[PATCH] max6875: new i2c device driver

This patch adds support for the MAX6875/MAX6874 chips.

Signed-off-by: Ben Gardner <bgardner@wabtec.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

4 files changed, 540 insertions, 0 deletions

diff --git a/Documentation/i2c/chips/max6875 b/Documentation/i2c/chips/max6875
new file mode 100644
index 00000000000..b4fb49b4181
--- /dev/null
+++ b/Documentation/i2c/chips/max6875
@@ -0,0 +1,54 @@
+Kernel driver max6875
+=====================
+
+Supported chips:
+  * Maxim max6874, max6875
+    Prefixes: 'max6875'
+    Addresses scanned: 0x50, 0x52
+    Datasheets:
+        http://pdfserv.maxim-ic.com/en/ds/MAX6874-MAX6875.pdf
+
+Author: Ben Gardner <bgardner@wabtec.com>
+
+
+Module Parameters
+-----------------
+
+* allow_write int
+  Set to non-zero to enable write permission:
+  *0: Read only
+   1: Read and write
+
+
+Description
+-----------
+
+The MAXIM max6875 is a EEPROM-programmable power-supply sequencer/supervisor.
+It provides timed outputs that can be used as a watchdog, if properly wired.
+It also provides 512 bytes of user EEPROM.
+
+At reset, the max6875 reads the configuration eeprom into its configuration
+registers.  The chip then begins to operate according to the values in the
+registers.
+
+See the datasheet for details on how to program the EEPROM.
+
+
+Sysfs entries
+-------------
+
+eeprom_user   - 512 bytes of user-defined EEPROM space. Only writable if
+                allow_write was set and register 0x43 is 0.
+
+eeprom_config - 70 bytes of config EEPROM. Note that changes will not get
+                loaded into register space until a power cycle or device reset.
+
+reg_config    - 70 bytes of register space. Any changes take affect immediately.
+
+
+General Remarks
+---------------
+
+A typical application will require that the EEPROMs be programmed once and
+never altered afterwards.
+
diff --git a/drivers/i2c/chips/Kconfig b/drivers/i2c/chips/Kconfig
index 2ce6907a07a..88437d04651 100644
--- a/drivers/i2c/chips/Kconfig
+++ b/drivers/i2c/chips/Kconfig
@@ -498,4 +498,16 @@ config SENSORS_M41T00
           This driver can also be built as a module.  If so, the module
           will be called m41t00.
 
+config SENSORS_MAX6875
+        tristate "MAXIM MAX6875 Power supply supervisor"
+        depends on I2C && EXPERIMENTAL
+        help
+          If you say yes here you get support for the MAX6875
+          EEPROM-Programmable, Hex/Quad, Power-Suppy Sequencers/Supervisors.
+
+          This provides a interface to program the EEPROM and reset the chip.
+
+          This driver can also be built as a module.  If so, the module
+          will be called max6875.
+
 endmenu
diff --git a/drivers/i2c/chips/Makefile b/drivers/i2c/chips/Makefile
index 5054ba5e470..8eed2381da6 100644
--- a/drivers/i2c/chips/Makefile
+++ b/drivers/i2c/chips/Makefile
@@ -32,6 +32,7 @@ obj-$(CONFIG_SENSORS_LM87)	+= lm87.o
 obj-$(CONFIG_SENSORS_LM90)      += lm90.o
 obj-$(CONFIG_SENSORS_LM92)      += lm92.o
 obj-$(CONFIG_SENSORS_MAX1619)   += max1619.o
+obj-$(CONFIG_SENSORS_MAX6875)   += max6875.o
 obj-$(CONFIG_SENSORS_M41T00)    += m41t00.o
 obj-$(CONFIG_SENSORS_PC87360)   += pc87360.o
 obj-$(CONFIG_SENSORS_PCF8574)   += pcf8574.o
diff --git a/drivers/i2c/chips/max6875.c b/drivers/i2c/chips/max6875.c
new file mode 100644
index 00000000000..fe6b150ec4c
--- /dev/null
+++ b/drivers/i2c/chips/max6875.c
@@ -0,0 +1,473 @@
+/*
+    max6875.c - driver for MAX6874/MAX6875
+
+    Copyright (C) 2005 Ben Gardner <bgardner@wabtec.com>
+
+    Based on i2c/chips/eeprom.c
+
+    The MAX6875 has two EEPROM sections: config and user.
