mtd: m25p80: Make fast read configurable via DT

Add DT property "m25p,fast-read" that signalises the particular
chip supports "fast read" opcode.

Signed-off-by: Marek Vasut <marex@denx.de>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>

2 files changed, 50 insertions, 13 deletions

diff --git a/Documentation/devicetree/bindings/mtd/m25p80.txt b/Documentation/devicetree/bindings/mtd/m25p80.txt
new file mode 100644
index 000000000000..6d3d57609470
--- /dev/null
+++ b/Documentation/devicetree/bindings/mtd/m25p80.txt
@@ -0,0 +1,29 @@
+* MTD SPI driver for ST M25Pxx (and similar) serial flash chips
+
+Required properties:
+- #address-cells, #size-cells : Must be present if the device has sub-nodes
+  representing partitions.
+- compatible : Should be the manufacturer and the name of the chip. Bear in mind
+               the DT binding is not Linux-only, but in case of Linux, see the
+               "m25p_ids" table in drivers/mtd/devices/m25p80.c for the list of
+               supported chips.
+- reg : Chip-Select number
+- spi-max-frequency : Maximum frequency of the SPI bus the chip can operate at
+
+Optional properties:
+- m25p,fast-read : Use the "fast read" opcode to read data from the chip instead
+                   of the usual "read" opcode. This opcode is not supported by
+                   all chips and support for it can not be detected at runtime.
+                   Refer to your chips' datasheet to check if this is supported
+                   by your chip.
+
+Example:
+
+        flash: m25p80@0 {
+                #address-cells = <1>;
+                #size-cells = <1>;
+                compatible = "spansion,m25p80";
+                reg = <0>;
+                spi-max-frequency = <40000000>;
+                m25p,fast-read;
+        };
diff --git a/drivers/mtd/devices/m25p80.c b/drivers/mtd/devices/m25p80.c
index 03838bab1f59..82f977456b88 100644
--- a/drivers/mtd/devices/m25p80.c
+++ b/drivers/mtd/devices/m25p80.c
@@ -73,14 +73,6 @@
 #define MAX_READY_WAIT_JIFFIES  (40 * HZ)       /* M25P16 specs 40s max chip erase */
 #define MAX_CMD_SIZE            5
 
-#ifdef CONFIG_M25PXX_USE_FAST_READ
-#define OPCODE_READ     OPCODE_FAST_READ
-#define FAST_READ_DUMMY_BYTE 1
-#else
-#define OPCODE_READ     OPCODE_NORM_READ
-#define FAST_READ_DUMMY_BYTE 0
-#endif
-
 #define JEDEC_MFR(_jedec_id)    ((_jedec_id) >> 16)
 
 /****************************************************************************/
@@ -93,6 +85,7 @@ struct m25p {
         u16                     addr_width;
         u8                      erase_opcode;
         u8                      *command;
+        bool                    fast_read;
 };
 
 static inline struct m25p *mtd_to_m25p(struct mtd_info *mtd)
@@ -342,6 +335,7 @@ 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;
+        uint8_t opcode;
 
         pr_debug("%s: %s from 0x%08x, len %zd\n", dev_name(&flash->spi->dev),
                         __func__, (u32)from, len);
@@ -354,7 +348,7 @@ static int m25p80_read(struct mtd_info *mtd, loff_t from, size_t len,
          * Should add 1 byte DUMMY_BYTE.
          */
         t[0].tx_buf = flash->command;
-        t[0].len = m25p_cmdsz(flash) + FAST_READ_DUMMY_BYTE;
+        t[0].len = m25p_cmdsz(flash) + (flash->fast_read ? 1 : 0);
         spi_message_add_tail(&t[0], &m);
 
         t[1].rx_buf = buf;
@@ -376,12 +370,14 @@ 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;
+        opcode = flash->fast_read ? OPCODE_FAST_READ : OPCODE_NORM_READ;
+        flash->command[0] = opcode;
         m25p_addr2cmd(flash, from, flash->command);
 
         spi_sync(flash->spi, &m);
 
-        *retlen = m.actual_length - m25p_cmdsz(flash) - FAST_READ_DUMMY_BYTE;
+        *retlen = m.actual_length - m25p_cmdsz(flash) -
+                        (flash->fast_read ? 1 : 0);
 
         mutex_unlock(&flash->lock);
 
@@ -809,9 +805,10 @@ static int __devinit m25p_probe(struct spi_device *spi)
         struct flash_info               *info;
         unsigned                        i;
         struct mtd_part_parser_data     ppdata;
+        struct device_node __maybe_unused *np = spi->dev.of_node;
 
 #ifdef CONFIG_MTD_OF_PARTS
-        if (!of_device_is_available(spi->dev.of_node))
+        if (!of_device_is_available(np))
                 return -ENODEV;
 #endif
 
@@ -863,7 +860,8 @@ static int __devinit m25p_probe(struct spi_device *spi)
         flash = kzalloc(sizeof *flash, GFP_KERNEL);
         if (!flash)
                 return -ENOMEM;
-        flash->command = kmalloc(MAX_CMD_SIZE + FAST_READ_DUMMY_BYTE, GFP_KERNEL);
+        flash->command = kmalloc(MAX_CMD_SIZE + (flash->fast_read ? 1 : 0),
+                                        GFP_KERNEL);
         if (!flash->command) {
                 kfree(flash);
                 return -ENOMEM;
@@ -920,6 +918,16 @@ static int __devinit m25p_probe(struct spi_device *spi)
         flash->page_size = info->page_size;
         flash->mtd.writebufsize = flash->page_size;
 
+        flash->fast_read = false;
+#ifdef CONFIG_OF
+        if (np && of_property_read_bool(np, "m25p,fast-read"))
+                flash->fast_read = true;
+#endif
+
+#ifdef CONFIG_M25PXX_USE_FAST_READ
+        flash->fast_read = true;
+#endif
+
         if (info->addr_width)
                 flash->addr_width = info->addr_width;
         else {