3 files changed, 46 insertions, 2 deletions

diff --git a/drivers/mmc/mmc-uclass.c b/drivers/mmc/mmc-uclass.c
index c75892a72c..cb26d841be 100644
--- a/drivers/mmc/mmc-uclass.c
+++ b/drivers/mmc/mmc-uclass.c
@@ -13,6 +13,22 @@
 #include <linux/compat.h>
 #include "mmc_private.h"
 
+int dm_mmc_get_b_max(struct udevice *dev, void *dst, lbaint_t blkcnt)
+{
+	struct dm_mmc_ops *ops = mmc_get_ops(dev);
+	struct mmc *mmc = mmc_get_mmc_dev(dev);
+
+	if (ops->get_b_max)
+		return ops->get_b_max(dev, dst, blkcnt);
+	else
+		return mmc->cfg->b_max;
+}
+
+int mmc_get_b_max(struct mmc *mmc, void *dst, lbaint_t blkcnt)
+{
+	return dm_mmc_get_b_max(mmc->dev, dst, blkcnt);
+}
+
 int dm_mmc_send_cmd(struct udevice *dev, struct mmc_cmd *cmd,
 		    struct mmc_data *data)
 {
diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
index fc3123c3c3..523c055967 100644
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -409,6 +409,16 @@ static int mmc_read_blocks(struct mmc *mmc, void *dst, lbaint_t start,
 	return blkcnt;
 }
 
+#if !CONFIG_IS_ENABLED(DM_MMC)
+static int mmc_get_b_max(struct mmc *mmc, void *dst, lbaint_t blkcnt)
+{
+	if (mmc->cfg->ops->get_b_max)
+		return mmc->cfg->ops->get_b_max(mmc, dst, blkcnt);
+	else
+		return mmc->cfg->b_max;
+}
+#endif
+
 #if CONFIG_IS_ENABLED(BLK)
 ulong mmc_bread(struct udevice *dev, lbaint_t start, lbaint_t blkcnt, void *dst)
 #else
@@ -422,6 +432,7 @@ ulong mmc_bread(struct blk_desc *block_dev, lbaint_t start, lbaint_t blkcnt,
 	int dev_num = block_dev->devnum;
 	int err;
 	lbaint_t cur, blocks_todo = blkcnt;
+	uint b_max;
 
 	if (blkcnt == 0)
 		return 0;
@@ -451,9 +462,10 @@ ulong mmc_bread(struct blk_desc *block_dev, lbaint_t start, lbaint_t blkcnt,
 		return 0;
 	}
 
+	b_max = mmc_get_b_max(mmc, dst, blkcnt);
+
 	do {
-		cur = (blocks_todo > mmc->cfg->b_max) ?
-			mmc->cfg->b_max : blocks_todo;
+		cur = (blocks_todo > b_max) ? b_max : blocks_todo;
 		if (mmc_read_blocks(mmc, dst, start, cur) != cur) {
 			pr_debug("%s: Failed to read blocks\n", __func__);
 			return 0;
diff --git a/include/mmc.h b/include/mmc.h
index e92e920560..5e9d15cb41 100644
--- a/include/mmc.h
+++ b/include/mmc.h
@@ -491,6 +491,19 @@ struct dm_mmc_ops {
 	 * @return 0 if not present, 1 if present, -ve on error
 	 */
 	int (*host_power_cycle)(struct udevice *dev);
+
+	/**
+	 * get_b_max - get maximum length of single transfer
+	 *	       Called before reading blocks from the card,
+	 *	       useful for system which have e.g. DMA limits
+	 *	       on various memory ranges.
+	 *
+	 * @dev:	Device to check
+	 * @dst:	Destination buffer in memory
+	 * @blkcnt:	Total number of blocks in this transfer
+	 * @return maximum number of blocks for this transfer
+	 */
+	int (*get_b_max)(struct udevice *dev, void *dst, lbaint_t blkcnt);
 };
 
 #define mmc_get_ops(dev)        ((struct dm_mmc_ops *)(dev)->driver->ops)
@@ -504,6 +517,7 @@ int dm_mmc_execute_tuning(struct udevice *dev, uint opcode);
 int dm_mmc_wait_dat0(struct udevice *dev, int state, int timeout_us);
 int dm_mmc_host_power_cycle(struct udevice *dev);
 int dm_mmc_deferred_probe(struct udevice *dev);
+int dm_mmc_get_b_max(struct udevice *dev, void *dst, lbaint_t blkcnt);
 
 /* Transition functions for compatibility */
 int mmc_set_ios(struct mmc *mmc);
@@ -514,6 +528,7 @@ int mmc_wait_dat0(struct mmc *mmc, int state, int timeout_us);
 int mmc_set_enhanced_strobe(struct mmc *mmc);
 int mmc_host_power_cycle(struct mmc *mmc);
 int mmc_deferred_probe(struct mmc *mmc);
+int mmc_get_b_max(struct mmc *mmc, void *dst, lbaint_t blkcnt);
 
 #else
 struct mmc_ops {
@@ -524,6 +539,7 @@ struct mmc_ops {
 	int (*getcd)(struct mmc *mmc);
 	int (*getwp)(struct mmc *mmc);
 	int (*host_power_cycle)(struct mmc *mmc);
+	int (*get_b_max)(struct mmc *mmc, void *dst, lbaint_t blkcnt);
 };
 #endif