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

[Linux-MTD Mailing List]

Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=477544c62a84d3bacd9f90ba75ffc16c04d78071
Commit:     477544c62a84d3bacd9f90ba75ffc16c04d78071
Parent:     3deb9979c7319bc7846d1aac528a9db85162960a
Author:     Masahiro Yamada <yamada.masahiro at socionext.com>
AuthorDate: Thu Mar 30 17:15:05 2017 +0900
Committer:  Boris Brezillon <boris.brezillon at free-electrons.com>
CommitDate: Tue Apr 25 14:18:38 2017 +0200

    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 at socionext.com>
    Signed-off-by: Boris Brezillon <boris.brezillon at free-electrons.com>
---
 drivers/mtd/nand/nand_base.c | 10 ++++++++--
 include/linux/mtd/nand.h     |  2 ++
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index c796d0e..ed49a1d 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 9e0c93c..8f67b15 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;