i2c: muxes: rename first set of drivers to a standard pattern

Apply a naming pattern like in the rest of the subsystem to a first set
of mux drivers. Those drivers are the low-hanging fruit; we want to pick
them to motivate upcoming drivers to follow the new pattern. The missing
GPIO driver will be converted in a later patch.

Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
Acked-by: Guenter Roeck <guenter.roeck@ericsson.com> (pca9541)
Acked-by: Jean Delvare <khali@linux-fr.org>

1 files changed, 401 insertions, 0 deletions

diff --git a/drivers/i2c/muxes/i2c-mux-pca9541.c b/drivers/i2c/muxes/i2c-mux-pca9541.c
new file mode 100644
index 000000000000..8aacde1516ac
--- /dev/null
+++ b/drivers/i2c/muxes/i2c-mux-pca9541.c
@@ -0,0 +1,401 @@
+/*
+ * I2C multiplexer driver for PCA9541 bus master selector
+ *
+ * Copyright (c) 2010 Ericsson AB.
+ *
+ * Author: Guenter Roeck <guenter.roeck@ericsson.com>
+ *
+ * Derived from:
+ *  pca954x.c
+ *
+ *  Copyright (c) 2008-2009 Rodolfo Giometti <giometti@linux.it>
+ *  Copyright (c) 2008-2009 Eurotech S.p.A. <info@eurotech.it>
+ *
+ * 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/jiffies.h>
+#include <linux/delay.h>
+#include <linux/slab.h>
+#include <linux/device.h>
+#include <linux/i2c.h>
+#include <linux/i2c-mux.h>
+
+#include <linux/i2c/pca954x.h>
+
+/*
+ * The PCA9541 is a bus master selector. It supports two I2C masters connected
+ * to a single slave bus.
+ *
+ * Before each bus transaction, a master has to acquire bus ownership. After the
+ * transaction is complete, bus ownership has to be released. This fits well
+ * into the I2C multiplexer framework, which provides select and release
+ * functions for this purpose. For this reason, this driver is modeled as
+ * single-channel I2C bus multiplexer.
+ *
+ * This driver assumes that the two bus masters are controlled by two different
+ * hosts. If a single host controls both masters, platform code has to ensure
+ * that only one of the masters is instantiated at any given time.
+ */
+
+#define PCA9541_CONTROL		0x01
+#define PCA9541_ISTAT		0x02
+
+#define PCA9541_CTL_MYBUS	(1 << 0)
+#define PCA9541_CTL_NMYBUS	(1 << 1)
+#define PCA9541_CTL_BUSON	(1 << 2)
+#define PCA9541_CTL_NBUSON	(1 << 3)
+#define PCA9541_CTL_BUSINIT	(1 << 4)
+#define PCA9541_CTL_TESTON	(1 << 6)
+#define PCA9541_CTL_NTESTON	(1 << 7)
+
+#define PCA9541_ISTAT_INTIN	(1 << 0)
+#define PCA9541_ISTAT_BUSINIT	(1 << 1)
+#define PCA9541_ISTAT_BUSOK	(1 << 2)
+#define PCA9541_ISTAT_BUSLOST	(1 << 3)
+#define PCA9541_ISTAT_MYTEST	(1 << 6)
+#define PCA9541_ISTAT_NMYTEST	(1 << 7)
+
+#define BUSON		(PCA9541_CTL_BUSON | PCA9541_CTL_NBUSON)
+#define MYBUS		(PCA9541_CTL_MYBUS | PCA9541_CTL_NMYBUS)
+#define mybus(x)	(!((x) & MYBUS) || ((x) & MYBUS) == MYBUS)
+#define busoff(x)	(!((x) & BUSON) || ((x) & BUSON) == BUSON)
+
+/* arbitration timeouts, in jiffies */
+#define ARB_TIMEOUT	(HZ / 8)	/* 125 ms until forcing bus ownership */
+#define ARB2_TIMEOUT	(HZ / 4)	/* 250 ms until acquisition failure */
+
+/* arbitration retry delays, in us */
+#define SELECT_DELAY_SHORT	50
+#define SELECT_DELAY_LONG	1000
+
+struct pca9541 {
+	struct i2c_adapter *mux_adap;
+	unsigned long select_timeout;
+	unsigned long arb_timeout;
+};
+
+static const struct i2c_device_id pca9541_id[] = {
+	{"pca9541", 0},
+	{}
+};
+
+MODULE_DEVICE_TABLE(i2c, pca9541_id);
+
+/*
+ * Write to chip register. Don't use i2c_transfer()/i2c_smbus_xfer()
+ * as they will try to lock the adapter a second time.
