[MMC] Improve MMC card block size selection
Select a block size for IO based on the read and write block size
combinations, and whether the card supports partial block reads
and/or partial block writes.
If we are able to satisfy block reads but not block writes, mark
the device read only.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/drivers/mmc/mmc_block.c b/drivers/mmc/mmc_block.c
index abcf191..b9837cc 100644
--- a/drivers/mmc/mmc_block.c
+++ b/drivers/mmc/mmc_block.c
@@ -54,6 +54,7 @@
unsigned int usage;
unsigned int block_bits;
+ unsigned int read_only;
};
static DECLARE_MUTEX(open_lock);
@@ -85,12 +86,6 @@
up(&open_lock);
}
-static inline int mmc_blk_readonly(struct mmc_card *card)
-{
- return mmc_card_readonly(card) ||
- !(card->csd.cmdclass & CCC_BLOCK_WRITE);
-}
-
static int mmc_blk_open(struct inode *inode, struct file *filp)
{
struct mmc_blk_data *md;
@@ -102,8 +97,7 @@
check_disk_change(inode->i_bdev);
ret = 0;
- if ((filp->f_mode & FMODE_WRITE) &&
- mmc_blk_readonly(md->queue.card))
+ if ((filp->f_mode & FMODE_WRITE) && md->read_only)
ret = -EROFS;
}
@@ -299,6 +293,12 @@
static unsigned long dev_use[MMC_NUM_MINORS/(8*sizeof(unsigned long))];
+static inline int mmc_blk_readonly(struct mmc_card *card)
+{
+ return mmc_card_readonly(card) ||
+ !(card->csd.cmdclass & CCC_BLOCK_WRITE);
+}
+
static struct mmc_blk_data *mmc_blk_alloc(struct mmc_card *card)
{
struct mmc_blk_data *md;
@@ -310,64 +310,121 @@
__set_bit(devidx, dev_use);
md = kmalloc(sizeof(struct mmc_blk_data), GFP_KERNEL);
- if (md) {
- memset(md, 0, sizeof(struct mmc_blk_data));
-
- md->disk = alloc_disk(1 << MMC_SHIFT);
- if (md->disk == NULL) {
- kfree(md);
- md = ERR_PTR(-ENOMEM);
- goto out;
- }
-
- spin_lock_init(&md->lock);
- md->usage = 1;
-
- ret = mmc_init_queue(&md->queue, card, &md->lock);
- if (ret) {
- put_disk(md->disk);
- kfree(md);
- md = ERR_PTR(ret);
- goto out;
- }
- md->queue.prep_fn = mmc_blk_prep_rq;
- md->queue.issue_fn = mmc_blk_issue_rq;
- md->queue.data = md;
-
- md->disk->major = major;
- md->disk->first_minor = devidx << MMC_SHIFT;
- md->disk->fops = &mmc_bdops;
- md->disk->private_data = md;
- md->disk->queue = md->queue.queue;
- md->disk->driverfs_dev = &card->dev;
-
- /*
- * As discussed on lkml, GENHD_FL_REMOVABLE should:
- *
- * - be set for removable media with permanent block devices
- * - be unset for removable block devices with permanent media
- *
- * Since MMC block devices clearly fall under the second
- * case, we do not set GENHD_FL_REMOVABLE. Userspace
- * should use the block device creation/destruction hotplug
- * messages to tell when the card is present.
- */
-
- sprintf(md->disk->disk_name, "mmcblk%d", devidx);
- sprintf(md->disk->devfs_name, "mmc/blk%d", devidx);
-
- md->block_bits = card->csd.read_blkbits;
-
- blk_queue_hardsect_size(md->queue.queue, 1 << md->block_bits);
-
- /*
- * The CSD capacity field is in units of read_blkbits.
- * set_capacity takes units of 512 bytes.
- */
- set_capacity(md->disk, card->csd.capacity << (card->csd.read_blkbits - 9));
+ if (!md) {
+ ret = -ENOMEM;
+ goto out;
}
- out:
+
+ memset(md, 0, sizeof(struct mmc_blk_data));
+
+ /*
+ * Set the read-only status based on the supported commands
+ * and the write protect switch.
+ */
+ 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)
+ */
+ 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",
+ md->disk->disk_name,
+ 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->disk = alloc_disk(1 << MMC_SHIFT);
+ if (md->disk == NULL) {
+ ret = -ENOMEM;
+ goto err_kfree;
+ }
+
+ spin_lock_init(&md->lock);
+ md->usage = 1;
+
+ ret = mmc_init_queue(&md->queue, card, &md->lock);
+ if (ret)
+ goto err_putdisk;
+
+ md->queue.prep_fn = mmc_blk_prep_rq;
+ md->queue.issue_fn = mmc_blk_issue_rq;
+ md->queue.data = md;
+
+ md->disk->major = major;
+ md->disk->first_minor = devidx << MMC_SHIFT;
+ md->disk->fops = &mmc_bdops;
+ md->disk->private_data = md;
+ md->disk->queue = md->queue.queue;
+ md->disk->driverfs_dev = &card->dev;
+
+ /*
+ * As discussed on lkml, GENHD_FL_REMOVABLE should:
+ *
+ * - be set for removable media with permanent block devices
+ * - be unset for removable block devices with permanent media
+ *
+ * Since MMC block devices clearly fall under the second
+ * case, we do not set GENHD_FL_REMOVABLE. Userspace
+ * should use the block device creation/destruction hotplug
+ * messages to tell when the card is present.
+ */
+
+ sprintf(md->disk->disk_name, "mmcblk%d", devidx);
+ sprintf(md->disk->devfs_name, "mmc/blk%d", devidx);
+
+ blk_queue_hardsect_size(md->queue.queue, 1 << md->block_bits);
+
+ /*
+ * The CSD capacity field is in units of read_blkbits.
+ * set_capacity takes units of 512 bytes.
+ */
+ set_capacity(md->disk, card->csd.capacity << (card->csd.read_blkbits - 9));
return md;
+
+ err_putdisk:
+ put_disk(md->disk);
+ err_kfree:
+ kfree(md);
+ out:
+ return ERR_PTR(ret);
}
static int
@@ -403,12 +460,6 @@
if (!(card->csd.cmdclass & CCC_BLOCK_READ))
return -ENODEV;
- if (card->csd.read_blkbits < 9) {
- printk(KERN_WARNING "%s: read blocksize too small (%u)\n",
- mmc_card_id(card), 1 << card->csd.read_blkbits);
- return -ENODEV;
- }
-
md = mmc_blk_alloc(card);
if (IS_ERR(md))
return PTR_ERR(md);
@@ -419,7 +470,7 @@
printk(KERN_INFO "%s: %s %s %luKiB %s\n",
md->disk->disk_name, mmc_card_id(card), mmc_card_name(card),
- get_capacity(md->disk) >> 1, mmc_blk_readonly(card)?"(ro)":"");
+ get_capacity(md->disk) >> 1, md->read_only ? "(ro)" : "");
mmc_set_drvdata(card, md);
add_disk(md->disk);