cmd: mmc: Allow using partition name in mmc erase command

The mmc erase command currently requires blk# and cnt parameters
which can be obtained using the part start and part size commands
if the entire partition needs to be erased.

Simplify the use of the mmc erase command by allowing the partition
name to be specified directly.

Signed-off-by: Tomas Paukrt <tomaspaukrt@email.cz>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
diff --git a/cmd/mmc.c b/cmd/mmc.c
index 9a841c2..c0c23ee 100644
--- a/cmd/mmc.c
+++ b/cmd/mmc.c
@@ -473,17 +473,25 @@
 			int argc, char *const argv[])
 {
 	struct mmc *mmc;
+	struct disk_partition info;
 	u32 blk, cnt, n;
 
-	if (argc != 3)
+	if (argc < 2 || argc > 3)
 		return CMD_RET_USAGE;
 
-	blk = hextoul(argv[1], NULL);
-	cnt = hextoul(argv[2], NULL);
-
 	mmc = init_mmc_device(curr_device, false);
 	if (!mmc)
 		return CMD_RET_FAILURE;
+
+	if (argc == 3) {
+		blk = hextoul(argv[1], NULL);
+		cnt = hextoul(argv[2], NULL);
+	} else if (part_get_info_by_name(mmc_get_blk_desc(mmc), argv[1], &info) >= 0) {
+		blk = info.start;
+		cnt = info.size;
+	} else {
+		return CMD_RET_FAILURE;
+	}
 
 	printf("MMC erase: dev # %d, block # %d, count %d ... ",
 	       curr_device, blk, cnt);
@@ -1290,6 +1298,7 @@
 	"mmc swrite addr blk#\n"
 #endif
 	"mmc erase blk# cnt\n"
+	"mmc erase partname\n"
 	"mmc rescan [mode]\n"
 	"mmc part - lists available partition on current mmc device\n"
 	"mmc dev [dev] [part] [mode] - show or set current mmc device [partition] and set mode\n"
diff --git a/doc/usage/cmd/mmc.rst b/doc/usage/cmd/mmc.rst
index 5a64400..55391fd 100644
--- a/doc/usage/cmd/mmc.rst
+++ b/doc/usage/cmd/mmc.rst
@@ -15,6 +15,7 @@
     mmc read addr blk# cnt
     mmc write addr blk# cnt
     mmc erase blk# cnt
+    mmc erase partname
     mmc rescan [mode]
     mmc part
     mmc dev [dev] [part] [mode]
@@ -44,12 +45,15 @@
     cnt
         block count
 
-The 'mmc erase' command erases *cnt* blocks on the MMC device starting at block *blk#*.
+The 'mmc erase' command erases *cnt* blocks on the MMC device starting at block *blk#* or
+the entire partition specified by *partname*.
 
     blk#
         start block offset
     cnt
         block count
+    partname
+        partition name
 
 The 'mmc rescan' command scans the available MMC device.