1. 17 8月, 2015 1 次提交
    • A
      mmc: dw_mmc: handle data blocks > than 4kB if IDMAC is used · 5959b32e
      Alexey Brodkin 提交于
      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: NAlexey Brodkin <abrodkin@synopsys.com>
      Cc: Seungwon Jeon <tgih.jun@samsung.com>
      Cc: Jaehoon Chung <jh80.chung@samsung.com>
      Cc: Ulf Hansson <ulf.hansson@linaro.org>
      Cc: arc-linux-dev@synopsys.com
      Cc: linux-kernel@vger.kernel.org
      Signed-off-by: NJaehoon Chung <jh80.chung@samsung.com>
      5959b32e
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