+ */
+static int pca9541_reg_write(struct i2c_client *client, u8 command, u8 val)
+{
+	struct i2c_adapter *adap = client->adapter;
+	int ret;
+
+	if (adap->algo->master_xfer) {
+		struct i2c_msg msg;
+		char buf[2];
+
+		msg.addr = client->addr;
+		msg.flags = 0;
+		msg.len = 2;
+		buf[0] = command;
+		buf[1] = val;
+		msg.buf = buf;
+		ret = adap->algo->master_xfer(adap, &msg, 1);
+	} else {
+		union i2c_smbus_data data;
+
+		data.byte = val;
+		ret = adap->algo->smbus_xfer(adap, client->addr,
+					     client->flags,
+					     I2C_SMBUS_WRITE,
+					     command,
+					     I2C_SMBUS_BYTE_DATA, &data);
+	}
+
+	return ret;
+}
+
+/*
+ * Read from chip register. Don't use i2c_transfer()/i2c_smbus_xfer()
+ * as they will try to lock adapter a second time.
+ */
+static int pca9541_reg_read(struct i2c_client *client, u8 command)
+{
+	struct i2c_adapter *adap = client->adapter;
+	int ret;
+	u8 val;
+
+	if (adap->algo->master_xfer) {
+		struct i2c_msg msg[2] = {
+			{
+				.addr = client->addr,
+				.flags = 0,
+				.len = 1,
+				.buf = &command
+			},
+			{
+				.addr = client->addr,
+				.flags = I2C_M_RD,
+				.len = 1,
+				.buf = &val
+			}
+		};
+		ret = adap->algo->master_xfer(adap, msg, 2);
+		if (ret == 2)
+			ret = val;
+		else if (ret >= 0)
+			ret = -EIO;
+	} else {
+		union i2c_smbus_data data;
+
+		ret = adap->algo->smbus_xfer(adap, client->addr,
+					     client->flags,
+					     I2C_SMBUS_READ,
+					     command,
+					     I2C_SMBUS_BYTE_DATA, &data);
+		if (!ret)
+			ret = data.byte;
+	}
+	return ret;
+}
+
+/*
+ * Arbitration management functions
+ */
+
+/* Release bus. Also reset NTESTON and BUSINIT if it was set. */
+static void pca9541_release_bus(struct i2c_client *client)
+{
+	int reg;
+
+	reg = pca9541_reg_read(client, PCA9541_CONTROL);
+	if (reg >= 0 && !busoff(reg) && mybus(reg))
+		pca9541_reg_write(client, PCA9541_CONTROL,
+				  (reg & PCA9541_CTL_NBUSON) >> 1);
+}
+
+/*
+ * Arbitration is defined as a two-step process. A bus master can only activate
+ * the slave bus if it owns it; otherwise it has to request ownership first.
+ * This multi-step process ensures that access contention is resolved
+ * gracefully.
+ *
+ * Bus	Ownership	Other master	Action
+ * state		requested access
+ * ----------------------------------------------------
+ * off	-		yes		wait for arbitration timeout or
+ *					for other master to drop request
+ * off	no		no		take ownership
+ * off	yes		no		turn on bus
+ * on	yes		-		done
+ * on	no		-		wait for arbitration timeout or
+ *					for other master to release bus
+ *
+ * The main contention point occurs if the slave bus is off and both masters
+ * request ownership at the same time. In this case, one master will turn on
+ * the slave bus, believing that it owns it. The other master will request
+ * bus ownership. Result is that the bus is turned on, and master which did
+ * _not_ own the slave bus before ends up owning it.
+ */
+
+/* Control commands per PCA9541 datasheet */
+static const u8 pca9541_control[16] = {
+	4, 0, 1, 5, 4, 4, 5, 5, 0, 0, 1, 1, 0, 4, 5, 1
+};
+
+/*
+ * Channel arbitration
+ *
+ * Return values:
+ *  <0: error
+ *  0 : bus not acquired
+ *  1 : bus acquired
+ */
+static int pca9541_arbitrate(struct i2c_client *client)
+{
+	struct pca9541 *data = i2c_get_clientdata(client);
+	int reg;
+
+	reg = pca9541_reg_read(client, PCA9541_CONTROL);
+	if (reg < 0)
+		return reg;
+
+	if (busoff(reg)) {
+		int istat;
+		/*
+		 * Bus is off. Request ownership or turn it on unless
+		 * other master requested ownership.
+		 */
+		istat = pca9541_reg_read(client, PCA9541_ISTAT);
+		if (!(istat & PCA9541_ISTAT_NMYTEST)
+		    || time_is_before_eq_jiffies(data->arb_timeout)) {
+			/*
+			 * Other master did not request ownership,
+			 * or arbitration timeout expired. Take the bus.
+			 */
+			pca9541_reg_write(client,
+					  PCA9541_CONTROL,
+					  pca9541_control[reg & 0x0f]
+					  | PCA9541_CTL_NTESTON);
+			data->select_timeout = SELECT_DELAY_SHORT;
+		} else {
+			/*
+			 * Other master requested ownership.
+			 * Set extra long timeout to give it time to acquire it.
