Coremmc multiblock support #351
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fifo_size is defined in bits 5:4 in VR register.
Increase size of alignment fix buffer to 4K to support multiblock transfer.
pussuw
reviewed
Feb 7, 2025
| @@ -416,8 +416,6 @@ config MPFS_EMMCSD | |||
| select ARCH_HAVE_SDIO | |||
| select SDIO_BLOCKSETUP | |||
| select SDIO_DMA | |||
| select FAT_DMAMEMORY | |||
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Does this work with kernel mode? If I remember correctly we had to enable FORCE_INDIRECT and for that we needed FAT_DMAMEMORY, because otherwise the MMC driver and/or MMC DMA would write directly to user space memory. DMA only works with physical addresses (and user addresses are virtual) so this fails miserably.
FORCE_INDIRECT makes the file system read the media in 512B blocks, which are properly aligned AND DMA safe! These 512B blocks are then moved to the user buffer.
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Yes, this does not work in kernel mode as such. So, change not usable.
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Summary
Improve write performance of coremmc sdio driver by enabling multiblock transfer.
Impact
Multiblock transfer requires CONFIG_MMCSD_MULTIBLOCK_LIMIT to be defined according to coremmc
internal buffer size. The unaligned user buffer handling limits the block count to 8 due to 4K aligned buffer.
Because FAT_DMAMEMORY and FAT_FORCE_INDIRECT feature flags are disabled to enable multiblock transfer the emmcsd sdio driver shall also handle unaligned transfer buffer.