Received: by 2002:a25:8b91:0:0:0:0:0 with SMTP id j17csp547116ybl; Tue, 7 Jan 2020 10:39:48 -0800 (PST) X-Google-Smtp-Source: APXvYqyu9WxcVc8T7DdrQX9h4u/UDvZcUhuTvP33v67xY+AWv528uRQi2cNlJwdnYVJ9Zb16CR8A X-Received: by 2002:a9d:12f1:: with SMTP id g104mr1251207otg.334.1578422388155; Tue, 07 Jan 2020 10:39:48 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1578422388; cv=none; d=google.com; s=arc-20160816; b=X0zJxHPCdIAkDjrvn55lrV8sXkroKJmeoZtjTKLd4ytV/1qIEKYryHJply5nK8V7G4 ILlOLmuHWGN/GxwQ0hML+nQpiZKKb5Ss19RpPF0e/L5M8MBjIhP/C6hTFFfE84Qipvu8 xNmbdXtyhDulb1iLrotPBPpQJHgJ2lLAduBLTtxbPawNUzrzKHNGCA7uhlpK73C0tyft p80dlskj9DoW+XNvj/l06qg0kX7BRg3coaN4aCrTcmx04cysuhaECTdJsFNGE7v70o0P Mi6DlOD07LQpCicqiAh+R98zpYeQ3ruCK7RMtN48N2tOooI4f7aOHKcls2J0YfW9yr1q DEJg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:dkim-signature:content-transfer-encoding :content-language:in-reply-to:mime-version:user-agent:date :message-id:from:references:cc:to:subject; bh=1vkKMIjMhiXQH/0LKlvaioSuV7wR0KaWYwmiXi110ng=; b=RTrm9vBlNDOZvua6eM4UVefzLpjp2sWcFBAfhmxXkT+51b31FLQCiKIQ+fXr7Q/y5Y MdGnOZnLqfw4TVWYGKfgNM44QzHTs6Lk3GIpFouhJsRyhfXJNIFWxtRkW4aTC4YFlsBf J166OE9E5ZyfQyYpDqkYgViPih0ZLqMcrQImn5jnct5mBoZ9gp9nV/yWcrjL4CftdCMC l6J63ZiBOBb9GXwFDJUN/gDb26QlKwSnyDf9Ea7gzYxl50kZeBWLH2ey9acfoC7Syd8m k56/Vlym0E34gFXb5jxvrPD+yOmlIeBjf5tWZrdasEZwsLBaRm2nZ00GmceqBMy0orz2 Lpaw== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@nvidia.com header.s=n1 header.b=JpEHXUhw; 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=NONE dis=NONE) header.from=nvidia.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id t12si337968otq.53.2020.01.07.10.39.33; Tue, 07 Jan 2020 10:39:48 -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=@nvidia.com header.s=n1 header.b=JpEHXUhw; 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=NONE dis=NONE) header.from=nvidia.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728488AbgAGSio (ORCPT + 99 others); Tue, 7 Jan 2020 13:38:44 -0500 Received: from hqnvemgate24.nvidia.com ([216.228.121.143]:15962 "EHLO hqnvemgate24.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728235AbgAGSin (ORCPT ); Tue, 7 Jan 2020 13:38:43 -0500 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate24.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Tue, 07 Jan 2020 10:37:55 -0800 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Tue, 07 Jan 2020 10:38:42 -0800 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Tue, 07 Jan 2020 10:38:42 -0800 Received: from [10.26.11.139] (10.124.1.5) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Tue, 7 Jan 2020 18:38:40 +0000 Subject: Re: [PATCH v3 09/13] dmaengine: tegra-apb: Remove runtime PM usage To: Dmitry Osipenko , Laxman Dewangan , Vinod Koul , Dan Williams , Thierry Reding , =?UTF-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= CC: , , References: <20200106011708.7463-1-digetx@gmail.com> <20200106011708.7463-10-digetx@gmail.com> From: Jon Hunter Message-ID: <01660250-0489-870a-6f0e-d74c5041e8e3@nvidia.com> Date: Tue, 7 Jan 2020 18:38:36 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL101.nvidia.com (172.20.187.10) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: quoted-printable DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1578422275; bh=1vkKMIjMhiXQH/0LKlvaioSuV7wR0KaWYwmiXi110ng=; h=X-PGP-Universal:Subject:To:CC:References:From:Message-ID:Date: User-Agent:MIME-Version:In-Reply-To:X-Originating-IP: X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=JpEHXUhwxDD57ebL8Vk3Fj6LL/ZZeLR8kkPdEbWH3mCnB2Qct+tiBOy5Hc29R4+6A UDdkbrs8GpnvjqHdr7QjBUWZJz0ZZhfL3Bo4FTgw2BlxRuoBW1bML6YjtYMyZVTebd oVz3uNg5LnikzYQNaV+u30O2HtwKRJw4F7HiUL10gv10Iwbxmk81bfsJprnlN/TZ0c 2zx+7X02oXd7CGaJ0bg/G0h4vwdwlwKAUFxNTbNWnw1eS0cqrvWtV70MmO4hD2sxP2 BpMVnSwD9T9Q9dc1g0Yibi+cc0EjJle6gVznV3x0RfZ/USMWyDa1sCd891QqWs+pjM GibEYhE7xVfmQ== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/01/2020 17:12, Dmitry Osipenko wrote: > 07.01.2020 18:13, Jon Hunter =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >> >> On 06/01/2020 01:17, Dmitry Osipenko wrote: >>> There is no benefit from runtime PM usage for the APB DMA driver becaus= e >>> it enables clock at the time of channel's allocation and thus clock sta= ys >>> enabled all the time in practice, secondly there is benefit from manual= ly >>> 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. >=20 > 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. >=20 > 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? No, but at the same time, I really don't see the point in this. In fact, I think it is a step backwards. If we wanted to only enable clocks while DMA channels are active we could. So I request you drop this. Jon --=20 nvpublic