misc: eeprom_93xx46: Add quirks to support Atmel AT93C46D device.

Atmel devices in this family have some quirks not found in other similar
chips - they do not support a sequential read of the entire EEPROM
contents, and the control word sent at the start of each operation
varies in bit length.

This commit adds quirk support to the driver and modifies the read
implementation to support non-sequential reads for consistency with
other misc/eeprom drivers.

Tested on a custom Freescale VF610-based platform, with an AT93C46D
device attached via dspi2.  The spi-gpio driver was used to allow the
necessary non-byte-sized transfers.

Signed-off-by: Cory Tusar <cory.tusar@pid1solutions.com>
Tested-by: Chris Healy <chris.healy@zii.aero>
Reviewed-by: Vladimir Zapolskiy <vz@mleia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/eeprom/eeprom_93xx46.c

@@ -27,6 +27,15 @@
 #define ADDR_ERAL	0x20
 #define ADDR_EWEN	0x30
 
+struct eeprom_93xx46_devtype_data {
+	unsigned int quirks;
+};
+
+static const struct eeprom_93xx46_devtype_data atmel_at93c46d_data = {
+	.quirks = EEPROM_93XX46_QUIRK_SINGLE_WORD_READ |
+		  EEPROM_93XX46_QUIRK_INSTRUCTION_LENGTH,
+};
+
 struct eeprom_93xx46_dev {
 	struct spi_device *spi;
 	struct eeprom_93xx46_platform_data *pdata;
@@ -35,6 +44,16 @@ struct eeprom_93xx46_dev {
 	int addrlen;
 };
 
+static inline bool has_quirk_single_word_read(struct eeprom_93xx46_dev *edev)
+{
+	return edev->pdata->quirks & EEPROM_93XX46_QUIRK_SINGLE_WORD_READ;
+}
+
+static inline bool has_quirk_instruction_length(struct eeprom_93xx46_dev *edev)
+{
+	return edev->pdata->quirks & EEPROM_93XX46_QUIRK_INSTRUCTION_LENGTH;
+}
+
 static ssize_t
 eeprom_93xx46_bin_read(struct file *filp, struct kobject *kobj,
 		       struct bin_attribute *bin_attr,
@@ -42,58 +61,73 @@ eeprom_93xx46_bin_read(struct file *filp, struct kobject *kobj,
 {
 	struct eeprom_93xx46_dev *edev;
 	struct device *dev;
-	struct spi_message m;
-	struct spi_transfer t[2];
-	int bits, ret;
-	u16 cmd_addr;
+	ssize_t ret = 0;
 
 	dev = kobj_to_dev(kobj);
 	edev = dev_get_drvdata(dev);
 
-	cmd_addr = OP_READ << edev->addrlen;
+	mutex_lock(&edev->lock);
 
-	if (edev->addrlen == 7) {
-		cmd_addr |= off & 0x7f;
-		bits = 10;
-	} else {
-		cmd_addr |= (off >> 1) & 0x3f;
-		bits = 9;
-	}
+	if (edev->pdata->prepare)
+		edev->pdata->prepare(edev);
 
-	dev_dbg(&edev->spi->dev, "read cmd 0x%x, %d Hz\n",
-		cmd_addr, edev->spi->max_speed_hz);
+	while (count) {
+		struct spi_message m;
+		struct spi_transfer t[2] = { { 0 } };
+		u16 cmd_addr = OP_READ << edev->addrlen;
+		size_t nbytes = count;
+		int bits;
+		int err;
+
+		if (edev->addrlen == 7) {
+			cmd_addr |= off & 0x7f;
+			bits = 10;
+			if (has_quirk_single_word_read(edev))
+				nbytes = 1;
+		} else {
+			cmd_addr |= (off >> 1) & 0x3f;
+			bits = 9;
+			if (has_quirk_single_word_read(edev))
+				nbytes = 2;
+		}
 
-	spi_message_init(&m);
-	memset(t, 0, sizeof(t));
+		dev_dbg(&edev->spi->dev, "read cmd 0x%x, %d Hz\n",
+			cmd_addr, edev->spi->max_speed_hz);
 
-	t[0].tx_buf = (char *)&cmd_addr;
-	t[0].len = 2;
-	t[0].bits_per_word = bits;
-	spi_message_add_tail(&t[0], &m);
+		spi_message_init(&m);
 
-	t[1].rx_buf = buf;
-	t[1].len = count;
-	t[1].bits_per_word = 8;
-	spi_message_add_tail(&t[1], &m);
+		t[0].tx_buf = (char *)&cmd_addr;
+		t[0].len = 2;
+		t[0].bits_per_word = bits;
+		spi_message_add_tail(&t[0], &m);
 