+    At reset, the config EEPROM is read into the registers.
+
+    This driver make 3 binary files available in sysfs:
+      reg_config    - direct access to the registers
+      eeprom_config - acesses configuration eeprom space
+      eeprom_user   - free for application use
+
+    In our application, we put device serial & model numbers in user eeprom.
+
+    Notes:
+      1) The datasheet says that register 0x44 / EEPROM 0x8044 should NOT
+         be overwritten, so the driver explicitly prevents that.
+      2) It's a good idea to keep the config (0x45) locked in config EEPROM.
+         You can temporarily enable config writes by changing register 0x45.
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; version 2 of the License.
+*/
+
+#include <linux/config.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/sched.h>
+#include <linux/delay.h>
+#include <linux/i2c.h>
+#include <linux/i2c-sensor.h>
+
+/* Addresses to scan */
+static unsigned short normal_i2c[] = {0x50, 0x52, I2C_CLIENT_END};
+static unsigned int normal_isa[] = {I2C_CLIENT_ISA_END};
+
+/* Insmod parameters */
+SENSORS_INSMOD_1(max6875);
+
+/* this param will prevent 'accidental' writes to the eeprom */
+static int allow_write = 0;
+module_param(allow_write, int, 0);
+MODULE_PARM_DESC(allow_write,
+                 "Enable write access:\n"
+                 "*0: Read only\n"
+                 " 1: Read/Write access");
+
+/* The MAX6875 can only read/write 16 bytes at a time */
+#define SLICE_SIZE                      16
+#define SLICE_BITS                      4
+
+/* CONFIG EEPROM is at addresses 0x8000 - 0x8045, registers are at 0 - 0x45 */
+#define CONFIG_EEPROM_BASE              0x8000
+#define CONFIG_EEPROM_SIZE              0x0046
+#define CONFIG_EEPROM_SLICES            5
+
+/* USER EEPROM is at addresses 0x8100 - 0x82FF */
+#define USER_EEPROM_BASE                0x8100
+#define USER_EEPROM_SIZE                0x0200
+#define USER_EEPROM_SLICES              32
+
+/* MAX6875 commands */
+#define MAX6875_CMD_BLOCK_WRITE         0x83
+#define MAX6875_CMD_BLOCK_READ          0x84
+#define MAX6875_CMD_REBOOT              0x88
+
+enum max6875_area_type {
+        max6875_register_config=0,
+        max6875_eeprom_config,
+        max6875_eeprom_user,
+        max6857_max
+};
+
+struct eeprom_block {
+        enum max6875_area_type  type;
+        u8                      slices;
+        u32                     size;
+        u32                     valid;
+        u32                     base;
+        unsigned long           *updated;
+        u8                      *data;
+};
+
+/* Each client has this additional data */
+struct max6875_data {
+        struct i2c_client       client;
+        struct semaphore        update_lock;
+        struct eeprom_block     blocks[max6857_max];
+        /* the above structs point into the arrays below */
+        u8 data[USER_EEPROM_SIZE + (CONFIG_EEPROM_SIZE*2)];
+        unsigned long last_updated[USER_EEPROM_SLICES + (CONFIG_EEPROM_SLICES*2)];
+};
+
+static int max6875_attach_adapter(struct i2c_adapter *adapter);
+static int max6875_detect(struct i2c_adapter *adapter, int address, int kind);
+static int max6875_detach_client(struct i2c_client *client);
+
+/* This is the driver that will be inserted */
+static struct i2c_driver max6875_driver = {
+        .owner          = THIS_MODULE,
+        .name           = "max6875",
+        .flags          = I2C_DF_NOTIFY,
+        .attach_adapter = max6875_attach_adapter,
+        .detach_client  = max6875_detach_client,
+};
+
+static int max6875_update_slice(struct i2c_client *client,
+                                struct eeprom_block *blk,
+                                int slice)
+{
+        struct max6875_data *data = i2c_get_clientdata(client);
+        int i, j, addr, count;
+        u8 rdbuf[SLICE_SIZE];
+        int retval = 0;
+
+        if (slice >= blk->slices)
+                return -1;
+
+        down(&data->update_lock);
+
+        if (!(blk->valid & (1 << slice)) ||
+            (jiffies - blk->updated[slice] > 300 * HZ) ||
+            (jiffies < blk->updated[slice])) {
+                dev_dbg(&client->dev, "Starting eeprom update, slice %u, base %u\n",
