[MTD] OneNAND: Implement read-while-load

Read-while-load enables higher performance read operations.

Signed-off-by: Adrian Hunter <ext-adrian.hunter@nokia.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>

2 files changed, 43 insertions, 32 deletions

diff --git a/drivers/mtd/onenand/onenand_base.c b/drivers/mtd/onenand/onenand_base.c
index e80857b3bb83..abbe160b4309 100644
--- a/drivers/mtd/onenand/onenand_base.c
+++ b/drivers/mtd/onenand/onenand_base.c
@@ -727,40 +727,47 @@ static int onenand_read(struct mtd_info *mtd, loff_t from, size_t len,
         /* TODO handling oob */
 
         stats = mtd->ecc_stats;
-        while (read < len) {
-                cond_resched();
-
-                thislen = min_t(int, mtd->writesize, len - read);
-
-                column = from & (mtd->writesize - 1);
-                if (column + thislen > mtd->writesize)
-                        thislen = mtd->writesize - column;
-
-                if (!onenand_check_bufferram(mtd, from)) {
-                        this->command(mtd, ONENAND_CMD_READ, from, mtd->writesize);
-
-                        ret = this->wait(mtd, FL_READING);
-                        /* First copy data and check return value for ECC handling */
-                        onenand_update_bufferram(mtd, from, !ret);
-                }
-
-                this->read_bufferram(mtd, ONENAND_DATARAM, buf, column, thislen);
 
-                if (ret) {
-                        DEBUG(MTD_DEBUG_LEVEL0, "onenand_read: read failed = %d\n", ret);
-                        goto out;
-                }
+        /* Read-while-load method */
+
+        /* Do first load to bufferRAM */
+        if (read < len) {
+                if (!onenand_check_bufferram(mtd, from)) {
+                        this->command(mtd, ONENAND_CMD_READ, from, mtd->writesize);
+                        ret = this->wait(mtd, FL_READING);
+                        onenand_update_bufferram(mtd, from, !ret);
+                }
+        }
+
+        thislen = min_t(int, mtd->writesize, len - read);
+        column = from & (mtd->writesize - 1);
+        if (column + thislen > mtd->writesize)
+                thislen = mtd->writesize - column;
+
+        while (!ret) {
+                /* If there is more to load then start next load */
+                from += thislen;
+                if (read + thislen < len) {
+                        this->command(mtd, ONENAND_CMD_READ, from, mtd->writesize);
+                        ONENAND_SET_PREV_BUFFERRAM(this);
+                }
+                /* While load is going, read from last bufferRAM */
+                this->read_bufferram(mtd, ONENAND_DATARAM, buf, column, thislen);
+                /* See if we are done */
+                read += thislen;
+                if (read == len)
+                        break;
+                /* Set up for next read from bufferRAM */
+                ONENAND_SET_NEXT_BUFFERRAM(this);
+                buf += thislen;
+                thislen = min_t(int, mtd->writesize, len - read);
+                column = 0;
+                cond_resched();
+                /* Now wait for load */
+                ret = this->wait(mtd, FL_READING);
+                onenand_update_bufferram(mtd, from, !ret);
+        }
 
-                read += thislen;
-
-                if (read == len)
-                        break;
-
-                from += thislen;
-                buf += thislen;
-        }
-
-out:
         /* Deselect and wake up anyone waiting on the device */
         onenand_release_device(mtd);
 
@@ -774,6 +781,9 @@ out:
         if (mtd->ecc_stats.failed - stats.failed)
                 return -EBADMSG;
 
+        if (ret)
+                return ret;
+
         return mtd->ecc_stats.corrected - stats.corrected ? -EUCLEAN : 0;
 }
 
diff --git a/include/linux/mtd/onenand.h b/include/linux/mtd/onenand.h
index fe3500d7d4bb..f775a7af3890 100644
--- a/include/linux/mtd/onenand.h
+++ b/include/linux/mtd/onenand.h
@@ -143,6 +143,7 @@ struct onenand_chip {
 #define ONENAND_CURRENT_BUFFERRAM(this)         (this->bufferram_index)
 #define ONENAND_NEXT_BUFFERRAM(this)            (this->bufferram_index ^ 1)
 #define ONENAND_SET_NEXT_BUFFERRAM(this)        (this->bufferram_index ^= 1)
+#define ONENAND_SET_PREV_BUFFERRAM(this)        (this->bufferram_index ^= 1)
 
 #define ONENAND_GET_SYS_CFG1(this)                                      \
         (this->read_word(this->base + ONENAND_REG_SYS_CFG1))