i2c: I2C bus multiplexer driver pca954x

I2C driver for PCA954x I2C multiplexer series.

Signed-off-by: Michael Lawnick <ml.lawnick@gmx.de>
Acked-by: Rodolfo Giometti <giometti@linux.it>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

3 files changed, 327 insertions, 0 deletions

diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
new file mode 100644
index 000000000000..4c9a99c4fcb0
--- /dev/null
+++ b/drivers/i2c/muxes/Kconfig
@@ -0,0 +1,18 @@
+#
+# Multiplexer I2C chip drivers configuration
+#
+
+menu "Multiplexer I2C Chip support"
+        depends on I2C_MUX
+
+config I2C_MUX_PCA954x
+        tristate "Philips PCA954x I2C Mux/switches"
+        depends on EXPERIMENTAL
+        help
+          If you say yes here you get support for the Philips PCA954x
+          I2C mux/switch devices.
+
+          This driver can also be built as a module.  If so, the module
+          will be called pca954x.
+
+endmenu
diff --git a/drivers/i2c/muxes/Makefile b/drivers/i2c/muxes/Makefile
new file mode 100644
index 000000000000..bd83b5274815
--- /dev/null
+++ b/drivers/i2c/muxes/Makefile
@@ -0,0 +1,8 @@
+#
+# Makefile for multiplexer I2C chip drivers.
+
+obj-$(CONFIG_I2C_MUX_PCA954x)   += pca954x.o
+
+ifeq ($(CONFIG_I2C_DEBUG_BUS),y)
+EXTRA_CFLAGS += -DDEBUG
+endif
diff --git a/drivers/i2c/muxes/pca954x.c b/drivers/i2c/muxes/pca954x.c
new file mode 100644
index 000000000000..6f9accf3189d
--- /dev/null
+++ b/drivers/i2c/muxes/pca954x.c
@@ -0,0 +1,301 @@
+/*
+ * I2C multiplexer
+ *
+ * Copyright (c) 2008-2009 Rodolfo Giometti <giometti@linux.it>
+ * Copyright (c) 2008-2009 Eurotech S.p.A. <info@eurotech.it>
+ *
+ * This module supports the PCA954x series of I2C multiplexer/switch chips
+ * made by Philips Semiconductors.
+ * This includes the:
+ *       PCA9540, PCA9542, PCA9543, PCA9544, PCA9545, PCA9546, PCA9547
+ *       and PCA9548.
+ *
+ * These chips are all controlled via the I2C bus itself, and all have a
+ * single 8-bit register. The upstream "parent" bus fans out to two,
+ * four, or eight downstream busses or channels; which of these
+ * are selected is determined by the chip type and register contents. A
+ * mux can select only one sub-bus at a time; a switch can select any
+ * combination simultaneously.
+ *
+ * Based on:
+ *      pca954x.c from Kumar Gala <galak@kernel.crashing.org>
+ * Copyright (C) 2006
+ *
+ * Based on:
+ *      pca954x.c from Ken Harrenstien
+ * Copyright (C) 2004 Google, Inc. (Ken Harrenstien)
+ *
+ * Based on:
+ *      i2c-virtual_cb.c from Brian Kuschak <bkuschak@yahoo.com>
+ * and
+ *      pca9540.c from Jean Delvare <khali@linux-fr.org>.
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/device.h>
+#include <linux/i2c.h>
+#include <linux/i2c-mux.h>
+
+#include <linux/i2c/pca954x.h>
+
+#define PCA954X_MAX_NCHANS 8
+
+enum pca_type {
+        pca_9540,
+        pca_9542,
+        pca_9543,
+        pca_9544,
+        pca_9545,
+        pca_9546,
+        pca_9547,
+        pca_9548,
+};
+
+struct pca954x {
+        enum pca_type type;
+        struct i2c_adapter *virt_adaps[PCA954X_MAX_NCHANS];
+
+        u8 last_chan;           /* last register value */
+};
+
+struct chip_desc {
+        u8 nchans;
+        u8 enable;      /* used for muxes only */
+        enum muxtype {
+                pca954x_ismux = 0,
+                pca954x_isswi
+        } muxtype;
+};
+
+/* Provide specs for the PCA954x types we know about */
+static const struct chip_desc chips[] = {
+        [pca_9540] = {
+                .nchans = 2,
+                .enable = 0x4,
+                .muxtype = pca954x_ismux,
+        },
+        [pca_9543] = {
+                .nchans = 2,
+                .muxtype = pca954x_isswi,
+        },
+        [pca_9544] = {
+                .nchans = 4,
+                .enable = 0x4,
+                .muxtype = pca954x_ismux,
+        },
+        [pca_9545] = {
+                .nchans = 4,
+                .muxtype = pca954x_isswi,
+        },
+        [pca_9547] = {
+                .nchans = 8,
+                .enable = 0x8,
+                .muxtype = pca954x_ismux,
+        },
+        [pca_9548] = {
+                .nchans = 8,
+                .muxtype = pca954x_isswi,
+        },
+};
+
+static const struct i2c_device_id pca954x_id[] = {
+        { "pca9540", pca_9540 },
+        { "pca9542", pca_9540 },
+        { "pca9543", pca_9543 },
+        { "pca9544", pca_9544 },
+        { "pca9545", pca_9545 },
+        { "pca9546", pca_9545 },
+        { "pca9547", pca_9547 },
+        { "pca9548", pca_9548 },
+        { }
+};
+MODULE_DEVICE_TABLE(i2c, pca954x_id);
+
+/* Write to mux register. Don't use i2c_transfer()/i2c_smbus_xfer()
+   for this as they will try to lock adapter a second time */
+static int pca954x_reg_write(struct i2c_adapter *adap,
+                             struct i2c_client *client, u8 val)
+{
+        int ret = -ENODEV;
+
+        if (adap->algo->master_xfer) {
+                struct i2c_msg msg;
+                char buf[1];
+
+                msg.addr = client->addr;
+                msg.flags = 0;
+                msg.len = 1;
+                buf[0] = val;
+                msg.buf = buf;
+                ret = adap->algo->master_xfer(adap, &msg, 1);
+        } else {
+                union i2c_smbus_data data;
+                ret = adap->algo->smbus_xfer(adap, client->addr,
