[PATCH] S3C24XX large page NAND support

[Ben Dooks]

This adds support for using large page NAND devices
with the S3C24XX NAND controllers. This also adds the 
file Documentation/arm/Samsung-S3C24XX/NAND.txt to
describe the differences.

The basic stratergy is to maintain 3 bytes of ECC for
each 256 byte block read from the NAND which is similar
to the default kernel layout (altough we are using the
hardware ECC generator to make our ECC calculations).

Signed-off-by: Ben Dooks <ben-linux at fluff.org>

Index: linux-2.6.21-tmp/drivers/mtd/nand/s3c2410.c
===================================================================
--- linux-2.6.21-tmp.orig/drivers/mtd/nand/s3c2410.c	2007-04-26 04:08:32.000000000 +0100
+++ linux-2.6.21-tmp/drivers/mtd/nand/s3c2410.c	2007-05-22 12:26:49.000000000 +0100
@@ -473,7 +473,7 @@ static int s3c2440_nand_calculate_ecc(st
 	ecc_code[1] = ecc >> 8;
 	ecc_code[2] = ecc >> 16;
 
-	pr_debug("%s: returning ecc %06lx\n", __func__, ecc);
+	pr_debug("%s: returning ecc %06lx\n", __func__, ecc & 0xffffff);
 
 	return 0;
 }
@@ -630,9 +630,6 @@ static void s3c2410_nand_init_chip(struc
 		chip->ecc.calculate = s3c2410_nand_calculate_ecc;
 		chip->ecc.correct   = s3c2410_nand_correct_data;
 		chip->ecc.mode	    = NAND_ECC_HW;
-		chip->ecc.size	    = 512;
-		chip->ecc.bytes	    = 3;
-		chip->ecc.layout    = &nand_hw_eccoob;
 
 		switch (info->cpu_type) {
 		case TYPE_S3C2410:
@@ -656,6 +653,34 @@ static void s3c2410_nand_init_chip(struc
 	}
 }
 
+/* s3c2410_nand_update_chip
+ *
+ * post-probe chip update, to change any items, such as the
+ * layout for large page nand
+ */
+
+static void s3c2410_nand_update_chip(struct s3c2410_nand_info *info,
+				     struct s3c2410_nand_mtd *nmtd)
+{
+	struct nand_chip *chip = &nmtd->chip;
+
+	printk("%s: chip %p: %d\n", __func__, chip, chip->page_shift);
+
+	if (hardware_ecc) {
+		/* change the behaviour depending on wether we are using
+		 * the large or small page nand device */
+
+		if (chip->page_shift > 10) {
+			chip->ecc.size	    = 256;
+			chip->ecc.bytes	    = 3;
+		} else {
+			chip->ecc.size	    = 512;
+			chip->ecc.bytes	    = 3;
+			chip->ecc.layout    = &nand_hw_eccoob;
+		}
+	}
+}
+
 /* s3c2410_nand_probe
  *
  * called by device layer when it finds a device matching
@@ -762,9 +787,12 @@ static int s3c24xx_nand_probe(struct pla
 
 		s3c2410_nand_init_chip(info, nmtd, sets);
 
-		nmtd->scan_res = nand_scan(&nmtd->mtd, (sets) ? sets->nr_chips : 1);
+		nmtd->scan_res = nand_scan_ident(&nmtd->mtd,
+						 (sets) ? sets->nr_chips : 1);
 
 		if (nmtd->scan_res == 0) {
+			s3c2410_nand_update_chip(info, nmtd);
+			nand_scan_tail(&nmtd->mtd);
 			s3c2410_nand_add_partition(info, nmtd, sets);
 		}
 
Index: linux-2.6.21-tmp/Documentation/arm/Samsung-S3C24XX/NAND.txt
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.21-tmp/Documentation/arm/Samsung-S3C24XX/NAND.txt	2007-05-22 12:23:57.000000000 +0100
@@ -0,0 +1,30 @@
+			S3C24XX NAND Support
+			====================
+
+Introduction
+------------
+
+Small Page NAND
+---------------
+
+The driver uses a 512 byte (1 page) ECC code for this setup. The
+ECC code is not directly compatible with the default kernel ECC
+code, so the driver enforces its own OOB layout and ECC parameters
+
+Large Page NAND
+---------------
+
+The driver is capable of handling NAND flash with a 2KiB page
+size, with support for hardware ECC generation and correction.
+
+Unlike the 512byte page mode, the driver generates ECC data for
+each 256 byte block in an 2KiB page. This means that more than
+one error in a page can be rectified. It also means that the
+OOB layout remains the default kernel layout for these flashes.
+
+
+Document Author
+---------------
+
+Ben Dooks, Copyright 2007 Simtec Electronics
+
Index: linux-2.6.21-tmp/Documentation/arm/Samsung-S3C24XX/Overview.txt
===================================================================
--- linux-2.6.21-tmp.orig/Documentation/arm/Samsung-S3C24XX/Overview.txt	2007-04-26 04:08:32.000000000 +0100
+++ linux-2.6.21-tmp/Documentation/arm/Samsung-S3C24XX/Overview.txt	2007-05-22 12:23:57.000000000 +0100
@@ -156,6 +156,8 @@ NAND
   controller. If there are any problems the latest linux-mtd
   code can be found from http://www.linux-mtd.infradead.org/
 
+  For more information see Documentation/arm/Samsung-S3C24XX/NAND.txt
+
 
 Serial
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