[MTD] NAND: Combined oob buffer so it's contiguous with data

Ditch the separate oobrbuf and oobwbuf fields from the chip buffers,
and use only a single buffer immediately after the data. This accommodates
NAND controllers such as the OLPC CAFÉ chip, which can't do scatter/gather
DMA so needs the OOB buffer to be contiguous with the data, for both read
and write.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

2 files changed, 6 insertions, 15 deletions

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index 53c66d5c8d1a..29090c6d4819 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -971,7 +971,6 @@ static int nand_do_read_ops(struct mtd_info *mtd, loff_t from,
         page = realpage & chip->pagemask;
 
         col = (int)(from & (mtd->writesize - 1));
-        chip->oob_poi = chip->buffers->oobrbuf;
 
         buf = ops->datbuf;
         oob = ops->oobbuf;
@@ -1270,8 +1269,6 @@ static int nand_do_read_oob(struct mtd_info *mtd, loff_t from,
         realpage = (int)(from >> chip->page_shift);
         page = realpage & chip->pagemask;
 
-        chip->oob_poi = chip->buffers->oobrbuf;
-
         while(1) {
                 sndcmd = chip->ecc.read_oob(mtd, chip, page, sndcmd);
                 buf = nand_transfer_oob(chip, buf, ops);
@@ -1625,7 +1622,9 @@ static int nand_do_write_ops(struct mtd_info *mtd, loff_t to,
             (chip->pagebuf << chip->page_shift) < (to + ops->len))
                 chip->pagebuf = -1;
 
-        chip->oob_poi = chip->buffers->oobwbuf;
+        /* If we're not given explicit OOB data, let it be 0xFF */
+        if (likely(!oob))
+                memset(chip->oob_poi, 0xff, mtd->oobsize);
 
         while(1) {
                 int cached = writelen > bytes && page != blockmask;
@@ -1654,9 +1653,6 @@ static int nand_do_write_ops(struct mtd_info *mtd, loff_t to,
                 }
         }
 
-        if (unlikely(oob))
-                memset(chip->oob_poi, 0xff, mtd->oobsize);
-
         ops->retlen = ops->len - writelen;
         return ret;
 }
@@ -1744,7 +1740,6 @@ static int nand_do_write_oob(struct mtd_info *mtd, loff_t to,
         if (page == chip->pagebuf)
                 chip->pagebuf = -1;
 
-        chip->oob_poi = chip->buffers->oobwbuf;
         memset(chip->oob_poi, 0xff, mtd->oobsize);
         nand_fill_oob(chip, ops->oobbuf, ops);
         status = chip->ecc.write_oob(mtd, chip, page & chip->pagemask);
@@ -2348,8 +2343,8 @@ int nand_scan_tail(struct mtd_info *mtd)
         if (!chip->buffers)
                 return -ENOMEM;
 
-        /* Preset the internal oob write buffer */
-        memset(chip->buffers->oobwbuf, 0xff, mtd->oobsize);
+        /* Set the internal oob buffer location, just after the page data */
+        chip->oob_poi = chip->buffers + mtd->writesize;
 
         /*
          * If no default placement scheme is given, select an appropriate one
diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
index 70420bbae82b..6fc3e07497e0 100644
--- a/include/linux/mtd/nand.h
+++ b/include/linux/mtd/nand.h
@@ -286,9 +286,7 @@ struct nand_ecc_ctrl {
  * struct nand_buffers - buffer structure for read/write
  * @ecccalc:    buffer for calculated ecc
  * @ecccode:    buffer for ecc read from flash
- * @oobwbuf:    buffer for write oob data
  * @databuf:    buffer for data - dynamically sized
- * @oobrbuf:    buffer to read oob data
  *
  * Do not change the order of buffers. databuf and oobrbuf must be in
  * consecutive order.
@@ -296,9 +294,7 @@ struct nand_ecc_ctrl {
 struct nand_buffers {
         uint8_t ecccalc[NAND_MAX_OOBSIZE];
         uint8_t ecccode[NAND_MAX_OOBSIZE];
-        uint8_t oobwbuf[NAND_MAX_OOBSIZE];
-        uint8_t databuf[NAND_MAX_PAGESIZE];
-        uint8_t oobrbuf[NAND_MAX_OOBSIZE];
+        uint8_t databuf[NAND_MAX_PAGESIZE + NAND_MAX_OOBSIZE];
 };
 
 /**