[PATCH v3 4/5] mtd: rawnand: Introduce a new function nand_check_is_erased_page()

[huobean]

From: Bean Huo <beanhuo@xxxxxxxxxx>

Add a new function nand_check_is_erased_page() in nand_base.c, which is
used to check whether one programmable page is empty or already programmed

Signed-off-by: Bean Huo <beanhuo@xxxxxxxxxx>
---
 drivers/mtd/nand/raw/nand_base.c | 49 ++++++++++++++++++++++++++++++++
 include/linux/mtd/rawnand.h      |  2 ++
 2 files changed, 51 insertions(+)

diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
index b630f7f6a651..2bc9be745bc1 100644
--- a/drivers/mtd/nand/raw/nand_base.c
+++ b/drivers/mtd/nand/raw/nand_base.c
@@ -2584,6 +2584,55 @@ int nand_check_erased_ecc_chunk(void *data, int datalen,
 }
 EXPORT_SYMBOL(nand_check_erased_ecc_chunk);
 
+/**
+ * nand_check_is_erased_page - check if this page is a empty page
+ * @chip: nand chip info structure
+ * @page_data: data buffer containing the data in the page being checked
+ * @oob: indicate if chip->oob_poi points to oob date of the page
+ *
+ * Returns true if this is an un-programmed page, false otherwise.
+ */
+int nand_check_is_erased_page(struct nand_chip *chip, u8 *page_data, bool oob)
+{
+	struct mtd_info *mtd = nand_to_mtd(chip);
+	int ret, i, max_bitflips;
+	u8 *databuf, *eccbuf = NULL;
+	struct mtd_oob_region oobregion;
+	int datasize, eccbytes = 0;
+
+	databuf = page_data;
+	datasize = chip->ecc.size;
+
+	if (oob) {
+		mtd_ooblayout_ecc(mtd, 0, &oobregion);
+		eccbuf = chip->oob_poi + oobregion.offset;
+		eccbytes = chip->ecc.bytes;
+	}
+	max_bitflips = 0;
+
+	for (i = 0; i < chip->ecc.steps; i++) {
+		ret = nand_check_erased_ecc_chunk(databuf, datasize,
+						  eccbuf, eccbytes,
+						  NULL, 0, chip->ecc.strength);
+		if (ret < 0)
+			return false;
+
+		max_bitflips = max(ret, max_bitflips);
+
+		databuf += chip->ecc.size;
+		eccbuf += chip->ecc.bytes;
+	}
+
+	/*
+	 * As for the empty/erased page, bitflips number should be zero or at
+	 * least less than the bitflip_threshold.
+	 */
+	ret =  max_bitflips < mtd->bitflip_threshold;
+
+	return ret;
+}
+EXPORT_SYMBOL(nand_check_is_erased_page);
+
 /**
  * nand_read_page_raw_notsupp - dummy read raw page function
  * @chip: nand chip info structure
diff --git a/include/linux/mtd/rawnand.h b/include/linux/mtd/rawnand.h
index a1bb2acfaf6a..bb97b48859f9 100644
--- a/include/linux/mtd/rawnand.h
+++ b/include/linux/mtd/rawnand.h
@@ -1322,6 +1322,8 @@ int nand_check_erased_ecc_chunk(void *data, int datalen,
 				void *extraoob, int extraooblen,
 				int threshold);
 
+int nand_check_is_erased_page(struct nand_chip *chip, u8 *page_data, bool oob);
+
 int nand_ecc_choose_conf(struct nand_chip *chip,
 			 const struct nand_ecc_caps *caps, int oobavail);
 
-- 
2.17.1