[MTD] [OneNAND] Add write-while-program support

OneNAND write-while-program method of writing improves performance,
compared with ordinary writes, by transferring data to OneNAND's
RAM buffers atthe same time as programming the NAND core.

When writing several NAND pages at a time, an improvement of
12% to 25% is seen.
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Adrian Hunter <adrian.hunter@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/onenand/onenand_base.c

@@ -1455,7 +1455,8 @@ static int onenand_write_ops_nolock(struct mtd_info *mtd, loff_t to,
 				struct mtd_oob_ops *ops)
 {
 	struct onenand_chip *this = mtd->priv;
-	int written = 0, column, thislen, subpage;
+	int written = 0, column, thislen = 0, subpage = 0;
+	int prev = 0, prevlen = 0, prev_subpage = 0, first = 1;
 	int oobwritten = 0, oobcolumn, thisooblen, oobsize;
 	size_t len = ops->len;
 	size_t ooblen = ops->ooblen;
@@ -1482,6 +1483,10 @@ static int onenand_write_ops_nolock(struct mtd_info *mtd, loff_t to,
                 return -EINVAL;
         }
 
+	/* Check zero length */
+	if (!len)
+		return 0;
+
 	if (ops->mode == MTD_OOB_AUTO)
 		oobsize = this->ecclayout->oobavail;
 	else
@@ -1492,79 +1497,121 @@ static int onenand_write_ops_nolock(struct mtd_info *mtd, loff_t to,
 	column = to & (mtd->writesize - 1);
 
 	/* Loop until all data write */
-	while (written < len) {
-		u_char *wbuf = (u_char *) buf;
+	while (1) {
+		if (written < len) {
+			u_char *wbuf = (u_char *) buf;
 
-		thislen = min_t(int, mtd->writesize - column, len - written);
-		thisooblen = min_t(int, oobsize - oobcolumn, ooblen - oobwritten);
+			thislen = min_t(int, mtd->writesize - column, len - written);
+			thisooblen = min_t(int, oobsize - oobcolumn, ooblen - oobwritten);
 
-		cond_resched();
+			cond_resched();
 
-		this->command(mtd, ONENAND_CMD_BUFFERRAM, to, thislen);
+			this->command(mtd, ONENAND_CMD_BUFFERRAM, to, thislen);
 
-		/* Partial page write */
-		subpage = thislen < mtd->writesize;
-		if (subpage) {
-			memset(this->page_buf, 0xff, mtd->writesize);
-			memcpy(this->page_buf + column, buf, thislen);
-			wbuf = this->page_buf;
-		}
+			/* Partial page write */
+			subpage = thislen < mtd->writesize;
+			if (subpage) {
+				memset(this->page_buf, 0xff, mtd->writesize);
+				memcpy(this->page_buf + column, buf, thislen);
+				wbuf = this->page_buf;
+			}
 
-		this->write_bufferram(mtd, ONENAND_DATARAM, wbuf, 0, mtd->writesize);
+			this->write_bufferram(mtd, ONENAND_DATARAM, wbuf, 0, mtd->writesize);
 
-		if (oob) {
-			oobbuf = this->oob_buf;
+			if (oob) {
+				oobbuf = this->oob_buf;
 
-			/* We send data to spare ram with oobsize
-			 * to prevent byte access */
-			memset(oobbuf, 0xff, mtd->oobsize);
-			if (ops->mode == MTD_OOB_AUTO)
-				onenand_fill_auto_oob(mtd, oobbuf, oob, oobcolumn, thisooblen);
-			else
-				memcpy(oobbuf + oobcolumn, oob, thisooblen);
+				/* We send data to spare ram with oobsize
+				 * to prevent byte access */
+				memset(oobbuf, 0xff, mtd->oobsize);
+				if (ops->mode == MTD_OOB_AUTO)
+					onenand_fill_auto_oob(mtd, oobbuf, oob, oobcolumn, thisooblen);
+				else
+					memcpy(oobbuf + oobcolumn, oob, thisooblen);
 
