[PATCH 4/6] mtd: m25p80: change the read function to read page by page

[Mingkai Hu <Mingkai.hu@freescale.com>]

For Freescale's eSPI controller, the max transaction length one time
is limitted by the SPCOM[TRANSLEN] field which is 0x10000. When used
mkfs.ext2 command to create ext2 filesystem on the flash, the read
length will exceed the max value of the SPCOM[TRANSLEN] field, so
change the read function to read page by page.

For other SPI flash driver, also needed to change the read function
if used the eSPI controller.

Signed-off-by: Mingkai Hu <Mingkai.hu@freescale.com>
---
 drivers/mtd/devices/m25p80.c |   18 ++++++++++++++----
 1 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/devices/m25p80.c b/drivers/mtd/devices/m25p80.c
index 81e49a9..6cbe6b1 100644
--- a/drivers/mtd/devices/m25p80.c
+++ b/drivers/mtd/devices/m25p80.c
@@ -317,6 +317,7 @@ static int m25p80_read(struct mtd_info *mtd, loff_t from, size_t len,
 	struct m25p *flash = mtd_to_m25p(mtd);
 	struct spi_transfer t[2];
 	struct spi_message m;
+	u32 i, page_size = 0;
 
 	DEBUG(MTD_DEBUG_LEVEL2, "%s: %s %s 0x%08x, len %zd\n",
 			dev_name(&flash->spi->dev), __func__, "from",
@@ -341,7 +342,6 @@ static int m25p80_read(struct mtd_info *mtd, loff_t from, size_t len,
 	spi_message_add_tail(&t[0], &m);
 
 	t[1].rx_buf = buf;
-	t[1].len = len;
 	spi_message_add_tail(&t[1], &m);
 
 	/* Byte count starts at zero. */
@@ -364,11 +364,21 @@ static int m25p80_read(struct mtd_info *mtd, loff_t from, size_t len,
 
 	/* Set up the write data buffer. */
 	flash->command[0] = OPCODE_READ;
-	m25p_addr2cmd(flash, from, flash->command);
 
-	spi_sync(flash->spi, &m);
+	for (i = page_size; i < len; i += page_size) {
+		page_size = len - i;
+		if (page_size > flash->page_size)
+			page_size = flash->page_size;
 
-	*retlen = m.actual_length - m25p_cmdsz(flash) - FAST_READ_DUMMY_BYTE;
+		m25p_addr2cmd(flash, from + i, flash->command);
+		t[1].len = page_size;
+		t[1].rx_buf = buf + i;
+
+		spi_sync(flash->spi, &m);
+
+		*retlen += m.actual_length - m25p_cmdsz(flash)
+			- FAST_READ_DUMMY_BYTE;
+	}
 
 	mutex_unlock(&flash->lock);
 
-- 
1.6.4