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=-3.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_GIT 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 58C4DC04AB4 for ; Fri, 17 May 2019 15:35:34 +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 2BB692087E for ; Fri, 17 May 2019 15:35:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="bxglNi/D" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2BB692087E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.de 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-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-Id:Date:Subject:To :From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References: List-Owner; bh=BgQj3tX2/xyGZauhyDvcpTkMC841dcooXbK+np8yZXs=; b=bxglNi/D9OAQcB dZR497O3CPF04IF8qjWLrviDKfR8877C95iT8z26ne2QLuNo/mm2M5UarzBcMCw7C3J+6luD0qAQR wd8HBPE2k80MwgJOU33QMr70RO+bl2U+3YNiqV/kNNRG/+YB/D58PhtNnZBVcMXWfPhcLUdSyAy7e aiPjwhBgOPDkrQp6vsoNoncv/wFmiLOAsWJFmq447QOCnRXEFodmghWzUA3Lb9atgFMLTsKJYLIG7 3aHH/sW7MLTYjuy+L80WNCjf3Lzm3tISi/9QaVuIwQLHP2Sdpl3WRHWe/7QTbnLxUg1PpkSk7nPuA IsgPBVTZPwH1WzTL4Ryg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hRetL-0008CR-Ey; Fri, 17 May 2019 15:35:27 +0000 Received: from mx2.suse.de ([195.135.220.15] helo=mx1.suse.de) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1hRetB-00081M-0e; Fri, 17 May 2019 15:35:18 +0000 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id ABC58ACEF; Fri, 17 May 2019 15:35:13 +0000 (UTC) From: Nicolas Saenz Julienne To: 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 Subject: [RFC 0/5] cpufreq support for the Raspberry Pi Date: Fri, 17 May 2019 17:35:02 +0200 Message-Id: <20190517153508.18314-1-nsaenzjulienne@suse.de> X-Mailer: git-send-email 2.21.0 MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190517_083517_205394_AB7AE796 X-CRM114-Status: GOOD ( 16.76 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: f.fainelli@gmail.com, ptesarik@suse.com, sboyd@kernel.org, viresh.kumar@linaro.org, rjw@rjwysocki.net, linux-kernel@vger.kernel.org, eric@anholt.net, bcm-kernel-feedback-list@broadcom.com, Nicolas Saenz Julienne , linux-clk@vger.kernel.org, mbrugger@suse.de Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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. That's all, kind regards, Nicolas [1] https://lists.infradead.org/pipermail/linux-rpi-kernel/2019-April/008634.html [2] https://www.spinics.net/lists/linux-clk/msg36937.html --- Nicolas Saenz Julienne (5): clk: bcm2835: set CLK_GET_RATE_NOCACHE on CPU clocks clk: bcm2835: set pllb_arm divisor as readonly clk: bcm2835: use firmware interface to update pllb dts: bcm2837: add per-cpu clock devices cpufreq: add driver for Raspbery Pi arch/arm/boot/dts/bcm2837.dtsi | 8 + drivers/clk/bcm/clk-bcm2835.c | 284 ++++++++++++++++++++++++-- drivers/cpufreq/Kconfig.arm | 8 + drivers/cpufreq/Makefile | 1 + drivers/cpufreq/raspberrypi-cpufreq.c | 79 +++++++ 5 files changed, 362 insertions(+), 18 deletions(-) create mode 100644 drivers/cpufreq/raspberrypi-cpufreq.c -- 2.21.0 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel