5959b32e36
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@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: Jaehoon Chung <jh80.chung@samsung.com> |
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