+			 */
+			data->select_timeout = SELECT_DELAY_LONG * 2;
+		}
+	} else if (mybus(reg)) {
+		/*
+		 * Bus is on, and we own it. We are done with acquisition.
+		 * Reset NTESTON and BUSINIT, then return success.
+		 */
+		if (reg & (PCA9541_CTL_NTESTON | PCA9541_CTL_BUSINIT))
+			pca9541_reg_write(client,
+					  PCA9541_CONTROL,
+					  reg & ~(PCA9541_CTL_NTESTON
+						  | PCA9541_CTL_BUSINIT));
+		return 1;
+	} else {
+		/*
+		 * Other master owns the bus.
+		 * If arbitration timeout has expired, force ownership.
+		 * Otherwise request it.
+		 */
+		data->select_timeout = SELECT_DELAY_LONG;
+		if (time_is_before_eq_jiffies(data->arb_timeout)) {
+			/* Time is up, take the bus and reset it. */
+			pca9541_reg_write(client,
+					  PCA9541_CONTROL,
+					  pca9541_control[reg & 0x0f]
+					  | PCA9541_CTL_BUSINIT
+					  | PCA9541_CTL_NTESTON);
+		} else {
+			/* Request bus ownership if needed */
+			if (!(reg & PCA9541_CTL_NTESTON))
+				pca9541_reg_write(client,
+						  PCA9541_CONTROL,
+						  reg | PCA9541_CTL_NTESTON);
+		}
+	}
+	return 0;
+}
+
+static int pca9541_select_chan(struct i2c_adapter *adap, void *client, u32 chan)
+{
+	struct pca9541 *data = i2c_get_clientdata(client);
+	int ret;
+	unsigned long timeout = jiffies + ARB2_TIMEOUT;
+		/* give up after this time */
+
+	data->arb_timeout = jiffies + ARB_TIMEOUT;
+		/* force bus ownership after this time */
+
+	do {
+		ret = pca9541_arbitrate(client);
+		if (ret)
+			return ret < 0 ? ret : 0;
+
+		if (data->select_timeout == SELECT_DELAY_SHORT)
+			udelay(data->select_timeout);
+		else
+			msleep(data->select_timeout / 1000);
+	} while (time_is_after_eq_jiffies(timeout));
+
+	return -ETIMEDOUT;
+}
+
+static int pca9541_release_chan(struct i2c_adapter *adap,
+				void *client, u32 chan)
+{
+	pca9541_release_bus(client);
+	return 0;
+}
+
+/*
+ * I2C init/probing/exit functions
+ */
+static int pca9541_probe(struct i2c_client *client,
+			 const struct i2c_device_id *id)
+{
+	struct i2c_adapter *adap = client->adapter;
+	struct pca954x_platform_data *pdata = client->dev.platform_data;
+	struct pca9541 *data;
+	int force;
+	int ret = -ENODEV;
+
+	if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_BYTE_DATA))
+		goto err;
+
+	data = kzalloc(sizeof(struct pca9541), GFP_KERNEL);
+	if (!data) {
+		ret = -ENOMEM;
+		goto err;
+	}
+
+	i2c_set_clientdata(client, data);
+
+	/*
+	 * I2C accesses are unprotected here.
+	 * We have to lock the adapter before releasing the bus.
+	 */
+	i2c_lock_adapter(adap);
+	pca9541_release_bus(client);
+	i2c_unlock_adapter(adap);
+
+	/* Create mux adapter */
+
+	force = 0;
+	if (pdata)
+		force = pdata->modes[0].adap_id;
+	data->mux_adap = i2c_add_mux_adapter(adap, &client->dev, client,
+					     force, 0,
+					     pca9541_select_chan,
+					     pca9541_release_chan);
+
+	if (data->mux_adap == NULL) {
+		dev_err(&client->dev, "failed to register master selector\n");
+		goto exit_free;
+	}
+
+	dev_info(&client->dev, "registered master selector for I2C %s\n",
+		 client->name);
+
+	return 0;
+
+exit_free:
+	kfree(data);
+err:
+	return ret;
+}
+
+static int pca9541_remove(struct i2c_client *client)
+{
+	struct pca9541 *data = i2c_get_clientdata(client);
+
+	i2c_del_mux_adapter(data->mux_adap);
+
+	kfree(data);
+	return 0;
+}
+
+static struct i2c_driver pca9541_driver = {
+	.driver = {
+		   .name = "pca9541",
+		   .owner = THIS_MODULE,
+		   },
+	.probe = pca9541_probe,
+	.remove = pca9541_remove,
+	.id_table = pca9541_id,
+};
+
+module_i2c_driver(pca9541_driver);
+
+MODULE_AUTHOR("Guenter Roeck <guenter.roeck@ericsson.com>");
+MODULE_DESCRIPTION("PCA9541 I2C master selector driver");
+MODULE_LICENSE("GPL v2");