Re: 2GB MMC/SD cards

Daniel Drake
2006-08-13T10:04:41Z

Hi Pierre,

Pierre Ossman wrote:
> Suggested patch included.

What's the status on this patch? A Gentoo user at
http://bugs.gentoo.org/142172 reports that it is required for him to be
able to access his card, so it definitely works in some form.

>
> [MMC] Always use a sector size of 512 bytes
>
> Both MMC and SD specifications specify (although a bit unclearly in the MMC
> case) that a sector size of 512 bytes must always be supported by the card.
>
> Cards can report larger "native" size than this, and cards >= 2 GB even
> must do so. Most other readers use 512 bytes even for these cards. We should
> do the same to be compatible.
>
> Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>
> ---
>
> drivers/mmc/mmc_block.c | 49 ++++-------------------------------------------
> 1 files changed, 4 insertions(+), 45 deletions(-)
>
> diff --git a/drivers/mmc/mmc_block.c b/drivers/mmc/mmc_block.c
> index 587458b..96049e2 100644
> --- a/drivers/mmc/mmc_block.c
> +++ b/drivers/mmc/mmc_block.c
> @@ -325,52 +325,11 @@ static struct mmc_blk_data *mmc_blk_allo
> md->read_only = mmc_blk_readonly(card);
>
> /*
> - * Figure out a workable block size. MMC cards have:
> - * - two block sizes, one for read and one for write.
> - * - may support partial reads and/or writes
> - * (allows block sizes smaller than specified)
> + * Both SD and MMC specifications state (although a bit
> + * unclearly in the MMC case) that a block size of 512
> + * bytes must always be supported by the card.
> */
> - md->block_bits = card->csd.read_blkbits;
> - if (card->csd.write_blkbits != card->csd.read_blkbits) {
> - if (card->csd.write_blkbits < card->csd.read_blkbits &&
> - card->csd.read_partial) {
> - /*
> - * write block size is smaller than read block
> - * size, but we support partial reads, so choose
> - * the smaller write block size.
> - */
> - md->block_bits = card->csd.write_blkbits;
> - } else if (card->csd.write_blkbits > card->csd.read_blkbits &&
> - card->csd.write_partial) {
> - /*
> - * read block size is smaller than write block
> - * size, but we support partial writes. Use read
> - * block size.
> - */
> - } else {
> - /*
> - * We don't support this configuration for writes.
> - */
> - printk(KERN_ERR "%s: unable to select block size for "
> - "writing (rb%u wb%u rp%u wp%u)\n",
> - mmc_card_id(card),
> - 1 << card->csd.read_blkbits,
> - 1 << card->csd.write_blkbits,
> - card->csd.read_partial,
> - card->csd.write_partial);
> - md->read_only = 1;
> - }
> - }
> -
> - /*
> - * Refuse to allow block sizes smaller than 512 bytes.
> - */
> - if (md->block_bits < 9) {
> - printk(KERN_ERR "%s: unable to support block size %u\n",
> - mmc_card_id(card), 1 << md->block_bits);
> - ret = -EINVAL;
> - goto err_kfree;
> - }
> + md->block_bits = 9;
>
> md->disk = alloc_disk(1 << MMC_SHIFT);
> if (md->disk == NULL) {