+                        slice, blk->base);
+
+                addr = blk->base + (slice << SLICE_BITS);
+                count = blk->size - (slice << SLICE_BITS);
+                if (count > SLICE_SIZE) {
+                        count = SLICE_SIZE;
+                }
+
+                /* Preset the read address */
+                if (addr < 0x100) {
+                        /* select the register */
+                        if (i2c_smbus_write_byte(client, addr & 0xFF)) {
+                                dev_dbg(&client->dev, "max6875 register select has failed!\n");
+                                retval = -1;
+                                goto exit;
+                        }
+                } else {
+                        /* select the eeprom */
+                        if (i2c_smbus_write_byte_data(client, addr >> 8, addr & 0xFF)) {
+                                dev_dbg(&client->dev, "max6875 address set has failed!\n");
+                                retval = -1;
+                                goto exit;
+                        }
+                }
+
+                if (i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
+                        if (i2c_smbus_read_i2c_block_data(client, MAX6875_CMD_BLOCK_READ,
+                                                          rdbuf) != SLICE_SIZE)
+                        {
+                                retval = -1;
+                                goto exit;
+                        }
+
+                        memcpy(&blk->data[slice << SLICE_BITS], rdbuf, count);
+                } else {
+                        for (i = 0; i < count; i++) {
+                                j = i2c_smbus_read_byte(client);
+                                if (j < 0)
+                                {
+                                        retval = -1;
+                                        goto exit;
+                                }
+                                blk->data[(slice << SLICE_BITS) + i] = (u8) j;
+                        }
+                }
+                blk->updated[slice] = jiffies;
+                blk->valid |= (1 << slice);
+        }
+        exit:
+        up(&data->update_lock);
+        return retval;
+}
+
+static ssize_t max6875_read(struct kobject *kobj, char *buf, loff_t off, size_t count,
+                            enum max6875_area_type area_type)
+{
+        struct i2c_client *client = to_i2c_client(container_of(kobj, struct device, kobj));
+        struct max6875_data *data = i2c_get_clientdata(client);
+        struct eeprom_block *blk;
+        int slice;
+
+        blk = &data->blocks[area_type];
+
+        if (off > blk->size)
+                return 0;
+        if (off + count > blk->size)
+                count = blk->size - off;
+
+        /* Only refresh slices which contain requested bytes */
+        for (slice = (off >> SLICE_BITS); slice <= ((off + count - 1) >> SLICE_BITS); slice++)
+                max6875_update_slice(client, blk, slice);
+
+        memcpy(buf, &blk->data[off], count);
+
+        return count;
+}
+
+static ssize_t max6875_user_read(struct kobject *kobj, char *buf, loff_t off, size_t count)
+{
+        return max6875_read(kobj, buf, off, count, max6875_eeprom_user);
+}
+
+static ssize_t max6875_config_read(struct kobject *kobj, char *buf, loff_t off, size_t count)
+{
+        return max6875_read(kobj, buf, off, count, max6875_eeprom_config);
+}
+
+static ssize_t max6875_cfgreg_read(struct kobject *kobj, char *buf, loff_t off, size_t count)
+{
+        return max6875_read(kobj, buf, off, count, max6875_register_config);
+}
+
+
+static ssize_t max6875_write(struct kobject *kobj, char *buf, loff_t off, size_t count,
+                             enum max6875_area_type area_type)
+{
+        struct i2c_client *client = to_i2c_client(container_of(kobj, struct device, kobj));
+        struct max6875_data *data = i2c_get_clientdata(client);
+        struct eeprom_block *blk;
+        int slice, addr, retval;
+        ssize_t sent = 0;
+
+        blk = &data->blocks[area_type];
+
+        if (off > blk->size)
+                return 0;
+        if ((off + count) > blk->size)
+                count = blk->size - off;
