From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH 01/12] mmc: sdhci: add support for auto CMD23 Date: Fri, 18 Feb 2011 14:08:35 +0100 Message-ID: <201102181408.35946.arnd@arndb.de> References: <1297762510-2696-1-git-send-email-arindam.nath@amd.com> <201102181150.41350.arnd@arndb.de> <6C03668EAF45B747AF947A1603D1B300DCED1913@SAUSEXMBP01.amd.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: Received: from moutng.kundenserver.de ([212.227.17.8]:53626 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754836Ab1BRNXS (ORCPT ); Fri, 18 Feb 2011 08:23:18 -0500 In-Reply-To: <6C03668EAF45B747AF947A1603D1B300DCED1913@SAUSEXMBP01.amd.com> Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: "Nath, Arindam" Cc: zhangfei gao , "cjb@laptop.org" , "linux-mmc@vger.kernel.org" , "Su, Henry" , "Lu, Aaron" , "anath.amd@gmail.com" On Friday 18 February 2011, Nath, Arindam wrote: > > AFAICT, whether CMD23 can be used or not is primarily a decision based > > on > > the card, and the block driver might want issue it for a longer range > > if it needs to split a block request into multiple MMC requests. > > Thanks for the comments. Yes, whether a card supports CMD23 depends on > the card, but Auto CMD23 is a feature added to the Host Controller v3.00 > just like Auto CMD12. I am already doing a check inside > sdhci_host_auto_cmd23_supported() whether the card supports CMD23, and > whether the request is for multiple block transfers. Also I tried to make > my implementation consistent with Auto CMD12 implementation already > there in the sdhc code. Ok, I see. But, assuming that the block driver was changed to always to CMD23 where appropriate, what is the advantage auf Auto CMD23? As far as I can tell, changing the block driver would make all hosts faster, not just sdhci, and it would be able to cover the split requests I mentioned. Arnd