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 <kliu5@xxxxxxxxxxx> Thanks, pushed to mmc-next for 3.10. - Chris. -- Chris Ball <cjb@xxxxxxxxxx> <http://printf.net/> One Laptop Per Child -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
