On Wednesday 01 July 2015 03:32 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 s/4K/8k Alexey fat-fingered it seems. ARC cores by default have 8k MMU page size and we saw this issue on ARC SDP boards ! -Vineet > 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
