1 files changed, 236 insertions, 0 deletions
diff --git a/drivers/mtd/devices/mchp23k256.c b/drivers/mtd/devices/mchp23k256.c
new file mode 100644
index 0000000..8956b7d
--- /dev/null
+++ b/drivers/mtd/devices/mchp23k256.c
@@ -0,0 +1,236 @@
+/*
+ * mchp23k256.c
+ *
+ * Driver for Microchip 23k256 SPI RAM chips
+ *
+ * Copyright © 2016 Andrew Lunn <andrew@lunn.ch>
+ *
+ * This code is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mtd/partitions.h>
+#include <linux/mutex.h>
+#include <linux/sched.h>
+#include <linux/sizes.h>
+#include <linux/spi/flash.h>
+#include <linux/spi/spi.h>
+#include <linux/of_device.h>
+
+#define MAX_CMD_SIZE		4
+
+struct mchp23_caps {
+	u8 addr_width;
+	unsigned int size;
+};
+
+struct mchp23k256_flash {
+	struct spi_device	*spi;
+	struct mutex		lock;
+	struct mtd_info		mtd;
+	const struct mchp23_caps	*caps;
+};
+
+#define MCHP23K256_CMD_WRITE_STATUS	0x01
+#define MCHP23K256_CMD_WRITE		0x02
+#define MCHP23K256_CMD_READ		0x03
+#define MCHP23K256_MODE_SEQ		BIT(6)
+
+#define to_mchp23k256_flash(x) container_of(x, struct mchp23k256_flash, mtd)
+
+static void mchp23k256_addr2cmd(struct mchp23k256_flash *flash,
+				unsigned int addr, u8 *cmd)
+{
+	int i;
+
+	/*
+	 * Address is sent in big endian (MSB first) and we skip
+	 * the first entry of the cmd array which contains the cmd
+	 * opcode.
+	 */
+	for (i = flash->caps->addr_width; i > 0; i--, addr >>= 8)
+		cmd[i] = addr;
+}
+
+static int mchp23k256_cmdsz(struct mchp23k256_flash *flash)
+{
+	return 1 + flash->caps->addr_width;
+}
+
+static int mchp23k256_write(struct mtd_info *mtd, loff_t to, size_t len,
+			    size_t *retlen, const unsigned char *buf)
+{
+	struct mchp23k256_flash *flash = to_mchp23k256_flash(mtd);
+	struct spi_transfer transfer[2] = {};
+	struct spi_message message;
+	unsigned char command[MAX_CMD_SIZE];
+
+	spi_message_init(&message);
+
+	command[0] = MCHP23K256_CMD_WRITE;
+	mchp23k256_addr2cmd(flash, to, command);
+
+	transfer[0].tx_buf = command;
+	transfer[0].len = mchp23k256_cmdsz(flash);
+	spi_message_add_tail(&transfer[0], &message);
+
+	transfer[1].tx_buf = buf;
+	transfer[1].len = len;
+	spi_message_add_tail(&transfer[1], &message);
+
+	mutex_lock(&flash->lock);
+
+	spi_sync(flash->spi, &message);
+
+	if (retlen && message.actual_length > sizeof(command))
+		*retlen += message.actual_length - sizeof(command);
+
+	mutex_unlock(&flash->lock);
+	return 0;
+}
+
+static int mchp23k256_read(struct mtd_info *mtd, loff_t from, size_t len,
+			   size_t *retlen, unsigned char *buf)
+{
+	struct mchp23k256_flash *flash = to_mchp23k256_flash(mtd);
+	struct spi_transfer transfer[2] = {};
+	struct spi_message message;
+	unsigned char command[MAX_CMD_SIZE];
+
+	spi_message_init(&message);
+
+	memset(&transfer, 0, sizeof(transfer));
+	command[0] = MCHP23K256_CMD_READ;
+	mchp23k256_addr2cmd(flash, from, command);
+
+	transfer[0].tx_buf = command;
+	transfer[0].len = mchp23k256_cmdsz(flash);
