mtd: nand: Add support to use nand_base poi databuf as bounce buffer

nand_base can be passed a kmap()'d buffers from highmem by
filesystems like jffs2. This results in failure to map the
physical address of the DMA buffer on various contoller
driver on different platforms. This change adds a chip option
to use preallocated databuf as bounce buffers used in
nand_do_read_ops() and nand_do_write_ops().
This allows for specific nand controller driver to set this
option as needed.

Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

1 files changed, 31 insertions, 6 deletions

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index 7853b9b0a05e..1b844b8c621f 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -37,6 +37,7 @@
 #include <linux/err.h>
 #include <linux/sched.h>
 #include <linux/slab.h>
+#include <linux/mm.h>
 #include <linux/types.h>
 #include <linux/mtd/mtd.h>
 #include <linux/mtd/nand.h>
@@ -1500,6 +1501,7 @@ static int nand_do_read_ops(struct mtd_info *mtd, loff_t from,
                 mtd->oobavail : mtd->oobsize;
 
         uint8_t *bufpoi, *oob, *buf;
+        int use_bufpoi;
         unsigned int max_bitflips = 0;
         int retry_mode = 0;
         bool ecc_fail = false;
@@ -1522,9 +1524,20 @@ static int nand_do_read_ops(struct mtd_info *mtd, loff_t from,
                 bytes = min(mtd->writesize - col, readlen);
                 aligned = (bytes == mtd->writesize);
 
+                if (!aligned)
+                        use_bufpoi = 1;
+                else if (chip->options & NAND_USE_BOUNCE_BUFFER)
+                        use_bufpoi = !virt_addr_valid(buf);
+                else
+                        use_bufpoi = 0;
+
                 /* Is the current page in the buffer? */
                 if (realpage != chip->pagebuf || oob) {
-                        bufpoi = aligned ? buf : chip->buffers->databuf;
+                        bufpoi = use_bufpoi ? chip->buffers->databuf : buf;
+
+                        if (use_bufpoi && aligned)
+                                pr_debug("%s: using read bounce buffer for buf@%p\n",
+                                                 __func__, buf);
 
 read_retry:
                         chip->cmdfunc(mtd, NAND_CMD_READ0, 0x00, page);
@@ -1546,7 +1559,7 @@ read_retry:
                                 ret = chip->ecc.read_page(mtd, chip, bufpoi,
                                                           oob_required, page);
                         if (ret < 0) {
-                                if (!aligned)
+                                if (use_bufpoi)
                                         /* Invalidate page cache */
                                         chip->pagebuf = -1;
                                 break;
@@ -1555,7 +1568,7 @@ read_retry:
                         max_bitflips = max_t(unsigned int, max_bitflips, ret);
 
                         /* Transfer not aligned data */
-                        if (!aligned) {
+                        if (use_bufpoi) {
                                 if (!NAND_HAS_SUBPAGE_READ(chip) && !oob &&
                                     !(mtd->ecc_stats.failed - ecc_failures) &&
                                     (ops->mode != MTD_OPS_RAW)) {
@@ -2375,11 +2388,23 @@ static int nand_do_write_ops(struct mtd_info *mtd, loff_t to,
                 int bytes = mtd->writesize;
                 int cached = writelen > bytes && page != blockmask;
                 uint8_t *wbuf = buf;
+                int use_bufpoi;
+                int part_pagewr = (column || writelen < (mtd->writesize - 1));
+
+                if (part_pagewr)
+                        use_bufpoi = 1;
+                else if (chip->options & NAND_USE_BOUNCE_BUFFER)
+                        use_bufpoi = !virt_addr_valid(buf);
+                else
+                        use_bufpoi = 0;
 
-                /* Partial page write? */
-                if (unlikely(column || writelen < (mtd->writesize - 1))) {
+                /* Partial page write?, or need to use bounce buffer */
+                if (use_bufpoi) {
+                        pr_debug("%s: using write bounce buffer for buf@%p\n",
+                                         __func__, buf);
                         cached = 0;
-                        bytes = min_t(int, bytes - column, (int) writelen);
+                        if (part_pagewr)
+                                bytes = min_t(int, bytes - column, writelen);
                         chip->pagebuf = -1;
                         memset(chip->buffers->databuf, 0xff, mtd->writesize);
                         memcpy(&chip->buffers->databuf[column], buf, bytes);