Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754771Ab2JRJHr (ORCPT ); Thu, 18 Oct 2012 05:07:47 -0400 Received: from ch1ehsobe001.messaging.microsoft.com ([216.32.181.181]:42505 "EHLO ch1outboundpool.messaging.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752627Ab2JRJHp convert rfc822-to-8bit (ORCPT ); Thu, 18 Oct 2012 05:07:45 -0400 X-Forefront-Antispam-Report: CIP:70.37.183.190;KIP:(null);UIP:(null);IPV:NLI;H:mail.freescale.net;RD:none;EFVD:NLI X-SpamScore: 1 X-BigFish: VS1(zz98dIc89bh1432Id799hzz1202h1d1ah1d2ah1082kzzz2dh2a8h668h839h93fhd25he5bhf0ah107ah1288h12a5h12a9h12bdh1354h137ah13b6h1441h1155h) Message-ID: <507FC796.7060401@freescale.com> Date: Thu, 18 Oct 2012 17:10:46 +0800 From: Huang Shijie User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.24) Gecko/20111108 Fedora/3.1.16-1.fc14 Thunderbird/3.1.16 MIME-Version: 1.0 To: Russell King - ARM Linux CC: Vinod Koul , , , , , , , , , , , , , , , , , , , , Huang Shijie Subject: Re: [PATCH] dma: add new DMA control commands References: <1350538335-29026-1-git-send-email-b32955@freescale.com> <1350541111.5263.3.camel@vkoul-udesk3> <507FA595.4020507@freescale.com> <20121018085208.GR21164@n2100.arm.linux.org.uk> In-Reply-To: <20121018085208.GR21164@n2100.arm.linux.org.uk> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8BIT X-OriginatorOrg: freescale.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1431 Lines: 36 于 2012年10月18日 16:52, Russell King - ARM Linux 写道: > On Thu, Oct 18, 2012 at 02:45:41PM +0800, Huang Shijie wrote: >> 于 2012年10月18日 14:18, Vinod Koul 写道: >>> Why cant you do start (prepare clock etc) when you submit the descriptor >>> to dmaengine. Can be done in tx_submit callback. >>> Similarly remove the clock when dma transaction gets completed. >> I ever thought this method too. >> >> But it will become low efficient in the following case: >> >> Assuming the gpmi-nand driver has to read out 1024 pages in one >> _SINGLE_ read operation. >> The gpmi-nand will submit the descriptor to dmaengine per page. So with >> your method, >> the system will repeat the enable/disable dma clock 1024 time. At every >> enable/disable dma clock, >> the system has to enable the clock chain and it's parents ... > And what if you stop using clk_prepare_enable(), and prepare the clock > when the channel is requested and only use clk_enable() in the tx_submit yes. it's a little better. There is nearly no difference between the clk_prepare_enable() and clk_enable() in actually. the clk_gate2_ops does not have any @->prepare. thanks Huang Shijie > method? > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/