+                                             client->flags,
+                                             I2C_SMBUS_WRITE,
+                                             val, I2C_SMBUS_BYTE, &data);
+        }
+
+        return ret;
+}
+
+static int pca954x_select_chan(struct i2c_adapter *adap,
+                               void *client, u32 chan)
+{
+        struct pca954x *data = i2c_get_clientdata(client);
+        const struct chip_desc *chip = &chips[data->type];
+        u8 regval;
+        int ret = 0;
+
+        /* we make switches look like muxes, not sure how to be smarter */
+        if (chip->muxtype == pca954x_ismux)
+                regval = chan | chip->enable;
+        else
+                regval = 1 << chan;
+
+        /* Only select the channel if its different from the last channel */
+        if (data->last_chan != regval) {
+                ret = pca954x_reg_write(adap, client, regval);
+                data->last_chan = regval;
+        }
+
+        return ret;
+}
+
+static int pca954x_deselect_mux(struct i2c_adapter *adap,
+                                void *client, u32 chan)
+{
+        struct pca954x *data = i2c_get_clientdata(client);
+
+        /* Deselect active channel */
+        data->last_chan = 0;
+        return pca954x_reg_write(adap, client, data->last_chan);
+}
+
+/*
+ * I2C init/probing/exit functions
+ */
+static int __devinit pca954x_probe(struct i2c_client *client,
+                                   const struct i2c_device_id *id)
+{
+        struct i2c_adapter *adap = to_i2c_adapter(client->dev.parent);
+        struct pca954x_platform_data *pdata = client->dev.platform_data;
+        int num, force;
+        struct pca954x *data;
+        int ret = -ENODEV;
+
+        if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_BYTE))
+                goto err;
+
+        data = kzalloc(sizeof(struct pca954x), GFP_KERNEL);
+        if (!data) {
+                ret = -ENOMEM;
+                goto err;
+        }
+
+        i2c_set_clientdata(client, data);
+
+        /* Read the mux register at addr to verify
+         * that the mux is in fact present.
+         */
+        if (i2c_smbus_read_byte(client) < 0) {
+                dev_warn(&client->dev, "probe failed\n");
+                goto exit_free;
+        }
+
+        data->type = id->driver_data;
+        data->last_chan = 0;               /* force the first selection */
+
+        /* Now create an adapter for each channel */
+        for (num = 0; num < chips[data->type].nchans; num++) {
+                force = 0;                        /* dynamic adap number */
+                if (pdata) {
+                        if (num < pdata->num_modes)
+                                /* force static number */
+                                force = pdata->modes[num].adap_id;
+                        else
+                                /* discard unconfigured channels */
+                                break;
+                }
+
+                data->virt_adaps[num] =
+                        i2c_add_mux_adapter(adap, client,
+                                force, num, pca954x_select_chan,
+                                (pdata && pdata->modes[num].deselect_on_exit)
+                                        ? pca954x_deselect_mux : NULL);
+
+                if (data->virt_adaps[num] == NULL) {
+                        ret = -ENODEV;
+                        dev_err(&client->dev,
+                                "failed to register multiplexed adapter"
+                                " %d as bus %d\n", num, force);
+                        goto virt_reg_failed;
+                }
+        }
+
+        dev_info(&client->dev,
+                 "registered %d multiplexed busses for I2C %s %s\n",
+                 num, chips[data->type].muxtype == pca954x_ismux
+                                ? "mux" : "switch", client->name);
+
+        return 0;
+
+virt_reg_failed:
+        for (num--; num >= 0; num--)
+                i2c_del_mux_adapter(data->virt_adaps[num]);
+exit_free:
+        kfree(data);
+err:
+        return ret;
+}
+
+static int __devexit pca954x_remove(struct i2c_client *client)
+{
+        struct pca954x *data = i2c_get_clientdata(client);
+        const struct chip_desc *chip = &chips[data->type];
+        int i, err;
+
+        for (i = 0; i < chip->nchans; ++i)
+                if (data->virt_adaps[i]) {
+                        err = i2c_del_mux_adapter(data->virt_adaps[i]);
+                        if (err)
+                                return err;
+                        data->virt_adaps[i] = NULL;
+                }
+
+        kfree(data);
+        return 0;
+}
+
+static struct i2c_driver pca954x_driver = {
+        .driver         = {
+                .name   = "pca954x",
+                .owner  = THIS_MODULE,
+        },
+        .probe          = pca954x_probe,
+        .remove         = __devexit_p(pca954x_remove),
+        .id_table       = pca954x_id,
+};
+
+static int __init pca954x_init(void)
+{
+        return i2c_add_driver(&pca954x_driver);
+}
+
+static void __exit pca954x_exit(void)
+{
+        i2c_del_driver(&pca954x_driver);
+}
+
+module_init(pca954x_init);
+module_exit(pca954x_exit);
+
+MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
+MODULE_DESCRIPTION("PCA954x I2C mux/switch driver");
+MODULE_LICENSE("GPL v2");