On 01/11/16 03:43, Chaotian Jing wrote: > On Mon, 2016-10-31 at 15:09 +0200, Adrian Hunter wrote: >> On 27/10/16 13:04, Ulf Hansson wrote: >>> On 20 October 2016 at 09:06, Ulf Hansson <ulf.hansson@xxxxxxxxxx> wrote: >>>> On 20 October 2016 at 04:22, Chaotian Jing <chaotian.jing@xxxxxxxxxxxx> wrote: >>>>> On Wed, 2016-10-19 at 18:41 +0200, Ulf Hansson wrote: >>>>>> Adrian, Linus, >>>>>> >>>>>> Thanks for looking into this and reporting! >>>>>> >>>>>> On 18 October 2016 at 15:23, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote: >>>>>>> On 18/10/16 11:36, Linus Walleij wrote: >>>>>>>> On Mon, Oct 17, 2016 at 4:32 PM, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote: >>>>>>>> >>>>>>>>> Before this patch the eMMC is detected and all partitions enumerated >>>>>>>>> immediately, but after the patch it doesn't come up at all, except >>>>>>>>> sometimes, when it appears minutes (!) after boot, all of a sudden. >>>>>>>> >>>>>>>> FYI this is what it looks like when it eventually happens: >>>>>>>> root@msm8660:/ [ 627.710175] mmc0: new high speed MMC card at address 0001 >>>>>>>> [ 627.711641] mmcblk0: mmc0:0001 SEM04G 3.69 GiB >>>>>>>> [ 627.715485] mmcblk0boot0: mmc0:0001 SEM04G partition 1 1.00 MiB >>>>>>>> [ 627.736654] mmcblk0boot1: mmc0:0001 SEM04G partition 2 1.00 MiB >>>>>>>> [ 627.747397] mmcblk0rpmb: mmc0:0001 SEM04G partition 3 128 KiB >>>>>>>> [ 627.756326] mmcblk0: p1 p2 p3 p4 < p5 p6 p7 p8 p9 p10 p11 p12 p13 >>>>>>>> p14 p15 p16 p17 p18 p19 p20 p21 > >>>>>>>> >>>>>>>> So after 627 seconds, a bit hard for users to wait this long for their >>>>>>>> root filesystem. >>>>>>> >>>>>>> If the driver does not support busy detection and the eMMC card provides >>>>>>> zero as the cmd6 generic timeout (which it may especially as cmd6 generic >>>>>>> timeout wasn't added until eMMCv4.5), then __mmc_switch() defaults to >>>>>>> waiting 10 minutes i.e. >>>>>>> >>>>>>> #define MMC_OPS_TIMEOUT_MS (10 * 60 * 1000) /* 10 minute timeout */ >>>>>> >>>>>> Urgh! Yes, I have verified that this is exactly what happens. >>>>>> >>>>>>> >>>>>>> So removal of CMD13 polling for HS mode (as per commit >>>>>>> 08573eaf1a70104f83fdbee9b84e5be03480e9ed) is going to be a problem for some >>>>>>> combinations of eMMC cards and host drivers. >>>>>> >>>>>> I was looking in the __mmc_switch() function, it's just a pain to walk >>>>>> trough it :-) So first out I decided to clean it up and factor out the >>>>>> polling parts. I will post the patches first out tomorrow morning, >>>>>> running some final test right now. >>>>>> >>>>>> Although, that of course doesn't solve our problem. As I see it we >>>>>> only have a few options here. >>>>>> >>>>>> 1) In case when cmd6 generic timeout isn't available, let's assign >>>>>> another empirically selected value. >>>>>> 2) Use a specific timeout when switching to HS mode. >>>>>> 3) Even if we deploy 1 (and 2), perhaps we still should allow polling >>>>>> with CMD13 for switching to HS mode - unless it causes issues for some >>>>>> cards/drivers combination? >>>>>> >>>>>> BTW, I already tried 2) and it indeed solves the problem, although >>>>>> depending on the selected timeout, it might delay the card detection >>>>>> to process. >>>>>> >>>>>> Thoughts? >>>>> >>>>> I just have a try of switching to HS mode with Hynix EMMC, the first >>>>> CMD13 gets response of 0x900, but the EMMC is still pull-low DAT0. so >>>>> that CMD13 cannot indicate current card status in this case. >>>> >>>> Thanks for sharing that. Okay, so clearly we have some cards that >>>> don't supports polling with CMD13 when switching to HS mode. >>>> One could of course add quirks for these kind of cards and do a fixed >>>> delay for them, but then to find out which these cards are is going to >>>> be hard. >>>> >>>> It seems like we are left with using a fixed delay. Any ideas of what >>>> such delay should be? And should we have one specific for switch to >>>> the various speed modes and a different one that overrides the CMD6 >>>> generic timout, when it doesn't exist? >>>> >>> >>> Replying to my own earlier response, as I believe the problem could >>> also be related to another old commit, see below. >>> >>> commit a27fbf2f067b0cd6f172c8b696b9a44c58bfaa7a >>> Author: Seungwon Jeon <tgih.jun@xxxxxxxxxxx> >>> Date: Wed Sep 4 21:21:05 2013 +0900 >>> >>> mmc: add ignorance case for CMD13 CRC error >>> >>> While speed mode is changed, CMD13 cannot be guaranteed. >>> According to the spec., it is not recommended to use CMD13 >>> to check the busy completion of the timing change. >>> If CMD13 is used in this case, CRC error must be ignored. >>> >>> Signed-off-by: Seungwon Jeon <tgih.jun@xxxxxxxxxxx> >>> Acked-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx> >>> Signed-off-by: Chris Ball <cjb@xxxxxxxxxx> >>> >>> >>> The intent with this commit was not really correct. We don't want to >>> ignore CRC errors, but instead we should *re-try* sending CMD13 once >>> we get a CRC error. >>> >>> Unfortunate since this commit, instead we tell the host driver to >>> *ignore* CRC errors and instead reads the status and returns 0 >>> (indicating success). In the mmc core, in __mmc_switch(), it will thus >>> parse the status reply, even for a reply that might have been received >>> with a CRC error. Not good! >> >> I agree: ignoring CRC errors and then expecting the status in the response >> to be correct doesn't make sense. >> >> However, it raises the question of what to do if there are always CRC errors >> e.g. if it only works without CRC errors once the mode and frequency are >> changed in the host controller. >> >>> I am wondering whether this actually is the main problem to why we >>> think polling isn't working for some cases. And perhaps that was the >>> original problem Chaotian was trying to solve? >>> >>> Thoughts? >> >> Does Chaotian have a real problem since his driver has busy detection anyway? > > In fact, I have not encounter CRC errors of CMD13, I have tried several > eMMC cards, after mode switch, CMD13 will only gets 0x800 response and > we don't know if card is busy by 0x800 response. Does it change to 0x900 when it is not busy? But anyway the question was: do you have busy detection in your driver? -- 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