+
+        if (down_interruptible(&data->update_lock))
+                return -EAGAIN;
+
+        /* writing to a register is done with i2c_smbus_write_byte_data() */
+        if (blk->type == max6875_register_config) {
+                for (sent = 0; sent < count; sent++) {
+                        addr = off + sent;
+                        if (addr == 0x44)
+                                continue;
+
+                        retval = i2c_smbus_write_byte_data(client, addr, buf[sent]);
+                }
+        } else {
+                int cmd, val;
+
+                /* We are writing to EEPROM */
+                for (sent = 0; sent < count; sent++) {
+                        addr = blk->base + off + sent;
+                        cmd = addr >> 8;
+                        val = (addr & 0xff) | (buf[sent] << 8); // reversed
+
+                        if (addr == 0x8044)
+                                continue;
+
+                        retval = i2c_smbus_write_word_data(client, cmd, val);
+
+                        if (retval) {
+                                goto error_exit;
+                        }
+
+                        /* A write takes up to 11 ms */
+                        msleep(11);
+                }
+        }
+
+        /* Invalidate the scratch buffer */
+        for (slice = (off >> SLICE_BITS); slice <= ((off + count - 1) >> SLICE_BITS); slice++)
+                blk->valid &= ~(1 << slice);
+
+        error_exit:
+        up(&data->update_lock);
+
+        return sent;
+}
+
+static ssize_t max6875_user_write(struct kobject *kobj, char *buf, loff_t off, size_t count)
+{
+        return max6875_write(kobj, buf, off, count, max6875_eeprom_user);
+}
+
+static ssize_t max6875_config_write(struct kobject *kobj, char *buf, loff_t off, size_t count)
+{
+        return max6875_write(kobj, buf, off, count, max6875_eeprom_config);
+}
+
+static ssize_t max6875_cfgreg_write(struct kobject *kobj, char *buf, loff_t off, size_t count)
+{
+        return max6875_write(kobj, buf, off, count, max6875_register_config);
+}
+
+static struct bin_attribute user_eeprom_attr = {
+        .attr = {
+                .name = "eeprom_user",
+                .mode = S_IRUGO | S_IWUSR | S_IWGRP,
+                .owner = THIS_MODULE,
+        },
+        .size  = USER_EEPROM_SIZE,
+        .read  = max6875_user_read,
+        .write = max6875_user_write,
+};
+
+static struct bin_attribute config_eeprom_attr = {
+        .attr = {
+                .name = "eeprom_config",
+                .mode = S_IRUGO | S_IWUSR,
+                .owner = THIS_MODULE,
+        },
+        .size  = CONFIG_EEPROM_SIZE,
+        .read  = max6875_config_read,
+        .write = max6875_config_write,
+};
+
+static struct bin_attribute config_register_attr = {
+        .attr = {
+                .name = "reg_config",
+                .mode = S_IRUGO | S_IWUSR,
+                .owner = THIS_MODULE,
+        },
+        .size  = CONFIG_EEPROM_SIZE,
+        .read  = max6875_cfgreg_read,
+        .write = max6875_cfgreg_write,
+};
+
+static int max6875_attach_adapter(struct i2c_adapter *adapter)
+{
+        return i2c_detect(adapter, &addr_data, max6875_detect);
+}
+
+/* This function is called by i2c_detect */
+static int max6875_detect(struct i2c_adapter *adapter, int address, int kind)
+{
+        struct i2c_client *new_client;
+        struct max6875_data *data;
+        int err = 0;
+
+        /* There are three ways we can read the EEPROM data:
+           (1) I2C block reads (faster, but unsupported by most adapters)
+           (2) Consecutive byte reads (100% overhead)
+           (3) Regular byte data reads (200% overhead)
+           The third method is not implemented by this driver because all
+           known adapters support at least the second. */
+        if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_BYTE_DATA |
+                                     I2C_FUNC_SMBUS_BYTE |
+                                     I2C_FUNC_SMBUS_WRITE_BYTE_DATA))
+                goto exit;
+
+        /* OK. For now, we presume we have a valid client. We now create the
+           client structure, even though we cannot fill it completely yet.
