Am 07.10.2014 um 17:25 schrieb Jens Axboe: > On 10/07/2014 03:37 AM, Oleksij Rempel wrote: >> Am 04.10.2014 um 19:00 schrieb Jens Axboe: >>> On 2014-10-04 00:59, Oleksij Rempel wrote: >>>> Hello Jens, >>>> >>>> i hope it is OK to ask you directly, i didn't found better way to do >>>> this. >>>> I'm writing MMC driver based on reverse engineering for au6601 mmc >>>> controller. This driver uses MMC API, and last one trying to use BLK API >>>> as directly as possible. So far so gut, but i have a problem by using SG >>>> requests with DMA without conversation. This controller accepts only >>>> addresses with this mask 0xffff.f000 - also page aligned. >>>> Till now i tried different QUEUE_FLAG_ flags and blk_queue settings, but >>>> i never had absolute aligned quarantine. >>>> Please tell me if i do some thing wrong or go in the wrong direction. >>> >>> Unless you can accept a 4kb hardware block size (and I'm assuming you >>> cannot, since you need to support 512b file systems?), then you'd have >>> to bounce the requests that don't align properly. You can fix some of >>> them by setting blk_queue_dma_alignment(q, 4095). >> >> I needed to include MMC list with Ulf Hansson at the beginning, so here >> we are. >> >> Hi Ulf, >> >> here is the list of drivers which do care about dma alignment . Some of >> them use bounce_buffer, some will use PIO instead of DMA, for not >> aligned requests: >> >> dw_mmc.c: dw_mci_pre_dma_transfer >> wbsd.c >> usdhi6rol0.c >> tmio_mmc_dma.c >> sunxi-mmc.c >> sdhci.c >> pxamci.c >> mvsdio.c >> au6601.c(not upstream jet) >> >> The problem of all this driver is that each of them use own solution. I >> think this code can be moved to some common place. For example, it can >> be done in drivers/mmc/card/queue.c and enabled by >> mmc_host_dma_alignment variable. Or provide a mmc_sg_align() function, >> which should be called explicatively by driver. >> >> Which option is preferable? > > I would roll a block version that they all can use, you can look at > block/bounce.c for inspiration. That file deals with bouncing higher > pages to lower memory, so it's not exactly what you want. But the metod > of allocating a new bio that meets criteria and copying data over, that > is the same that you need. Ok, i will need to setup testing board for this kind of work. It will take some time. -- Regards, Oleksij
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