq' support for the Raspberry Pi platform[1]. I think > I'm close to something workable, so I'd love for you to comment on it. > > There has been some design changes since the last version. Namely the > fact that I now make sure *only* the CPU frequency is updated. The > firmware API we use has two modes, with or without turbo. Enabling turbo > implies not only scaling the CPU clock but also the VPU and other > peripheral related clocks. This is problematic as some of them are not > prepared for this kind frequency changes. I spent some time adapting the > peripheral drivers, but the result was disappointing as they poorly > support live frequency changes (which most other chips accept, think for > instance I2C and clock stretching) but also turned out hard to integrate > into the kernel. As we were planning to use 'clk_notifiers' which turns > out not to be such a good idea as it's prone to deadlocks and not > recommended by the clock maintainers[2]. It's also worth mentioning that > the foundation kernel doesn't support VPU frequency scaling either. > > With this in mind, and as suggested by clock maintainers[2], I've > decided to integrate the firmware clock interface into the bcm2835 clock > driver. This, in my opinion, provides the least friction with the > firmware and lets us write very simple and portable higher level > drivers. As I did with the 'cpufreq' driver which simply queries the max > and min frequencies available, which are configurable in the firmware, > to then trigger the generic 'cpufreq-dt'. > > In the future we could further integrate other firmware dependent clocks > into the main driver. For instance to be able to scale the VPU clock, > which should be operated through a 'devfreq' driver. > > This was tested on a RPi3b+ and if the series is well received I'll test > it further on all platforms I own. Please always supply version history on what has changed from V1. And why do you keep sending it as RFC ? Just keep the default PATCH thing, the patches are in good shape I would say. -- viresh