[PATCH] Add erase interface for AT25 driver.

[Joe Burmeister <joe.burmeister@devtank.co.uk>]

Signed-off-by: Joe Burmeister <joe.burmeister@devtank.co.uk>
---
 drivers/misc/eeprom/at25.c | 75 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 74 insertions(+), 1 deletion(-)

diff --git a/drivers/misc/eeprom/at25.c b/drivers/misc/eeprom/at25.c
index 99de6939cd5a..b1fb3bfd935d 100644
--- a/drivers/misc/eeprom/at25.c
+++ b/drivers/misc/eeprom/at25.c
@@ -43,6 +43,7 @@ struct at25_data {
 #define	AT25_WRSR	0x01		/* write status register */
 #define	AT25_READ	0x03		/* read byte(s) */
 #define	AT25_WRITE	0x02		/* write byte(s)/sector */
+#define AT25_CHIP_ERASE	0x62		/* Erase whole chip */
 
 #define	AT25_SR_nRDY	0x01		/* nRDY = write-in-progress */
 #define	AT25_SR_WEN	0x02		/* write enable (latched) */
@@ -52,6 +53,7 @@ struct at25_data {
 
 #define	AT25_INSTR_BIT3	0x08		/* Additional address bit in instr */
 
+
 #define EE_MAXADDRLEN	3		/* 24 bit addresses, up to 2 MBytes */
 
 /* Specs often allow 5 msec for a page write, sometimes 20 msec;
@@ -59,6 +61,8 @@ struct at25_data {
  */
 #define	EE_TIMEOUT	25
 
+#define ERASE_TIMEOUT 2020
+
 /*-------------------------------------------------------------------------*/
 
 #define	io_limit	PAGE_SIZE	/* bytes */
@@ -304,6 +308,71 @@ static int at25_fw_to_chip(struct device *dev, struct spi_eeprom *chip)
 	return 0;
 }
 
+static void _eeprom_at25_store_erase_locked(struct at25_data *at25)
+{
+	unsigned long	timeout, retries;
+	int				sr, status;
+	u8	cp;
+
+	cp = AT25_WREN;
+	status = spi_write(at25->spi, &cp, 1);
+	if (status < 0) {
+		dev_dbg(&at25->spi->dev, "ERASE WREN --> %d\n", status);
+		return;
+	}
+	cp = AT25_CHIP_ERASE;
+	status = spi_write(at25->spi, &cp, 1);
+	if (status < 0) {
+		dev_dbg(&at25->spi->dev, "CHIP_ERASE --> %d\n", status);
+		return;
+	}
+	/* Wait for non-busy status */
+	timeout = jiffies + msecs_to_jiffies(ERASE_TIMEOUT);
+	retries = 0;
+	do {
+		sr = spi_w8r8(at25->spi, AT25_RDSR);
+		if (sr < 0 || (sr & AT25_SR_nRDY)) {
+			dev_dbg(&at25->spi->dev,
+				"rdsr --> %d (%02x)\n", sr, sr);
+			/* at HZ=100, this is sloooow */
+			msleep(1);
+			continue;
+		}
+		if (!(sr & AT25_SR_nRDY))
+			return;
+	} while (retries++ < 200 || time_before_eq(jiffies, timeout));
+
+	if ((sr < 0) || (sr & AT25_SR_nRDY)) {
+		dev_err(&at25->spi->dev,
+			"chip erase, timeout after %u msecs\n",
+			jiffies_to_msecs(jiffies -
+				(timeout - ERASE_TIMEOUT)));
+		status = -ETIMEDOUT;
+		return;
+	}
+}
+
+
+static ssize_t eeprom_at25_store_erase(struct device *dev,
+					 struct device_attribute *attr,
+					 const char *buf, size_t count)
+{
+	struct at25_data *at25 = dev_get_drvdata(dev);
+	int erase = 0;
+
+	sscanf(buf, "%d", &erase);
+	if (erase) {
+		mutex_lock(&at25->lock);
+		_eeprom_at25_store_erase_locked(at25);
+		mutex_unlock(&at25->lock);
+	}
+
+	return count;
+}
+
+static DEVICE_ATTR(erase, S_IWUSR, NULL, eeprom_at25_store_erase);
+
+
 static int at25_probe(struct spi_device *spi)
 {
 	struct at25_data	*at25 = NULL;
@@ -376,11 +445,15 @@ static int at25_probe(struct spi_device *spi)
 		at25->chip.name,
 		(chip.flags & EE_READONLY) ? " (readonly)" : "",
 		at25->chip.page_size);
+
+        if (!(chip.flags & EE_READONLY))
+            if (device_create_file(&spi->dev, &dev_attr_erase))
+                dev_err(&spi->dev, "can't create erase interface\n");
+
 	return 0;
 }
 
 /*-------------------------------------------------------------------------*/
-
 static const struct of_device_id at25_of_match[] = {
 	{ .compatible = "atmel,at25", },
 	{ }
-- 
2.20.1