Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754570Ab2JRGma (ORCPT ); Thu, 18 Oct 2012 02:42:30 -0400 Received: from co1ehsobe003.messaging.microsoft.com ([216.32.180.186]:53890 "EHLO co1outboundpool.messaging.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751755Ab2JRGm2 convert rfc822-to-8bit (ORCPT ); Thu, 18 Oct 2012 02:42:28 -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: 3 X-BigFish: VS3(zzc89bhd799hzz1202h1d1ah1d2ah1082kzzz2dh2a8h668h839h93fhd25he5bhf0ah107ah1288h12a5h12a9h12bdh1354h137ah13b6h1441h1155h) Message-ID: <507FA595.4020507@freescale.com> Date: Thu, 18 Oct 2012 14:45:41 +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: Vinod Koul CC: , , , , , , , , , , , , , , , , , , , , 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> In-Reply-To: <1350541111.5263.3.camel@vkoul-udesk3> 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: 1047 Lines: 30 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 ... But with this patch, we only need to enable/disable dma clock one time, just at we select the nand chip. thanks Huang Shijie -- 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/