[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.c b/drivers/mmc/mmc.c
index eb41391e06e938a5a0607b90defab00f82fd9827..6696f71363b92bc3c2744b3bd3ffe243ec2f1714 100644 (file)
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -550,6 +550,11 @@ static void mmc_decode_csd(struct mmc_card *card)
                csd->capacity     = (1 + m) << (e + 2);
 
                csd->read_blkbits = UNSTUFF_BITS(resp, 80, 4);
+               csd->read_partial = UNSTUFF_BITS(resp, 79, 1);
+               csd->write_misalign = UNSTUFF_BITS(resp, 78, 1);
+               csd->read_misalign = UNSTUFF_BITS(resp, 77, 1);
+               csd->write_blkbits = UNSTUFF_BITS(resp, 22, 4);
+               csd->write_partial = UNSTUFF_BITS(resp, 21, 1);
        } else {
                /*
                 * We only understand CSD structure v1.1 and v1.2.
@@ -579,6 +584,11 @@ static void mmc_decode_csd(struct mmc_card *card)
                csd->capacity     = (1 + m) << (e + 2);
 
                csd->read_blkbits = UNSTUFF_BITS(resp, 80, 4);
+               csd->read_partial = UNSTUFF_BITS(resp, 79, 1);
+               csd->write_misalign = UNSTUFF_BITS(resp, 78, 1);
+               csd->read_misalign = UNSTUFF_BITS(resp, 77, 1);
+               csd->write_blkbits = UNSTUFF_BITS(resp, 22, 4);
+               csd->write_partial = UNSTUFF_BITS(resp, 21, 1);
        }
 }
 

diff --git a/drivers/mmc/mmc_block.c b/drivers/mmc/mmc_block.c
index abcf19116d70af5af3289551fbb5d5317d000be1..b9837cc5b9ac0a871a65350d3b8ed36481a37de5 100644 (file)
--- a/drivers/mmc/mmc_block.c
+++ b/drivers/mmc/mmc_block.c
@@ -54,6 +54,7 @@ struct mmc_blk_data {
 
        unsigned int    usage;
        unsigned int    block_bits;
+       unsigned int    read_only;
 };
 
 static DECLARE_MUTEX(open_lock);
@@ -85,12 +86,6 @@ static void mmc_blk_put(struct mmc_blk_data *md)
        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 @@ static int mmc_blk_open(struct inode *inode, struct file *filp)
                        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 int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
 
 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 @@ static struct mmc_blk_data *mmc_blk_alloc(struct mmc_card *card)
        __set_bit(devidx, dev_use);
 
        md = kmalloc(sizeof(struct mmc_blk_data), GFP_KERNEL);
-       if (md) {
-               memset(md, 0, sizeof(struct mmc_blk_data));
+       if (!md) {
+               ret = -ENOMEM;
+               goto out;
+       }
 
-               md->disk = alloc_disk(1 << MMC_SHIFT);
-               if (md->disk == NULL) {
-                       kfree(md);
-                       md = ERR_PTR(-ENOMEM);
-                       goto out;
-               }
+       memset(md, 0, sizeof(struct mmc_blk_data));
 
-               spin_lock_init(&md->lock);
-               md->usage = 1;
+       /*
+        * Set the read-only status based on the supported commands
+        * and the write protect switch.
+        */
+       md->read_only = mmc_blk_readonly(card);
 
-               ret = mmc_init_queue(&md->queue, card, &md->lock);
-               if (ret) {
-                       put_disk(md->disk);
-                       kfree(md);
-                       md = ERR_PTR(ret);
-                       goto out;
+       /*
+        * 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;
                }
-               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;
+       /*
+        * 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;
+       }
 
-               /*
-                * 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.
-                */
+       md->disk = alloc_disk(1 << MMC_SHIFT);
+       if (md->disk == NULL) {
+               ret = -ENOMEM;
+               goto err_kfree;
+       }
 
-               sprintf(md->disk->disk_name, "mmcblk%d", devidx);
-               sprintf(md->disk->devfs_name, "mmc/blk%d", devidx);
+       spin_lock_init(&md->lock);
+       md->usage = 1;
 
-               md->block_bits = card->csd.read_blkbits;
+       ret = mmc_init_queue(&md->queue, card, &md->lock);
+       if (ret)
+               goto err_putdisk;
 
-               blk_queue_hardsect_size(md->queue.queue, 1 << md->block_bits);
+       md->queue.prep_fn = mmc_blk_prep_rq;
+       md->queue.issue_fn = mmc_blk_issue_rq;
+       md->queue.data = md;
 
-               /*
-                * 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));
-       }
- out:
+       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 @@ static int mmc_blk_probe(struct mmc_card *card)
        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 @@ static int mmc_blk_probe(struct mmc_card *card)
 
        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);

diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
index 18fc77f682de8dcf629c83945c4595fd3cc0b82c..7f7d406842881780fab046d7f129462e4ec7892a 100644 (file)
--- a/include/linux/mmc/card.h
+++ b/include/linux/mmc/card.h
@@ -30,7 +30,12 @@ struct mmc_csd {
        unsigned int            tacc_ns;
        unsigned int            max_dtr;
        unsigned int            read_blkbits;
+       unsigned int            write_blkbits;
        unsigned int            capacity;
+       unsigned int            read_partial:1,
+                               read_misalign:1,
+                               write_partial:1
+                               write_misalign:1;
 };
 
 struct sd_scr {