[RFC][PATCH][JFFS2] JFFS2 doesn't use OOB at MLC NAND/OneNAND

[Kyungmin Park]

Hi,

It's the preparation patch for the MLC NAND/OneNAND flash.
The current jffs2 implementation at NAND case uses the NOP 2, cleanmarker and data each page 0. It breaks the NOP 1 limitation in MLC flash.

With this patch, we don't write the cleanmarker at oob area.
I'm not sure it should use the cleanmarker at data area as NOR does.
Apart from the cleanmarker, there's serious POR issue, paired page at MLC.

The paired page problem is that if the some page is broken, the paired page is also broken even though it is written correctly at previous time.
That's the reason the cleanmarker is not big issue at this time.

Now we support the NOP 1 and later we have to address this paired page issue. I'm not sure when this problem is addressed.

Any comments are welcome.

Thank you,
Kyungmin Park

Signed-off-by: Kyungmin Park <kyungmin.park at samsung.com>
---
diff --git a/fs/jffs2/erase.c b/fs/jffs2/erase.c
index a1db918..65d7dd7 100644
--- a/fs/jffs2/erase.c
+++ b/fs/jffs2/erase.c
@@ -415,6 +415,7 @@ static void jffs2_mark_erased_block(struct jffs2_sb_info *c, struct jffs2_eraseb
 	/* Cleanmarker in oob area or no cleanmarker at all ? */
 	if (jffs2_cleanmarker_oob(c) || c->cleanmarker_size == 0) {
 
+		/* We only write cleanmarker in case of SLC NAND */
 		if (jffs2_cleanmarker_oob(c)) {
 			if (jffs2_write_nand_cleanmarker(c, jeb))
 				goto filebad;
diff --git a/fs/jffs2/fs.c b/fs/jffs2/fs.c
index ee192af..cbeb822 100644
--- a/fs/jffs2/fs.c
+++ b/fs/jffs2/fs.c
@@ -656,7 +656,9 @@ void jffs2_gc_release_page(struct jffs2_sb_info *c,
 static int jffs2_flash_setup(struct jffs2_sb_info *c) {
 	int ret = 0;
 
-	if (jffs2_cleanmarker_oob(c)) {
+	if (c->mtd->type == MTD_NANDFLASH) {
+		if (!(c->mtd->flags & MTD_OOB_WRITEABLE))
+			printk(KERN_INFO "JFFS2 doesn't use OOB.\n");
 		/* NAND flash... do setup accordingly */
 		ret = jffs2_nand_flash_setup(c);
 		if (ret)
@@ -689,7 +691,7 @@ static int jffs2_flash_setup(struct jffs2_sb_info *c) {
 
 void jffs2_flash_cleanup(struct jffs2_sb_info *c) {
 
-	if (jffs2_cleanmarker_oob(c)) {
+	if (c->mtd->type == MTD_NANDFLASH) {
 		jffs2_nand_flash_cleanup(c);
 	}
 
diff --git a/fs/jffs2/os-linux.h b/fs/jffs2/os-linux.h
index bf64686..27dd4e8 100644
--- a/fs/jffs2/os-linux.h
+++ b/fs/jffs2/os-linux.h
@@ -110,7 +110,7 @@ static inline void jffs2_init_inode_info(struct jffs2_inode_info *f)
 #define jffs2_can_mark_obsolete(c) (c->mtd->flags & (MTD_BIT_WRITEABLE))
 #endif
 
-#define jffs2_cleanmarker_oob(c) (c->mtd->type == MTD_NANDFLASH)
+#define jffs2_cleanmarker_oob(c) (c->mtd->type == MTD_NANDFLASH && (c->mtd->flags & MTD_OOB_WRITEABLE))
 
 #define jffs2_flash_write_oob(c, ofs, len, retlen, buf) ((c)->mtd->write_oob((c)->mtd, ofs, len, retlen, buf))
 #define jffs2_flash_read_oob(c, ofs, len, retlen, buf) ((c)->mtd->read_oob((c)->mtd, ofs, len, retlen, buf))
diff --git a/fs/jffs2/scan.c b/fs/jffs2/scan.c
diff --git a/fs/jffs2/wbuf.c b/fs/jffs2/wbuf.c
diff --git a/include/mtd/mtd-abi.h b/include/mtd/mtd-abi.h
index f71dac4..89eb3eb 100644
--- a/include/mtd/mtd-abi.h
+++ b/include/mtd/mtd-abi.h
@@ -30,12 +30,14 @@ struct mtd_oob_buf {
 #define MTD_BIT_WRITEABLE	0x800	/* Single bits can be flipped */
 #define MTD_NO_ERASE		0x1000	/* No erase necessary */
 #define MTD_STUPID_LOCK		0x2000	/* Always locked after reset */
+#define MTD_OOB_WRITEABLE	0x4000	/* Use Out-Of-Band area */
 
 // Some common devices / combinations of capabilities
 #define MTD_CAP_ROM		0
 #define MTD_CAP_RAM		(MTD_WRITEABLE | MTD_BIT_WRITEABLE | MTD_NO_ERASE)
 #define MTD_CAP_NORFLASH	(MTD_WRITEABLE | MTD_BIT_WRITEABLE)
-#define MTD_CAP_NANDFLASH	(MTD_WRITEABLE)
+#define MTD_CAP_NANDFLASH	(MTD_WRITEABLE | MTD_OOB_WRITEABLE)
+#define MTD_CAP_MLC_NANDFLASH	(MTD_WRITEABLE)
 
 /* ECC byte placement */
 #define MTD_NANDECC_OFF		0	// Switch off ECC (Not recommended)