From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752844AbaLOOxQ (ORCPT ); Mon, 15 Dec 2014 09:53:16 -0500 Received: from mailout3.w1.samsung.com ([210.118.77.13]:26832 "EHLO mailout3.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752494AbaLOOxL (ORCPT ); Mon, 15 Dec 2014 09:53:11 -0500 MIME-version: 1.0 Content-type: text/plain; charset=UTF-8 X-AuditID: cbfec7f4-b7f126d000001e9a-97-548ef5d313e2 Content-transfer-encoding: 8BIT Message-id: <1418655186.20866.5.camel@AMDC1943> Subject: Re: [RFC PATCHv3 1/7] devfreq: event: Add new devfreq_event class to provide basic data for devfreq governor From: Krzysztof Kozlowski To: Chanwoo Choi Cc: myungjoo.ham@samsung.com, kyungmin.park@samsung.com, kgene.kim@samsung.com, rafael.j.wysocki@intel.com, a.kesavan@samsung.com, tomasz.figa@gmail.com, b.zolnierkie@samsung.com, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org Date: Mon, 15 Dec 2014 15:53:06 +0100 In-reply-to: <1418372852-12454-2-git-send-email-cw00.choi@samsung.com> References: <1418372852-12454-1-git-send-email-cw00.choi@samsung.com> <1418372852-12454-2-git-send-email-cw00.choi@samsung.com> X-Mailer: Evolution 3.10.4-0ubuntu2 X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFrrJLMWRmVeSWpSXmKPExsVy+t/xK7qXv/aFGNz6amHxeM1iJouNM9az Wlz/8pzVYv6Rc6wWvQuuslmcbXrDbrHp8TVWi8u75rBZfO49wmgx4/w+JovbjSvYLB6veMtu sWrXH0YHXo+ds+6yeyze85LJY/OSeo++LasYPT5vkgtgjeKySUnNySxLLdK3S+DK+PhiNVvB d/GKB/viGhh3C3cxcnJICJhIrH90kBnCFpO4cG89WxcjF4eQwFJGiQ/NC1hBErwCghI/Jt9j 6WLk4GAWkJc4cikbJMwsoC4xad4iZoj6z4wSPWu/Q9XrS3R+mcgEYgsLlEuc+zwXLM4mYCyx efkSNhBbREBDYubfK4wgzcwC15kkei4eBGtgEVCV6Fu/BqyBU8BN4vat71AbGhkl5ty6xQ5y hYSAskRjv9sERoFZSO6bhXDfLCT3LWBkXsUomlqaXFCclJ5rqFecmFtcmpeul5yfu4kREh1f djAuPmZ1iFGAg1GJhzdhb2+IEGtiWXFl7iFGCQ5mJRHeWe/6QoR4UxIrq1KL8uOLSnNSiw8x MnFwSjUwuugZFTwLr1BhuPuoJeTOukjN3NPP9n2d0sFTPj/QTCVD8J0kp6dtQ222ciVDUyvH /6MG30K/eVZmbprcVqfs88RQqfV27eKkboEY3z73Fa29LCFq0x8VS7zkD35U1rh7S9WvhRcU OI6fi8qcfeujwqO8S+qcp7UuFm9ekv3Ib4/A64jPz04psRRnJBpqMRcVJwIAoEGosGwCAAA= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On pią, 2014-12-12 at 17:27 +0900, Chanwoo Choi wrote: > This patch add new devfreq_event class for devfreq_event device which provide > raw data (e.g., memory bus utilization/GPU utilization). This raw data from > devfreq_event data would be used for the governor of devfreq subsystem. > - devfreq_event device : Provide raw data for governor of existing devfreq device > - devfreq device : Monitor device state and change frequency/voltage of device > using the raw data from devfreq_event device > > The devfreq subsystem support generic DVFS(Dynamic Voltage/Frequency Scaling) > for Non-CPU Devices. The devfreq device would dertermine current device state > using various governor (e.g., ondemand, performance, powersave). After completed > determination of system state, devfreq device would change the frequency/voltage > of devfreq device according to the result of governor. > > But, devfreq governor must need basic data which indicates current device state. > Existing devfreq subsystem only consider devfreq device which check current system > state and determine proper system state using basic data. There is no subsystem > for device providing basic data to devfreq device. > > The devfreq subsystem must need devfreq_event device(data-provider device) for > existing devfreq device. So, this patch add new devfreq_event class for > devfreq_event device which read various basic data(e.g, memory bus utilization, > GPU utilization) and provide measured data to existing devfreq device through > standard APIs of devfreq_event class. > > The following description explains the feature of two kind of devfreq class: > - devfreq class (existing) > : devfreq consumer device use raw data from devfreq_event device for > determining proper current system state and change voltage/frequency > dynamically using various governors. > > - devfreq_event class (new) > : Provide measured raw data to devfreq device for governor > > Cc: MyungJoo Ham > Cc: Kyungmin Park > Signed-off-by: Chanwoo Choi [...] > +/** > + * devfreq_event_get_event() - Get event and total_event from devfreq-event dev. > + * @edev : the devfreq-event device > + * > + * Note that this function get the calculated event data from devfreq-event dev > + * after stoping the progress of whole sequence of devfreq-event dev. Return > + * current event data and total_event should be stored in second parameter > + * (total_event). > + */ > +u64 devfreq_event_get_event(struct devfreq_event_dev *edev, u64 *total_event) > +{ I think this function should return int (0 for success, negative otherwise) and store the "event" under pointer passed as argument. Why? Because: 1. error conditions are indicated with 'return 0' but should be 'return -EINVAL' 2. Exynos-ppmu driver returns -EINVAL. Checking for error conditions is in such case more complex than it should. Best regards, Krzysztof