mtd: nand: allow drivers to request minimum alignment for passed buffer

In some cases, nand_do_{read,write}_ops is passed with unaligned
ops->datbuf.  Drivers using DMA will be unhappy about unaligned
buffer.

The new struct member, buf_align, represents the minimum alignment
the driver require for the buffer.  If the buffer passed from the
upper MTD layer does not have enough alignment, nand_do_*_ops will
use bufpoi.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

2 files changed, 10 insertions, 2 deletions

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index c796d0e4039a..ed49a1d634b0 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -1954,7 +1954,9 @@ static int nand_do_read_ops(struct mtd_info *mtd, loff_t from,
                 if (!aligned)
                         use_bufpoi = 1;
                 else if (chip->options & NAND_USE_BOUNCE_BUFFER)
-                        use_bufpoi = !virt_addr_valid(buf);
+                        use_bufpoi = !virt_addr_valid(buf) ||
+                                     !IS_ALIGNED((unsigned long)buf,
+                                                 chip->buf_align);
                 else
                         use_bufpoi = 0;
 
@@ -2810,7 +2812,9 @@ static int nand_do_write_ops(struct mtd_info *mtd, loff_t to,
                 if (part_pagewr)
                         use_bufpoi = 1;
                 else if (chip->options & NAND_USE_BOUNCE_BUFFER)
-                        use_bufpoi = !virt_addr_valid(buf);
+                        use_bufpoi = !virt_addr_valid(buf) ||
+                                     !IS_ALIGNED((unsigned long)buf,
+                                                 chip->buf_align);
                 else
                         use_bufpoi = 0;
 
@@ -3429,6 +3433,8 @@ static void nand_set_defaults(struct nand_chip *chip)
                 nand_hw_control_init(chip->controller);
         }
 
+        if (!chip->buf_align)
+                chip->buf_align = 1;
 }
 
 /* Sanitize ONFI strings so we can safely print them */
diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
index 9e0c93c44bef..8f67b1581683 100644
--- a/include/linux/mtd/nand.h
+++ b/include/linux/mtd/nand.h
@@ -755,6 +755,7 @@ struct nand_manufacturer_ops {
  *                      setting the read-retry mode. Mostly needed for MLC NAND.
  * @ecc:                [BOARDSPECIFIC] ECC control structure
  * @buffers:            buffer structure for read/write
+ * @buf_align:          minimum buffer alignment required by a platform
  * @hwcontrol:          platform-specific hardware control structure
  * @erase:              [REPLACEABLE] erase function
  * @scan_bbt:           [REPLACEABLE] function to scan bad block table
@@ -905,6 +906,7 @@ struct nand_chip {
 
         struct nand_ecc_ctrl ecc;
         struct nand_buffers *buffers;
+        unsigned long buf_align;
         struct nand_hw_control hwcontrol;
 
         uint8_t *bbt;