+           But it allows us to access eeprom_{read,write}_value. */
+        if (!(data = kmalloc(sizeof(struct max6875_data), GFP_KERNEL))) {
+                err = -ENOMEM;
+                goto exit;
+        }
+        memset(data, 0, sizeof(struct max6875_data));
+
+        new_client = &data->client;
+        i2c_set_clientdata(new_client, data);
+        new_client->addr = address;
+        new_client->adapter = adapter;
+        new_client->driver = &max6875_driver;
+        new_client->flags = 0;
+
+        /* Setup the user section */
+        data->blocks[max6875_eeprom_user].type    = max6875_eeprom_user;
+        data->blocks[max6875_eeprom_user].slices  = USER_EEPROM_SLICES;
+        data->blocks[max6875_eeprom_user].size    = USER_EEPROM_SIZE;
+        data->blocks[max6875_eeprom_user].base    = USER_EEPROM_BASE;
+        data->blocks[max6875_eeprom_user].data    = data->data;
+        data->blocks[max6875_eeprom_user].updated = data->last_updated;
+
+        /* Setup the config section */
+        data->blocks[max6875_eeprom_config].type    = max6875_eeprom_config;
+        data->blocks[max6875_eeprom_config].slices  = CONFIG_EEPROM_SLICES;
+        data->blocks[max6875_eeprom_config].size    = CONFIG_EEPROM_SIZE;
+        data->blocks[max6875_eeprom_config].base    = CONFIG_EEPROM_BASE;
+        data->blocks[max6875_eeprom_config].data    = &data->data[USER_EEPROM_SIZE];
+        data->blocks[max6875_eeprom_config].updated = &data->last_updated[USER_EEPROM_SLICES];
+
+        /* Setup the register section */
+        data->blocks[max6875_register_config].type    = max6875_register_config;
+        data->blocks[max6875_register_config].slices  = CONFIG_EEPROM_SLICES;
+        data->blocks[max6875_register_config].size    = CONFIG_EEPROM_SIZE;
+        data->blocks[max6875_register_config].base    = 0;
+        data->blocks[max6875_register_config].data    = &data->data[USER_EEPROM_SIZE+CONFIG_EEPROM_SIZE];
+        data->blocks[max6875_register_config].updated = &data->last_updated[USER_EEPROM_SLICES+CONFIG_EEPROM_SLICES];
+
+        /* Init the data */
+        memset(data->data, 0xff, sizeof(data->data));
+
+        /* Fill in the remaining client fields */
+        strlcpy(new_client->name, "max6875", I2C_NAME_SIZE);
+        init_MUTEX(&data->update_lock);
+
+        /* Verify that the chip is really what we think it is */
+        if ((max6875_update_slice(new_client, &data->blocks[max6875_eeprom_config], 4) < 0) ||
+            (max6875_update_slice(new_client, &data->blocks[max6875_register_config], 4) < 0))
+                goto exit_kfree;
+
+        /* 0x41,0x42 must be zero and 0x40 must match in eeprom and registers */
+        if ((data->blocks[max6875_eeprom_config].data[0x41] != 0) ||
+            (data->blocks[max6875_eeprom_config].data[0x42] != 0) ||
+            (data->blocks[max6875_register_config].data[0x41] != 0) ||
+            (data->blocks[max6875_register_config].data[0x42] != 0) ||
+            (data->blocks[max6875_eeprom_config].data[0x40] !=
+             data->blocks[max6875_register_config].data[0x40]))
+                goto exit_kfree;
+
+        /* Tell the I2C layer a new client has arrived */
+        if ((err = i2c_attach_client(new_client)))
+                goto exit_kfree;
+
+        /* create the sysfs eeprom files with the correct permissions */
+        if (allow_write == 0) {
+                user_eeprom_attr.attr.mode &= ~S_IWUGO;
+                user_eeprom_attr.write = NULL;
+                config_eeprom_attr.attr.mode &= ~S_IWUGO;
+                config_eeprom_attr.write = NULL;
+                config_register_attr.attr.mode &= ~S_IWUGO;
+                config_register_attr.write = NULL;
+        }
+        sysfs_create_bin_file(&new_client->dev.kobj, &user_eeprom_attr);
+        sysfs_create_bin_file(&new_client->dev.kobj, &config_eeprom_attr);
+        sysfs_create_bin_file(&new_client->dev.kobj, &config_register_attr);
+
+        return 0;
+
+exit_kfree:
+        kfree(data);
+exit:
+        return err;
+}
+
+static int max6875_detach_client(struct i2c_client *client)
+{
+        int err;
+
+        err = i2c_detach_client(client);
+        if (err) {
+                dev_err(&client->dev, "Client deregistration failed, client not detached.\n");
+                return err;
+        }
+
+        kfree(i2c_get_clientdata(client));
+
+        return 0;
+}
+
+static int __init max6875_init(void)
+{
+        return i2c_add_driver(&max6875_driver);
+}
+
+static void __exit max6875_exit(void)
+{
+        i2c_del_driver(&max6875_driver);
+}
+
+
+MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>");
+MODULE_DESCRIPTION("MAX6875 driver");
+MODULE_LICENSE("GPL");
+
+module_init(max6875_init);
+module_exit(max6875_exit);