+	spi_message_add_tail(&transfer[0], &message);
+
+	transfer[1].rx_buf = buf;
+	transfer[1].len = len;
+	spi_message_add_tail(&transfer[1], &message);
+
+	mutex_lock(&flash->lock);
+
+	spi_sync(flash->spi, &message);
+
+	if (retlen && message.actual_length > sizeof(command))
+		*retlen += message.actual_length - sizeof(command);
+
+	mutex_unlock(&flash->lock);
+	return 0;
+}
+
+/*
+ * Set the device into sequential mode. This allows read/writes to the
+ * entire SRAM in a single operation
+ */
+static int mchp23k256_set_mode(struct spi_device *spi)
+{
+	struct spi_transfer transfer = {};
+	struct spi_message message;
+	unsigned char command[2];
+
+	spi_message_init(&message);
+
+	command[0] = MCHP23K256_CMD_WRITE_STATUS;
+	command[1] = MCHP23K256_MODE_SEQ;
+
+	transfer.tx_buf = command;
+	transfer.len = sizeof(command);
+	spi_message_add_tail(&transfer, &message);
+
+	return spi_sync(spi, &message);
+}
+
+static const struct mchp23_caps mchp23k256_caps = {
+	.size = SZ_32K,
+	.addr_width = 2,
+};
+
+static const struct mchp23_caps mchp23lcv1024_caps = {
+	.size = SZ_128K,
+	.addr_width = 3,
+};
+
+static int mchp23k256_probe(struct spi_device *spi)
+{
+	struct mchp23k256_flash *flash;
+	struct flash_platform_data *data;
+	int err;
+
+	flash = devm_kzalloc(&spi->dev, sizeof(*flash), GFP_KERNEL);
+	if (!flash)
+		return -ENOMEM;
+
+	flash->spi = spi;
+	mutex_init(&flash->lock);
+	spi_set_drvdata(spi, flash);
+
+	err = mchp23k256_set_mode(spi);
+	if (err)
+		return err;
+
+	data = dev_get_platdata(&spi->dev);
+
+	flash->caps = of_device_get_match_data(&spi->dev);
+	if (!flash->caps)
+		flash->caps = &mchp23k256_caps;
+
+	mtd_set_of_node(&flash->mtd, spi->dev.of_node);
+	flash->mtd.dev.parent	= &spi->dev;
+	flash->mtd.type		= MTD_RAM;
+	flash->mtd.flags	= MTD_CAP_RAM;
+	flash->mtd.writesize	= 1;
+	flash->mtd.size		= flash->caps->size;
+	flash->mtd._read	= mchp23k256_read;
+	flash->mtd._write	= mchp23k256_write;
+
+	err = mtd_device_register(&flash->mtd, data ? data->parts : NULL,
+				  data ? data->nr_parts : 0);
+	if (err)
+		return err;
+
+	return 0;
+}
+
+static int mchp23k256_remove(struct spi_device *spi)
+{
+	struct mchp23k256_flash *flash = spi_get_drvdata(spi);
+
+	return mtd_device_unregister(&flash->mtd);
+}
+
+static const struct of_device_id mchp23k256_of_table[] = {
+	{
+		.compatible = "microchip,mchp23k256",
+		.data = &mchp23k256_caps,
+	},
+	{
+		.compatible = "microchip,mchp23lcv1024",
+		.data = &mchp23lcv1024_caps,
+	},
+	{}
+};
+MODULE_DEVICE_TABLE(of, mchp23k256_of_table);
+
+static struct spi_driver mchp23k256_driver = {
+	.driver = {
+		.name	= "mchp23k256",
+		.of_match_table = of_match_ptr(mchp23k256_of_table),
+	},
+	.probe		= mchp23k256_probe,
+	.remove		= mchp23k256_remove,
+};
+
+module_spi_driver(mchp23k256_driver);
+
+MODULE_DESCRIPTION("MTD SPI driver for MCHP23K256 RAM chips");
+MODULE_AUTHOR("Andrew Lunn <andre@lunn.ch>");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("spi:mchp23k256");