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>

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index c796d0e4039a7d3de41edef46a299874e15babb7..ed49a1d634b04487998c0296ecdaf681e9d4da3f 100644 (file)
--- 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 9e0c93c44bef613100f12bde08145ab88fd2b69e..8f67b15816836a1127fddae062c1ad76774e4534 100644 (file)
--- 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;