mtd: nand: read_page() returns max_bitflips

The ecc.read_page() method for nand drivers is changed to return the maximum
number of bitflips that were corrected on any one region covering an ecc step,
This patch doesn't change what the nand code returns to mtd.

This v2 includes the change to the fsl_ifc_nand driver requested by Scott¹.

¹ http://lists.infradead.org/pipermail/linux-mtd/2012-April/040883.html

Signed-off-by: Mike Dunn <mikedunn@newsguy.com>
Acked-by (freescale changes): Scott Wood <scottwood@freescale.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index 671f228..8718eaf 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -1138,6 +1138,7 @@
 	uint8_t *ecc_calc = chip->buffers->ecccalc;
 	uint8_t *ecc_code = chip->buffers->ecccode;
 	uint32_t *eccpos = chip->ecc.layout->eccpos;
+	unsigned int max_bitflips = 0;
 
 	chip->ecc.read_page_raw(mtd, chip, buf, page);
 
@@ -1154,12 +1155,14 @@
 		int stat;
 
 		stat = chip->ecc.correct(mtd, p, &ecc_code[i], &ecc_calc[i]);
-		if (stat < 0)
+		if (stat < 0) {
 			mtd->ecc_stats.failed++;
-		else
+		} else {
 			mtd->ecc_stats.corrected += stat;
+			max_bitflips = max_t(unsigned int, max_bitflips, stat);
+		}
 	}
-	return 0;
+	return max_bitflips;
 }
 
 /**
@@ -1180,6 +1183,7 @@
 	int datafrag_len, eccfrag_len, aligned_len, aligned_pos;
 	int busw = (chip->options & NAND_BUSWIDTH_16) ? 2 : 1;
 	int index = 0;
+	unsigned int max_bitflips = 0;
 
 	/* Column address within the page aligned to ECC size (256bytes) */
 	start_step = data_offs / chip->ecc.size;
@@ -1244,12 +1248,14 @@
 
 		stat = chip->ecc.correct(mtd, p,
 			&chip->buffers->ecccode[i], &chip->buffers->ecccalc[i]);
-		if (stat < 0)
+		if (stat < 0) {
 			mtd->ecc_stats.failed++;
-		else
+		} else {
 			mtd->ecc_stats.corrected += stat;
+			max_bitflips = max_t(unsigned int, max_bitflips, stat);
+		}
 	}
-	return 0;
+	return max_bitflips;
 }
 
 /**
@@ -1271,6 +1277,7 @@
 	uint8_t *ecc_calc = chip->buffers->ecccalc;
 	uint8_t *ecc_code = chip->buffers->ecccode;
 	uint32_t *eccpos = chip->ecc.layout->eccpos;
+	unsigned int max_bitflips = 0;
 
 	for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {
 		chip->ecc.hwctl(mtd, NAND_ECC_READ);
@@ -1289,12 +1296,14 @@
 		int stat;
 
 		stat = chip->ecc.correct(mtd, p, &ecc_code[i], &ecc_calc[i]);
-		if (stat < 0)
+		if (stat < 0) {
 			mtd->ecc_stats.failed++;
-		else
+		} else {
 			mtd->ecc_stats.corrected += stat;
+			max_bitflips = max_t(unsigned int, max_bitflips, stat);
+		}
 	}
-	return 0;
+	return max_bitflips;
 }
 
 /**
@@ -1320,6 +1329,7 @@
 	uint8_t *ecc_code = chip->buffers->ecccode;
 	uint32_t *eccpos = chip->ecc.layout->eccpos;
 	uint8_t *ecc_calc = chip->buffers->ecccalc;
+	unsigned int max_bitflips = 0;
 
 	/* Read the OOB area first */
 	chip->cmdfunc(mtd, NAND_CMD_READOOB, 0, page);
@@ -1337,12 +1347,14 @@
 		chip->ecc.calculate(mtd, p, &ecc_calc[i]);
 
 		stat = chip->ecc.correct(mtd, p, &ecc_code[i], NULL);
-		if (stat < 0)
+		if (stat < 0) {
 			mtd->ecc_stats.failed++;
-		else
+		} else {
 			mtd->ecc_stats.corrected += stat;
+			max_bitflips = max_t(unsigned int, max_bitflips, stat);
+		}
 	}
-	return 0;
+	return max_bitflips;
 }
 
 /**
@@ -1363,6 +1375,7 @@
 	int eccsteps = chip->ecc.steps;
 	uint8_t *p = buf;
 	uint8_t *oob = chip->oob_poi;
+	unsigned int max_bitflips = 0;
 
 	for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {
 		int stat;
@@ -1379,10 +1392,12 @@
 		chip->read_buf(mtd, oob, eccbytes);
 		stat = chip->ecc.correct(mtd, p, oob, NULL);
 
-		if (stat < 0)
+		if (stat < 0) {
 			mtd->ecc_stats.failed++;
-		else
+		} else {
 			mtd->ecc_stats.corrected += stat;
+			max_bitflips = max_t(unsigned int, max_bitflips, stat);
+		}
 
 		oob += eccbytes;
 
@@ -1397,7 +1412,7 @@
 	if (i)
 		chip->read_buf(mtd, oob, i);
 
-	return 0;
+	return max_bitflips;
 }
 
 /**
@@ -1588,7 +1603,7 @@
 	if (oob)
 		ops->oobretlen = ops->ooblen - oobreadlen;
 
-	if (ret)
+	if (ret < 0)
 		return ret;
 
 	if (mtd->ecc_stats.failed - stats.failed)