Re: 2GB MMC/SD cards

Pierre Ossman
2006-06-08T23:01:47Z

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Suggested patch included.

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[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) {