-			oobwritten += thisooblen;
-			oob += thisooblen;
-			oobcolumn = 0;
+				oobwritten += thisooblen;
+				oob += thisooblen;
+				oobcolumn = 0;
+			} else
+				oobbuf = (u_char *) ffchars;
+
+			this->write_bufferram(mtd, ONENAND_SPARERAM, oobbuf, 0, mtd->oobsize);
 		} else
-			oobbuf = (u_char *) ffchars;
+			ONENAND_SET_NEXT_BUFFERRAM(this);
 
-		this->write_bufferram(mtd, ONENAND_SPARERAM, oobbuf, 0, mtd->oobsize);
+		/*
+		 * 2 PLANE, MLC, and Flex-OneNAND doesn't support
+		 * write-while-programe feature.
+		 */
+		if (!ONENAND_IS_2PLANE(this) && !first) {
+			ONENAND_SET_PREV_BUFFERRAM(this);
 
-		this->command(mtd, ONENAND_CMD_PROG, to, mtd->writesize);
+			ret = this->wait(mtd, FL_WRITING);
 
-		ret = this->wait(mtd, FL_WRITING);
+			/* In partial page write we don't update bufferram */
+			onenand_update_bufferram(mtd, prev, !ret && !prev_subpage);
+			if (ret) {
+				written -= prevlen;
+				printk(KERN_ERR "onenand_write_ops_nolock: write filaed %d\n", ret);
+				break;
+			}
 
-		/* In partial page write we don't update bufferram */
-		onenand_update_bufferram(mtd, to, !ret && !subpage);
-		if (ONENAND_IS_2PLANE(this)) {
-			ONENAND_SET_BUFFERRAM1(this);
-			onenand_update_bufferram(mtd, to + this->writesize, !ret && !subpage);
-		}
+			if (written == len) {
+				/* Only check verify write turn on */
+				ret = onenand_verify(mtd, buf - len, to - len, len);
+				if (ret)
+					printk(KERN_ERR "onenand_write_ops_nolock: verify failed %d\n", ret);
+				break;
+			}
 
-		if (ret) {
-			printk(KERN_ERR "onenand_write_ops_nolock: write filaed %d\n", ret);
-			break;
+			ONENAND_SET_NEXT_BUFFERRAM(this);
 		}
 
-		/* Only check verify write turn on */
-		ret = onenand_verify(mtd, buf, to, thislen);
-		if (ret) {
-			printk(KERN_ERR "onenand_write_ops_nolock: verify failed %d\n", ret);
-			break;
-		}
+		this->command(mtd, ONENAND_CMD_PROG, to, mtd->writesize);
 
-		written += thislen;
+		/*
+		 * 2 PLANE, MLC, and Flex-OneNAND wait here
+		 */
+		if (ONENAND_IS_2PLANE(this)) {
+			ret = this->wait(mtd, FL_WRITING);
 
-		if (written == len)
-			break;
+			/* In partial page write we don't update bufferram */
+			onenand_update_bufferram(mtd, to, !ret && !subpage);
+			if (ret) {
+				printk(KERN_ERR "onenand_write_ops_nolock: write filaed %d\n", ret);
+				break;
+			}
+
+			/* Only check verify write turn on */
+			ret = onenand_verify(mtd, buf, to, thislen);
+			if (ret) {
+				printk(KERN_ERR "onenand_write_ops_nolock: verify failed %d\n", ret);
+				break;
+			}
+
+			written += thislen;
+
+			if (written == len)
+				break;
+
+		} else
+			written += thislen;
 
 		column = 0;
+		prev_subpage = subpage;
+		prev = to;
+		prevlen = thislen;
 		to += thislen;
 		buf += thislen;
+		first = 0;
 	}
 
+	/* In error case, clear all bufferrams */
+	if (written != len)
+		onenand_invalidate_bufferram(mtd, 0, -1);
+
 	ops->retlen = written;
+	ops->oobretlen = oobwritten;
 
 	return ret;
 }