i2c: I2C bus multiplexer driver pca954x
authorMichael Lawnick <ml.lawnick@gmx.de>
Wed, 11 Aug 2010 16:21:03 +0000 (18:21 +0200)
committerJean Delvare <khali@linux-fr.org>
Wed, 11 Aug 2010 16:21:03 +0000 (18:21 +0200)
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>
drivers/i2c/Kconfig
drivers/i2c/Makefile
drivers/i2c/muxes/Kconfig [new file with mode: 0644]
drivers/i2c/muxes/Makefile [new file with mode: 0644]
drivers/i2c/muxes/pca954x.c [new file with mode: 0644]
include/linux/i2c/pca954x.h [new file with mode: 0644]

index efb48ad..30f06e9 100644 (file)
@@ -58,6 +58,8 @@ config I2C_MUX
          This support is also available as a module.  If so, the module
          will be called i2c-mux.
 
+source drivers/i2c/muxes/Kconfig
+
 config I2C_HELPER_AUTO
        bool "Autoselect pertinent helper modules"
        default y
index f363258..c00fd66 100644 (file)
@@ -7,7 +7,7 @@ obj-$(CONFIG_I2C)               += i2c-core.o
 obj-$(CONFIG_I2C_SMBUS)                += i2c-smbus.o
 obj-$(CONFIG_I2C_CHARDEV)      += i2c-dev.o
 obj-$(CONFIG_I2C_MUX)          += i2c-mux.o
-obj-y                          += algos/ busses/
+obj-y                          += algos/ busses/ muxes/
 
 ifeq ($(CONFIG_I2C_DEBUG_CORE),y)
 EXTRA_CFLAGS += -DDEBUG
diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
new file mode 100644 (file)
index 0000000..4c9a99c
--- /dev/null
@@ -0,0 +1,18 @@
+#
+# Multiplexer I2C chip drivers configuration
+#
+
+menu "Multiplexer I2C Chip support"
+       depends on I2C_MUX
+
+config I2C_MUX_PCA954x
+       tristate "Philips PCA954x I2C Mux/switches"
+       depends on EXPERIMENTAL
+       help
+         If you say yes here you get support for the Philips PCA954x
+         I2C mux/switch devices.
+
+         This driver can also be built as a module.  If so, the module
+         will be called pca954x.
+
+endmenu
diff --git a/drivers/i2c/muxes/Makefile b/drivers/i2c/muxes/Makefile
new file mode 100644 (file)
index 0000000..bd83b52
--- /dev/null
@@ -0,0 +1,8 @@
+#
+# Makefile for multiplexer I2C chip drivers.
+
+obj-$(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 (file)
index 0000000..6f9accf
--- /dev/null
@@ -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");
diff --git a/include/linux/i2c/pca954x.h b/include/linux/i2c/pca954x.h
new file mode 100644 (file)
index 0000000..28f1f8d
--- /dev/null
@@ -0,0 +1,47 @@
+/*
+ *
+ * pca954x.h - I2C multiplexer/switch support
+ *
+ * Copyright (c) 2008-2009 Rodolfo Giometti <giometti@linux.it>
+ * Copyright (c) 2008-2009 Eurotech S.p.A. <info@eurotech.it>
+ * Michael Lawnick <michael.lawnick.ext@nsn.com>
+ *
+ * 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; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+
+#ifndef _LINUX_I2C_PCA954X_H
+#define _LINUX_I2C_PCA954X_H
+
+/* Platform data for the PCA954x I2C multiplexers */
+
+/* Per channel initialisation data:
+ * @adap_id: bus number for the adapter. 0 = don't care
+ * @deselect_on_exit: set this entry to 1, if your H/W needs deselection
+ *                    of this channel after transaction.
+ *
+ */
+struct pca954x_platform_mode {
+       int             adap_id;
+       unsigned int    deselect_on_exit:1;
+};
+
+/* Per mux/switch data, used with i2c_register_board_info */
+struct pca954x_platform_data {
+       struct pca954x_platform_mode *modes;
+       int num_modes;
+};
+
+#endif /* _LINUX_I2C_PCA954X_H */