3 files changed, 193 insertions, 0 deletions

diff --git a/drivers/mtd/devices/Kconfig b/drivers/mtd/devices/Kconfig
index 58329d2dacd1..6def5445e03e 100644
--- a/drivers/mtd/devices/Kconfig
+++ b/drivers/mtd/devices/Kconfig
@@ -95,6 +95,16 @@ config MTD_M25P80
           if you want to specify device partitioning or to use a device which
           doesn't support the JEDEC ID instruction.
 
+config MTD_MCHP23K256
+        tristate "Microchip 23K256 SRAM"
+        depends on SPI_MASTER
+        help
+          This enables access to Microchip 23K256 SRAM chips, using SPI.
+
+          Set up your spi devices with the right board-specific
+          platform data, or a device tree description if you want to
+          specify device partitioning
+
 config MTD_SPEAR_SMI
         tristate "SPEAR MTD NOR Support through SMI controller"
         depends on PLAT_SPEAR
diff --git a/drivers/mtd/devices/Makefile b/drivers/mtd/devices/Makefile
index 7912d3a0ee34..f0f767624cc6 100644
--- a/drivers/mtd/devices/Makefile
+++ b/drivers/mtd/devices/Makefile
@@ -12,6 +12,7 @@ obj-$(CONFIG_MTD_LART)		+= lart.o
 obj-$(CONFIG_MTD_BLOCK2MTD)     += block2mtd.o
 obj-$(CONFIG_MTD_DATAFLASH)     += mtd_dataflash.o
 obj-$(CONFIG_MTD_M25P80)        += m25p80.o
+obj-$(CONFIG_MTD_MCHP23K256)    += mchp23k256.o
 obj-$(CONFIG_MTD_SPEAR_SMI)     += spear_smi.o
 obj-$(CONFIG_MTD_SST25L)        += sst25l.o
 obj-$(CONFIG_MTD_BCM47XXSFLASH) += bcm47xxsflash.o
diff --git a/drivers/mtd/devices/mchp23k256.c b/drivers/mtd/devices/mchp23k256.c
new file mode 100644
index 000000000000..e237db9f1bdb
--- /dev/null
+++ b/drivers/mtd/devices/mchp23k256.c
@@ -0,0 +1,182 @@
+/*
+ * 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>
+
+struct mchp23k256_flash {
+        struct spi_device       *spi;
+        struct mutex            lock;
+        struct mtd_info         mtd;
+};
+
+#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 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[3];
+
+        spi_message_init(&message);
+
+        command[0] = MCHP23K256_CMD_WRITE;
+        command[1] = to >> 8;
+        command[2] = to;
+
+        transfer[0].tx_buf = command;
+        transfer[0].len = sizeof(command);
+        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[3];
+
+        spi_message_init(&message);
+
+        memset(&transfer, 0, sizeof(transfer));
+        command[0] = MCHP23K256_CMD_READ;
+        command[1] = from >> 8;
+        command[2] = from;
+
+        transfer[0].tx_buf = command;
+        transfer[0].len = sizeof(command);
+        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 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->mtd.dev.parent   = &spi->dev;
+        flash->mtd.type         = MTD_RAM;
+        flash->mtd.flags        = MTD_CAP_RAM;
+        flash->mtd.writesize    = 1;
+        flash->mtd.size         = SZ_32K;
+        flash->mtd._read        = mchp23k256_read;
+        flash->mtd._write       = mchp23k256_write;
+
+        err = mtd_device_parse_register(&flash->mtd, NULL, NULL,
+                                        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 struct spi_driver mchp23k256_driver = {
+        .driver = {
+                .name   = "mchp23k256",
+        },
+        .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");