Hi, Alexey. Sorry for reviewing late. i missed this patch. I will check your patch and reply at mailing. Thanks a lot for noticing this. Best Regards, Jaehoon Chung On 07/01/2015 07:02 PM, Alexey Brodkin wrote: > Hi Jaehoon, Seungwon, Ulf, > > On Thu, 2015-06-25 at 11:25 +0300, Alexey Brodkin wrote: >> As per DW MobileStorage databook "each descriptor can transfer up to >> 4kB >> of data in chained mode", moreover buffer size that is put in "des1" >> is >> limited to 13 bits, i.e. for example on attempt to >> IDMAC_SET_BUFFER1_SIZE(desc, 8192) size value that's effectively >> written >> will be 0. >> >> On the platform with 8kB PAGE_SIZE I see dw_mmc gets data blocks in >> SG-list of 8kB size and that leads to unpredictable behavior of the >> SD/MMC controller. >> >> In particular on write to FAT partition of SD-card the controller >> will >> stuck in the middle of DMA transaction. >> >> Solution to the problem is simple - we need to pass large (> 4kB) >> data >> buffers to the controller via multiple descriptors. And that's what >> that change does. >> >> What's interesting I did try original driver on same platform but >> configured with 4kB PAGE_SIZE and may confirm that data blocks passed >> in SG-list to dw_mmc never exeed 4kB limit - that explains why nobody >> ever faced a problem I did. >> >> Signed-off-by: Alexey Brodkin <abrodkin@xxxxxxxxxxxx> >> Cc: Seungwon Jeon <tgih.jun@xxxxxxxxxxx> >> Cc: Jaehoon Chung <jh80.chung@xxxxxxxxxxx> >> Cc: Ulf Hansson <ulf.hansson@xxxxxxxxxx> >> Cc: arc-linux-dev@xxxxxxxxxxxx >> Cc: linux-kernel@xxxxxxxxxxxxxxx >> --- >> drivers/mmc/host/dw_mmc.c | 109 ++++++++++++++++++++++++++++++------ >> ---------- > > I'm wondering if there're any comments on that patch or if it could be > applied? > > It fixes a real problem on systems on 4K PAGE_SIZE so would be good to > have it in upstream. In particular this is the case with ARC AXS board > which made its way in upstream kernel recently. > > Regards, > Alexey-- > 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 > -- 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
