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[209.132.180.67]) by mx.google.com with ESMTP id s13si690016otd.186.2020.01.10.00.06.56; Fri, 10 Jan 2020 00:07:07 -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=@kernel.org header.s=default header.b=Yqo4FMBH; 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=kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726836AbgAJIFZ (ORCPT + 99 others); Fri, 10 Jan 2020 03:05:25 -0500 Received: from mail.kernel.org ([198.145.29.99]:34012 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726276AbgAJIFZ (ORCPT ); Fri, 10 Jan 2020 03:05:25 -0500 Received: from localhost (unknown [223.226.110.118]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9DD7120678; Fri, 10 Jan 2020 08:05:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1578643524; bh=ph4YepTwOT/qIeLabnOL4SubJAWhPNmTtBxMU/1k/JY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Yqo4FMBHCn39WlxEW1VfdmMkBx2GsMBiaRtzFJMxeAKw2mU+TFg5mK1WeMcoHqmHJ dUA0ZuEaIDxdXDeeN3L//JM+ftcjdvY0v/6u9LfMx7Kbt1HU5qj9n+UIDm11hZ2oSi ck6muWTktwT+Wjtn/i0FpdsxUAiY4bEsuRV2CGJU= Date: Fri, 10 Jan 2020 13:35:10 +0530 From: Vinod Koul To: Jon Hunter Cc: Dmitry Osipenko , Laxman Dewangan , Dan Williams , Thierry Reding , =?utf-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= , dmaengine@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 09/13] dmaengine: tegra-apb: Remove runtime PM usage Message-ID: <20200110080510.GH2818@vkoul-mobl> References: <20200106011708.7463-1-digetx@gmail.com> <20200106011708.7463-10-digetx@gmail.com> <01660250-0489-870a-6f0e-d74c5041e8e3@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <01660250-0489-870a-6f0e-d74c5041e8e3@nvidia.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07-01-20, 18:38, Jon Hunter wrote: > > On 07/01/2020 17:12, Dmitry Osipenko wrote: > > 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? > > 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. Agree, if pm is working fine with audio, doesnt make much sense to remove. Future clients or updates to existing clients can be done to make it dynamic.. -- ~Vinod