From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Ball Subject: Re: [PATCH v7 1/2] mmc: core: enhance card removal judgement for slow removal Date: Fri, 22 Mar 2013 12:21:45 -0400 Message-ID: <87k3ozpfqe.fsf@octavius.laptop.org> References: <1362036569-14364-1-git-send-email-kliu5@marvell.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: Received: from void.printf.net ([89.145.121.20]:49499 "EHLO void.printf.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933862Ab3CVQWP (ORCPT ); Fri, 22 Mar 2013 12:22:15 -0400 In-Reply-To: <1362036569-14364-1-git-send-email-kliu5@marvell.com> (Kevin Liu's message of "Thu, 28 Feb 2013 15:29:29 +0800") Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: Kevin Liu Cc: linux-mmc@vger.kernel.org, Guennadi Liakhovetski , Sujit Reddy Thumma , Jaehoon Chung , Aaron Lu , Ulf Hansson , Wei WANG , Fabio Estevam , Stephen Warren , Adrian Hunter , Philip Rakity , Shawn Guo , Johan Rudholm , Girish K S , Haijun Zhang , Zhangfei Gao , Haojian Zhuang , Chao Xie , Kevin Liu Hi, On Thu, Feb 28 2013, Kevin Liu wrote: > Function _mmc_detect_card_removed will be called to know whether > the card is still present when host->bus_ops->detect is called. > In current code, the return value of this function generally only > depend on the result of sending cmd13 to card, which may not safe > for card with detection support like slot gpio detection. > Because the communication status between host and card may out of > sync with the detect status if remove the card slowly or hands shake > during the process. The direct reason is the async between card > detect switch and card/slot pad contaction in hardware, which is > defined by spec. > > The spec define card insert/remove sequence as below (both standard size > SD card and MicroSD card have the same sequence): > "Part 1 Standard Size SD Card Mechanical Addendum Ver4.00 Final, > Appendix C: Card Detection Switch" (Take normally open type as example) > a)SD card insertion sequence: > The card detection switch should be turned on after all SD card > contact pads are connected to the host connector contact pads. > b)SD removal sequence: > The card detection switch should be turned off when the SD card > is just going to be removed and before any SD card contact pad is > disconnected from the host connector contact pad. > > Below is the sequence when this issue occur (Take slot gpio detection > as example and remove the card slowly during the process): > 1. gpio level changed and card detect interrupt triggered. > 2. mmc_rescan was launched. > 3. the card pads were still contacted with the slot pads because of slow > removal. So _mmc_detect_card_removed and mmc_rescan think card was > still present (cmd13 succeed). > 4. card pads were discontacted from the card slot pads. > So the card was actually removed finally but the card removal event > has been missed by system. > The interval length between step 1 and step 4 depends on the > card removal speed. If it's longer than the detect work schedule > delay which is 200ms, this issue will likely happen. > > This patch add the card detect status check in function > _mmc_detect_card_removed if cmd13 check succeed and host->ops->get_cd > provided. If get_cd detect no card present then schedule another detect > work 200ms later. > > Signed-off-by: Kevin Liu Thanks, pushed to mmc-next for 3.10. - Chris. -- Chris Ball One Laptop Per Child