On 20/10/17 15:30, Adrian Hunter wrote: > On 19/10/17 14:44, Adrian Hunter wrote: >> On 18/10/17 09:16, Adrian Hunter wrote: >>> On 11/10/17 16:58, Ulf Hansson wrote: >>>> On 11 October 2017 at 14:58, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote: >>>>> On 11/10/17 15:13, Ulf Hansson wrote: >>>>>> On 10 October 2017 at 15:31, Adrian Hunter <adrian.hunter@xxxxxxxxx> wrote: >>>>>>> On 10/10/17 16:08, Ulf Hansson wrote: >>>>>>>> [...] >>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> I have also run some test on my ux500 board and enabling the blkmq >>>>>>>>>>>> path via the new MMC Kconfig option. My idea was to run some iozone >>>>>>>>>>>> comparisons between the legacy path and the new blkmq path, but I just >>>>>>>>>>>> couldn't get to that point because of the following errors. >>>>>>>>>>>> >>>>>>>>>>>> I am using a Kingston 4GB SDHC card, which is detected and mounted >>>>>>>>>>>> nicely. However, when I decide to do some writes to the card I get the >>>>>>>>>>>> following errors. >>>>>>>>>>>> >>>>>>>>>>>> root@ME:/mnt/sdcard dd if=/dev/zero of=testfile bs=8192 count=5000 conv=fsync >>>>>>>>>>>> [ 463.714294] mmci-pl18x 80126000.sdi0_per1: error during DMA transfer! >>>>>>>>>>>> [ 464.722656] mmci-pl18x 80126000.sdi0_per1: error during DMA transfer! >>>>>>>>>>>> [ 466.081481] mmci-pl18x 80126000.sdi0_per1: error during DMA transfer! >>>>>>>>>>>> [ 467.111236] mmci-pl18x 80126000.sdi0_per1: error during DMA transfer! >>>>>>>>>>>> [ 468.669647] mmci-pl18x 80126000.sdi0_per1: error during DMA transfer! >>>>>>>>>>>> [ 469.685699] mmci-pl18x 80126000.sdi0_per1: error during DMA transfer! >>>>>>>>>>>> [ 471.043334] mmci-pl18x 80126000.sdi0_per1: error during DMA transfer! >>>>>>>>>>>> [ 472.052337] mmci-pl18x 80126000.sdi0_per1: error during DMA transfer! >>>>>>>>>>>> [ 473.342651] mmci-pl18x 80126000.sdi0_per1: error during DMA transfer! >>>>>>>>>>>> [ 474.323760] mmci-pl18x 80126000.sdi0_per1: error during DMA transfer! >>>>>>>>>>>> [ 475.544769] mmci-pl18x 80126000.sdi0_per1: error during DMA transfer! >>>>>>>>>>>> [ 476.539031] mmci-pl18x 80126000.sdi0_per1: error during DMA transfer! >>>>>>>>>>>> [ 477.748474] mmci-pl18x 80126000.sdi0_per1: error during DMA transfer! >>>>>>>>>>>> [ 478.724182] mmci-pl18x 80126000.sdi0_per1: error during DMA transfer! >>>>>>>>>>>> >>>>>>>>>>>> I haven't yet got the point of investigating this any further, and >>>>>>>>>>>> unfortunate I have a busy schedule with traveling next week. I will do >>>>>>>>>>>> my best to look into this as soon as I can. >>>>>>>>>>>> >>>>>>>>>>>> Perhaps you have some ideas? >>>>>>>>>>> >>>>>>>>>>> The behaviour depends on whether you have MMC_CAP_WAIT_WHILE_BUSY. Try >>>>>>>>>>> changing that and see if it makes a difference. >>>>>>>>>> >>>>>>>>>> Yes, it does! I disabled MMC_CAP_WAIT_WHILE_BUSY (and its >>>>>>>>>> corresponding code in mmci.c) and the errors goes away. >>>>>>>>>> >>>>>>>>>> When I use MMC_CAP_WAIT_WHILE_BUSY I get these problems: >>>>>>>>>> >>>>>>>>>> [ 223.820983] mmci-pl18x 80126000.sdi0_per1: error during DMA transfer! >>>>>>>>>> [ 224.815795] mmci-pl18x 80126000.sdi0_per1: error during DMA transfer! >>>>>>>>>> [ 226.034881] mmci-pl18x 80126000.sdi0_per1: error during DMA transfer! >>>>>>>>>> [ 227.112884] mmci-pl18x 80126000.sdi0_per1: error during DMA transfer! >>>>>>>>>> [ 227.220275] mmc0: Card stuck in wrong state! mmcblk0 mmc_blk_card_stuck >>>>>>>>>> [ 228.686798] mmci-pl18x 80126000.sdi0_per1: error during DMA transfer! >>>>>>>>>> [ 229.892150] mmci-pl18x 80126000.sdi0_per1: error during DMA transfer! >>>>>>>>>> [ 231.031890] mmci-pl18x 80126000.sdi0_per1: error during DMA transfer! >>>>>>>>>> [ 232.239013] mmci-pl18x 80126000.sdi0_per1: error during DMA transfer! >>>>>>>>>> 5000+0 records in >>>>>>>>>> 5000+0 records out >>>>>>>>>> root@ME:/mnt/sdcard >>>>>>>>>> >>>>>>>>>> I looked at the new blkmq code from patch