[U-Boot] [PATCH] [nand] Implement nand_extent_skip_bad

[Pantelis Antoniou]

When accessing nand any bad blocks encountered are skipped, with no
indication about the amount of bad blocks encountered.
While this is normally fine, when you have to write a large amount
of data in chunks, you need to account for the skipped amount due
to the presence of the bad blocks.

nand_extend_skip_bad() returns the offset where the next access
should occur.

Signed-off-by: Pantelis Antoniou <panto at antoniou-consulting.com>
---
 drivers/mtd/nand/nand_util.c | 50 ++++++++++++++++++++++++++++++++++++++++++++
 include/nand.h               |  2 ++
 2 files changed, 52 insertions(+)

diff --git a/drivers/mtd/nand/nand_util.c b/drivers/mtd/nand/nand_util.c
index 2ba0c5e..a25a4cb 100644
--- a/drivers/mtd/nand/nand_util.c
+++ b/drivers/mtd/nand/nand_util.c
@@ -684,6 +684,56 @@ int nand_read_skip_bad(nand_info_t *nand, loff_t offset, size_t *length,
 	return 0;
 }
 
+/**
+ * nand_extent_skip_bad:
+ *
+ * Find the extent of a chunk, return the offset where it ends
+ * Blocks that are marked bad are skipped and the next block is examined
+ * instead as long as the extend is short enough to fit even after skipping the
+ * bad blocks.
+ *
+ * @param nand NAND device
+ * @param offset offset in flash
+ * @param length extend length
+ * @return next offset in case of success (loff_t)-1 on error
+ */
+loff_t nand_extent_skip_bad(nand_info_t *nand, loff_t offset, size_t length)
+{
+	size_t block_len, block_off;
+	loff_t block_start;
+
+	if ((offset & (nand->writesize - 1)) != 0) {
+		printf ("%s: Attempt to check extend non page aligned data\n",
+				__func__);
+		return (loff_t)-1;
+	}
+
+	while (length > 0) {
+
+		if (offset >= nand->size) {
+			printf("%s: offset >= nand->size (%llx >= %llx)\n",
+					__func__, offset, nand->size);
+			return (loff_t)-1;
+		}
+
+		block_start = offset & ~(loff_t)(nand->erasesize - 1);
+		block_off = offset & (nand->erasesize - 1);
+		block_len = nand->erasesize - block_off;
+		if (block_len > length)		/* left over */
+			block_len = length;
+
+		if (!nand_block_isbad(nand, block_start))
+			length -= block_len;
+		else
+			debug("%s: bad block at %llx (left %x)\n",
+					__func__, block_start, length);
+
+		offset += block_len;
+	}
+
+	return offset;
+}
+
 #ifdef CONFIG_CMD_NAND_TORTURE
 
 /**
diff --git a/include/nand.h b/include/nand.h
index dded4e2..710c11a 100644
--- a/include/nand.h
+++ b/include/nand.h
@@ -168,3 +168,5 @@ __attribute__((noreturn)) void nand_boot(void);
 #define ENV_OFFSET_SIZE 8
 int get_nand_env_oob(nand_info_t *nand, unsigned long *result);
 #endif
+
+loff_t nand_extent_skip_bad(nand_info_t *nand, loff_t offset, size_t length);
-- 
1.7.12