[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>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 4 insertions, 45 deletions

diff --git a/drivers/mmc/mmc_block.c b/drivers/mmc/mmc_block.c
index d6fcc467b503..a0e0dad1b419 100644
--- a/drivers/mmc/mmc_block.c
+++ b/drivers/mmc/mmc_block.c
@@ -319,52 +319,11 @@ static struct mmc_blk_data *mmc_blk_alloc(struct mmc_card *card)
         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) {