v10 13/15. It seems like the >>>>>>>>>> MMC_CAP_WAIT_WHILE_BUSY is used to determine whether the async request >>>>>>>>>> mechanism should be used or not. Perhaps I didn't looked close enough, >>>>>>>>>> but maybe you could elaborate on why this seems to be the case!? >>>>>>>>> >>>>>>>>> MMC_CAP_WAIT_WHILE_BUSY is necessary because it means that a data transfer >>>>>>>>> request has finished when the host controller calls mmc_request_done(). i.e. >>>>>>>>> polling the card is not necessary. >>>>>>>> >>>>>>>> Well, that is a rather big change on its own. Earlier we polled with >>>>>>>> CMD13 to verify that the card has moved back to the transfer state, in >>>>>>>> case it was a write. And that was no matter of MMC_CAP_WAIT_WHILE_BUSY >>>>>>>> was set or not. Right!? >>>>>>> >>>>>>> Yes >>>>>>> >>>>>>>> >>>>>>>> I am not sure it's a good idea to bypass that validation, it seems >>>>>>>> fragile to rely only on the busy detection on DAT line for writes. >>>>>>> >>>>>>> Can you cite something from the specifications that backs that up, because I >>>>>>> couldn't find anything to suggest that CMD13 polling was expected. >>>>>> >>>>>> No I can't, but I don't see why that matters. >>>>>> >>>>>> My point is, if we want to go down that road by avoiding the CMD13 >>>>>> polling, that needs to be a separate change, which we can test and >>>>>> confirm on its own. >>>>>> >>>>>>> >>>>>>>> >>>>>>>>> >>>>>>>>> Have you tried V9 or V10. There was a fix in V9 related to calling >>>>>>>>> ->post_req() which could mess up DMA. >>>>>>>> >>>>>>>> I have used V10. >>>>>>>> >>>>>>>>> >>>>>>>>> The other thing that could go wrong with DMA is if it cannot accept >>>>>>>>> ->post_req() being called from mmc_request_done(). >>>>>>>> >>>>>>>> I don't think mmci has a problem with that, however why do you want to >>>>>>>> do this? Wouldn't that defeat some of the benefits with the async >>>>>>>> request mechanism? >>>>>>> >>>>>>> Perhaps - but it would need to be tested. If there are more requests >>>>>>> waiting, one optimization could be to defer ->post_req() until after the >>>>>>> next request is started. >>>>>> >>>>>> This is already proven, because this how the existing mmc async >>>>>> request mechanism works. >>>>>> >>>>>> In ->post_req() callbacks, host drivers may do dma_unmap_sg(), which >>>>>> is something that could be costly and therefore it's better to start a >>>>>> new request before, such these things can go on in parallel. >>>>> >>>>> OK I will make a patch that takes care of both issues. That will also mean >>>>> the request is not completed in the ->done() callback because ->post_req() >>>>> must precede block layer completion. >>>> >>>> Right. >>>> >>>> Actually completing the request in the ->done callback, may still be >>>> possible, because in principle it only needs to inform the other >>>> prepared request that it may start, before it continues to post >>>> process/completes the current one. >>>> >>>> However, by looking at for example how mmci.c works, it actually holds >>>> its spinlock while it calls mmc_request_done(). The same spinlock is >>>> taken in the ->request() function, but not in the ->post_req() >>>> function. In other words, completing the request in the ->done() >>>> callback, would make mmci to keep the spinlock held throughout the >>>> post processing cycle, which then prevents the next request from being >>>> started. >>>> >>>> So my conclusion is, let's start a as you suggested, by not completing >>>> the request in ->done() as to maintain existing behavior. Then we can >>>> address optimizations on top, which very likely will involve doing >>>> changes to host drivers as well. >>> >>> Have you tested the latest version now? >>> >> >> Ping? > > Still ping? How is your silence in any way an acceptable way to execute your responsibilities as maintainer! -- 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
