Received: by 2002:a25:8b91:0:0:0:0:0 with SMTP id j17csp468746ybl; Tue, 7 Jan 2020 09:14:14 -0800 (PST) X-Google-Smtp-Source: APXvYqz0DN26PafP3Kjly0cnlOgdhcsV8+7l06Nk3GyQDQH6zNPWRJGd+zxDVdZUibCl6rAzqizQ X-Received: by 2002:a05:6830:2361:: with SMTP id r1mr812522oth.88.1578417254609; Tue, 07 Jan 2020 09:14:14 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1578417254; cv=none; d=google.com; s=arc-20160816; b=YHJyVNA+w2kpQIjg+ycNaEt02ySPms9N1OyGDmfAX6ARLK8bdcjcNkMdg0NHyKCzOh GaUbECwFr1KzpHkQnVpOoRFm7nqTETfc1ve0Z7WoXgG6L9TIVuH6+SEVkmu87Arr0iAz 4yg1iQKzN7IrxuiTMpX/2JeGisivHBi5HkfzDkU/tnMBv83TeTM2buyTPft+CjDm3giZ 2holf+iG/3PV1zr7v0s+An1u+YP10sfy7DFQf5MtNbdx9osJZ+catoyDQVVnE5TJOtue V9YgHJ7myb2fQ9vhYvCa3UTvo4J+blZLe+0M/dkqa9FRJA59IfCLTXZoDl0oUEu4ZoVW zB0g== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:content-transfer-encoding :content-language:in-reply-to:mime-version:user-agent:date :message-id:from:references:cc:to:subject:dkim-signature; bh=b6uJhncOje5k5j8JgdUT1915LVoXHzLCLy0HXT+ESDM=; b=V05if1sC4fsY6IZf15smjYAxltiUnSQ1FjlL1A8GXeZniz32Hoc/5xiwTwXldiyNa2 Frl1Q4uozDm+zb/ihg/kfFWa7QqaVl6MdzWrLIGZpH1edvUhNvuVT+cBSHme5MD21kRm cxH/si3213UJaBeaIDxVs9azVLEzSb4C0NDbQvJWEGq2qZBhkGf2hutktOH+bbLwIQ+J uWzUlh7k5ZprtzQZgQdh3LgFVVRwzHGdTL0UfnYDmxnUN7YO+OAhhu/O4nWQ2ON4qFf+ c4hgRLqtgVcwxMLj+h9Z7NjjW/EeoygwjJIfsBXJZw6g0dQtUG7j/QwJ7dQVgeZ/d0cg BPcw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=eQMxTCND; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id y8si183828otg.309.2020.01.07.09.14.02; Tue, 07 Jan 2020 09:14:14 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=eQMxTCND; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728367AbgAGRMv (ORCPT + 99 others); Tue, 7 Jan 2020 12:12:51 -0500 Received: from mail-lf1-f65.google.com ([209.85.167.65]:45482 "EHLO mail-lf1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728211AbgAGRMu (ORCPT ); Tue, 7 Jan 2020 12:12:50 -0500 Received: by mail-lf1-f65.google.com with SMTP id 203so242380lfa.12; Tue, 07 Jan 2020 09:12:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=b6uJhncOje5k5j8JgdUT1915LVoXHzLCLy0HXT+ESDM=; b=eQMxTCNDkkImyT+meRspXjEYMXtYGwHD7PHKqBo5qAwqFLLVzwJUONW9pfx3FCT4Sa WaXhx149BGna7obIB2c2YwTzRvDksikbr4O+G2Ejom7S9a7Fl1DCA/HRL/ZhJmdFZHb3 nD05sPWfvpx+voYWKVlj0olYdVhSJARwZPr26OC7QphjWTDyAT2YLdp6q2fBwlA8K9vu E9Ap1tyCrTxBSK+oQOzHUxQ52jsVT2sZppUcK38j1x1f0pMULVnoEtRdSZhUz3sFhJCh w3t35zT5KWh2w0qQL5CmP83ncs4/hUrEdmjmjJgSCn1Uv+Q6j5Sh6JS7rpNcjfrLN70g ruKA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=b6uJhncOje5k5j8JgdUT1915LVoXHzLCLy0HXT+ESDM=; b=U9rX/VVoDIShLuGSEJqL6sfQLlF6eHRZx3Dt7I9+cHBhMwXYEr9QCUjnbz9WyfK2wQ lsp9CpdFCgScLn333WqGTolE7xlj8C6eeeSLKZ6ohnkkJ0B3bpzfpyeQiFho9ccHy3m4 3FN6hwKw+2zJ/Ls/D3sMgTFZv/cuGKJdvsLpHhcZoqRFcd78FUCXgFDkBsyS/eA1hnmX u7SiGjRjWywIDIH5ww67dOxqqg1pEtobaJw+/58LZLWE3RXqisNo7eVS5fTsnuzD5kTo Fek/qvc3Wsh+6z0sJc5vC90mjfPi2JnxA1tNBiw+tsxQLMhszTL3QzsDbsLAnkXJe4Ce aXLg== X-Gm-Message-State: APjAAAVuIEUTtbWDSKuGZeC7Ax8MBQjwqDr105cSAt1hY4BSs0esainQ rAQc8/yBbb0bA2FtBmIpJHQF4vQu X-Received: by 2002:ac2:5468:: with SMTP id e8mr273096lfn.113.1578417167078; Tue, 07 Jan 2020 09:12:47 -0800 (PST) Received: from [192.168.2.145] (79-139-233-37.dynamic.spd-mgts.ru. [79.139.233.37]) by smtp.googlemail.com with ESMTPSA id i4sm134431lji.0.2020.01.07.09.12.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 07 Jan 2020 09:12:45 -0800 (PST) Subject: Re: [PATCH v3 09/13] dmaengine: tegra-apb: Remove runtime PM usage To: Jon Hunter , Laxman Dewangan , Vinod Koul , Dan Williams , Thierry Reding , =?UTF-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= Cc: dmaengine@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org References: <20200106011708.7463-1-digetx@gmail.com> <20200106011708.7463-10-digetx@gmail.com> From: Dmitry Osipenko Message-ID: Date: Tue, 7 Jan 2020 20:12:45 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Jon, 07.01.2020 18:13, Jon Hunter пишет: > > On 06/01/2020 01:17, Dmitry Osipenko wrote: >> There is no benefit from runtime PM usage for the APB DMA driver because >> it enables clock at the time of channel's allocation and thus clock stays >> enabled all the time in practice, secondly there is benefit from manually >> disabled clock because hardware auto-gates it during idle by itself. > > This assumes that the channel is allocated during a driver > initialisation. That may not always be the case. I believe audio is one > case where channels are requested at the start of audio playback. At least serial, I2C, SPI and T20 FUSE are permanently keeping channels allocated, thus audio is an exception here. I don't think that it's practical to assume that there is a real-world use-case where audio driver is the only active DMA client. The benefits of gating the DMA clock are also dim, do you have any power-consumption numbers that show that it's really worth to care about the clock-gating?