Hi Pierre,
I've been checking my SDIO CMD53 data transfers and I notice the
following:
block size = 256 bytes for my SDIO card.
transfers of 256 bytes uses byte mode ( I expected block mode )
transfers of 512 bytes uses block mode ( because blocks = 2 )
>From the SD spec a single block transfer seems to be valid.
I notice the function mmc_io_rw_extended() in sdio_ops.c seems to select
byte mode when the transfer size is 512 or less when the blocks
parameter variable is 1. In fact blocks is never 0.
Therefore is this a feature or a bug that prevents 256 bytes being sent
in block mode when it is a single complete 1 block of data ?
If it is a bug then I suggest the sdio_io_rw_ext_helper() in sdio_io.c
be able to select byte mode by setting blocks to 0 and then blocks can
be set to 1 to select block mode for a single block.
Have I missed something ?
Technically, there is a bug in sdio_io_rw_ext_helper() in sdio_io.c
211 while (remainder > func->cur_blksize) {
should be, = missing
211 while (remainder >= func->cur_blksize) {
however the resulting call to mmc_io_rw_extended() is the same as blocks
= 1 for both the "block mode" while loop (with the "fix") and the "byte
mode" while loop (without the "fix"). The "byte mode" while loop has a
hard coded value of 1 for the blocks parameter. So the bug is masked. As
I said above, I think the "byte mode" should use a value of 0 for the
blocks parameter.
What do you think ?
Regards,
Dean.
--
Dean Jenkins
Embedded Software Engineer
MontaVista Software (UK)
Professional Services Division
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