From 5fb4e8d7287ac8fcb33aae8b1e9e22c5a3c392bd Mon Sep 17 00:00:00 2001
From: Jonas Gorski <jonas.gorski@gmail.com>
Date: Thu, 10 Nov 2011 17:33:40 +0100
Subject: [PATCH 51/79] MTD: DEVICES: m25p80: add support for limiting reads

Signed-off-by: Jonas Gorski <jonas.gorski@gmail.com>
---
 drivers/mtd/devices/m25p80.c |   29 +++++++++++++++++++++++++++--
 include/linux/spi/flash.h    |    4 ++++
 2 files changed, 31 insertions(+), 2 deletions(-)

--- a/drivers/mtd/devices/m25p80.c
+++ b/drivers/mtd/devices/m25p80.c
@@ -115,6 +115,7 @@ struct m25p {
 	u8			program_opcode;
 	u8			*command;
 	enum read_type		flash_read;
+	int			max_transfer_len;
 };
 
 static inline struct m25p *mtd_to_m25p(struct mtd_info *mtd)
@@ -509,10 +510,9 @@ static inline unsigned int m25p80_rx_nbi
  * Read an address range from the flash chip.  The address range
  * may be any size provided it is within the physical boundaries.
  */
-static int m25p80_read(struct mtd_info *mtd, loff_t from, size_t len,
+static int __m25p80_read(struct m25p *flash, loff_t from, size_t len,
 	size_t *retlen, u_char *buf)
 {
-	struct m25p *flash = mtd_to_m25p(mtd);
 	struct spi_transfer t[2];
 	struct spi_message m;
 	uint8_t opcode;
@@ -562,6 +562,28 @@ static int m25p80_read(struct mtd_info *
 	return 0;
 }
 
+static int m25p80_read(struct mtd_info *mtd, loff_t from, size_t len,
+	size_t *retlen, u_char *buf)
+{
+	struct m25p *flash = mtd_to_m25p(mtd);
+	size_t off;
+	size_t read_len = flash->max_transfer_len;
+	size_t part_len;
+	int ret = 0;
+
+	if (!read_len)
+		return __m25p80_read(flash, from, len, retlen, buf);
+
+	*retlen = 0;
+
+	for (off = 0; off < len && !ret; off += read_len) {
+		ret = __m25p80_read(flash, from + off, min(len - off, read_len),
+				    &part_len, buf + off);
+			*retlen += part_len;
+	}
+
+	return ret;
+}
 /*
  * Write an address range to the flash chip.  Data must be written in
  * FLASH_PAGESIZE chunks.  The address range may be any size provided
@@ -1159,6 +1181,9 @@ static int m25p_probe(struct spi_device
 	if (!flash->command)
 		return -ENOMEM;
 
+	if (data)
+		flash->max_transfer_len = data->max_transfer_len;
+
 	flash->spi = spi;
 	mutex_init(&flash->lock);
 	spi_set_drvdata(spi, flash);
--- a/include/linux/spi/flash.h
+++ b/include/linux/spi/flash.h
@@ -13,6 +13,8 @@ struct mtd_part_parser_data;
  * @part_probe_types: optional list of MTD parser names to use for
  *	partitioning
  *
+ * @max_transfer_len: option maximum read/write length limitation for
+ *	SPI controllers not able to transfer any length commands.
  * Board init code (in arch/.../mach-xxx/board-yyy.c files) can
  * provide information about SPI flash parts (such as DataFlash) to
  * help set up the device and its appropriate default partitioning.
@@ -28,6 +30,8 @@ struct flash_platform_data {
 	char		*type;
 
 	const char	**part_probe_types;
+
+	unsigned int	max_transfer_len;
 	/* we'll likely add more ... use JEDEC IDs, etc */
 };