MMC: Max blocks value adjustable

The maximum blocks value was hardcoded to 65535 due to a 16 bit
register length.  The value can change for different platforms.
This patch makes the default the current value of 65535, but it
is configurable for other platforms.

Signed-off-by: Matt Waddel <matt.waddel@linaro.org>
Signed-off-by: Andy Fleming <afleming@freescale.com>

drivers/mmc/mmc.c

@@ -33,6 +33,11 @@
 #include <mmc.h>
 #include <div64.h>
 
+/* Set block count limit because of 16 bit register limit on some hardware*/
+#ifndef CONFIG_SYS_MMC_MAX_BLK_COUNT
+#define CONFIG_SYS_MMC_MAX_BLK_COUNT 65535
+#endif
+
 static struct list_head mmc_devices;
 static int cur_dev_num = -1;
 
@@ -139,11 +144,8 @@ mmc_bwrite(int dev_num, ulong start, lbaint_t blkcnt, const void*src)
 		return 0;
 
 	do {
-		/*
-		 * The 65535 constraint comes from some hardware has
-		 * only 16 bit width block number counter
-		 */
-		cur = (blocks_todo > 65535) ? 65535 : blocks_todo;
+		cur = (blocks_todo > CONFIG_SYS_MMC_MAX_BLK_COUNT) ?
+		       CONFIG_SYS_MMC_MAX_BLK_COUNT : blocks_todo;
 		if(mmc_write_blocks(mmc, start, cur, src) != cur)
 			return 0;
 		blocks_todo -= cur;
@@ -215,11 +217,8 @@ static ulong mmc_bread(int dev_num, ulong start, lbaint_t blkcnt, void *dst)
 		return 0;
 
 	do {
-		/*
-		 * The 65535 constraint comes from some hardware has
-		 * only 16 bit width block number counter
-		 */
-		cur = (blocks_todo > 65535) ? 65535 : blocks_todo;
+		cur = (blocks_todo > CONFIG_SYS_MMC_MAX_BLK_COUNT) ?
+		       CONFIG_SYS_MMC_MAX_BLK_COUNT : blocks_todo;
 		if(mmc_read_blocks(mmc, dst, start, cur) != cur)
 			return 0;
 		blocks_todo -= cur;