-	mutex_lock(&edev->lock);
+		t[1].rx_buf = buf;
+		t[1].len = count;
+		t[1].bits_per_word = 8;
+		spi_message_add_tail(&t[1], &m);
 
-	if (edev->pdata->prepare)
-		edev->pdata->prepare(edev);
+		err = spi_sync(edev->spi, &m);
+		/* have to wait at least Tcsl ns */
+		ndelay(250);
 
-	ret = spi_sync(edev->spi, &m);
-	/* have to wait at least Tcsl ns */
-	ndelay(250);
-	if (ret) {
-		dev_err(&edev->spi->dev, "read %zu bytes at %d: err. %d\n",
-			count, (int)off, ret);
+		if (err) {
+			dev_err(&edev->spi->dev, "read %zu bytes at %d: err. %d\n",
+				nbytes, (int)off, err);
+			ret = err;
+			break;
+		}
+
+		buf += nbytes;
+		off += nbytes;
+		count -= nbytes;
+		ret += nbytes;
 	}
 
 	if (edev->pdata->finish)
 		edev->pdata->finish(edev);
 
 	mutex_unlock(&edev->lock);
-	return ret ? : count;
+	return ret;
 }
 
 static int eeprom_93xx46_ew(struct eeprom_93xx46_dev *edev, int is_on)
@@ -112,7 +146,13 @@ static int eeprom_93xx46_ew(struct eeprom_93xx46_dev *edev, int is_on)
 		bits = 9;
 	}
 
-	dev_dbg(&edev->spi->dev, "ew cmd 0x%04x\n", cmd_addr);
+	if (has_quirk_instruction_length(edev)) {
+		cmd_addr <<= 2;
+		bits += 2;
+	}
+
+	dev_dbg(&edev->spi->dev, "ew%s cmd 0x%04x, %d bits\n",
+			is_on ? "en" : "ds", cmd_addr, bits);
 
 	spi_message_init(&m);
 	memset(&t, 0, sizeof(t));
@@ -247,6 +287,13 @@ static int eeprom_93xx46_eral(struct eeprom_93xx46_dev *edev)
 		bits = 9;
 	}
 
+	if (has_quirk_instruction_length(edev)) {
+		cmd_addr <<= 2;
+		bits += 2;
+	}
+
+	dev_dbg(&edev->spi->dev, "eral cmd 0x%04x, %d bits\n", cmd_addr, bits);
+
 	spi_message_init(&m);
 	memset(&t, 0, sizeof(t));
 
@@ -298,12 +345,15 @@ static DEVICE_ATTR(erase, S_IWUSR, NULL, eeprom_93xx46_store_erase);
 
 static const struct of_device_id eeprom_93xx46_of_table[] = {
 	{ .compatible = "eeprom-93xx46", },
+	{ .compatible = "atmel,at93c46d", .data = &atmel_at93c46d_data, },
 	{}
 };
 MODULE_DEVICE_TABLE(of, eeprom_93xx46_of_table);
 
 static int eeprom_93xx46_probe_dt(struct spi_device *spi)
 {
+	const struct of_device_id *of_id =
+		of_match_device(eeprom_93xx46_of_table, &spi->dev);
 	struct device_node *np = spi->dev.of_node;
 	struct eeprom_93xx46_platform_data *pd;
 	u32 tmp;
@@ -331,6 +381,12 @@ static int eeprom_93xx46_probe_dt(struct spi_device *spi)
 	if (of_property_read_bool(np, "read-only"))
 		pd->flags |= EE_READONLY;
 
+	if (of_id->data) {
+		const struct eeprom_93xx46_devtype_data *data = of_id->data;
+
+		pd->quirks = data->quirks;
+	}
+
 	spi->dev.platform_data = pd;
 
 	return 0;

include/linux/eeprom_93xx46.h

@@ -9,6 +9,12 @@ struct eeprom_93xx46_platform_data {
 #define EE_ADDR16	0x02		/* 16 bit addr. cfg */
 #define EE_READONLY	0x08		/* forbid writing */
 
+	unsigned int	quirks;
+/* Single word read transfers only; no sequential read. */
+#define EEPROM_93XX46_QUIRK_SINGLE_WORD_READ		(1 << 0)
+/* Instructions such as EWEN are (addrlen + 2) in length. */
+#define EEPROM_93XX46_QUIRK_INSTRUCTION_LENGTH		(1 << 1)
+
 	/*
 	 * optional hooks to control additional logic
 	 * before and after spi transfer.