Adding upstream version 6.1.76.upstream/6.1.76upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 349 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 000000000..ea83de78f
--- /dev/null
+++ b/drivers/i2c/muxes/i2c-mux-pca9541.c
@@ -0,0 +1,349 @@
+/*
+ * I2C multiplexer driver for PCA9541 bus master selector
+ *
+ * Copyright (c) 2010 Ericsson AB.
+ *
+ * Author: Guenter Roeck <linux@roeck-us.net>
+ *
+ * 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/bitops.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/i2c.h>
+#include <linux/i2c-mux.h>
+#include <linux/jiffies.h>
+#include <linux/module.h>
+#include <linux/slab.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	BIT(0)
+#define PCA9541_CTL_NMYBUS	BIT(1)
+#define PCA9541_CTL_BUSON	BIT(2)
+#define PCA9541_CTL_NBUSON	BIT(3)
+#define PCA9541_CTL_BUSINIT	BIT(4)
+#define PCA9541_CTL_TESTON	BIT(6)
+#define PCA9541_CTL_NTESTON	BIT(7)
+
+#define PCA9541_ISTAT_INTIN	BIT(0)
+#define PCA9541_ISTAT_BUSINIT	BIT(1)
+#define PCA9541_ISTAT_BUSOK	BIT(2)
+#define PCA9541_ISTAT_BUSLOST	BIT(3)
+#define PCA9541_ISTAT_MYTEST	BIT(6)
+#define PCA9541_ISTAT_NMYTEST	BIT(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_client *client;
+	unsigned long select_timeout;
+	unsigned long arb_timeout;
+};
+
+static const struct i2c_device_id pca9541_id[] = {
+	{"pca9541", 0},
+	{}
+};
+
+MODULE_DEVICE_TABLE(i2c, pca9541_id);
+
+#ifdef CONFIG_OF
+static const struct of_device_id pca9541_of_match[] = {
+	{ .compatible = "nxp,pca9541" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, pca9541_of_match);
+#endif
+
+/*
+ * 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;
+	union i2c_smbus_data data = { .byte = val };
+
+	return __i2c_smbus_xfer(adap, client->addr, client->flags,
+				I2C_SMBUS_WRITE, command,
+				I2C_SMBUS_BYTE_DATA, &data);
+}
+
+/*
+ * 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;
+	union i2c_smbus_data data;
+	int ret;
+
+	ret = __i2c_smbus_xfer(adap, client->addr, client->flags,
+			       I2C_SMBUS_READ, command,
+			       I2C_SMBUS_BYTE_DATA, &data);
+
+	return ret ?: data.byte;
+}
+
+/*
+ * 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 i2c_mux_core *muxc = i2c_get_clientdata(client);
+	struct pca9541 *data = i2c_mux_priv(muxc);
+	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_mux_core *muxc, u32 chan)
+{
+	struct pca9541 *data = i2c_mux_priv(muxc);
+	struct i2c_client *client = data->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_mux_core *muxc, u32 chan)
+{
+	struct pca9541 *data = i2c_mux_priv(muxc);
+	struct i2c_client *client = data->client;
+
+	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 i2c_mux_core *muxc;
+	struct pca9541 *data;
+	int ret;
+
+	if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_BYTE_DATA))
+		return -ENODEV;
+
+	/*
+	 * I2C accesses are unprotected here.
+	 * We have to lock the I2C segment before releasing the bus.
+	 */
+	i2c_lock_bus(adap, I2C_LOCK_SEGMENT);
+	pca9541_release_bus(client);
+	i2c_unlock_bus(adap, I2C_LOCK_SEGMENT);
+
+	/* Create mux adapter */
+
+	muxc = i2c_mux_alloc(adap, &client->dev, 1, sizeof(*data),
+			     I2C_MUX_ARBITRATOR,
+			     pca9541_select_chan, pca9541_release_chan);
+	if (!muxc)
+		return -ENOMEM;
+
+	data = i2c_mux_priv(muxc);
+	data->client = client;
+
+	i2c_set_clientdata(client, muxc);
+
+	ret = i2c_mux_add_adapter(muxc, 0, 0, 0);
+	if (ret)
+		return ret;
+
+	dev_info(&client->dev, "registered master selector for I2C %s\n",
+		 client->name);
+
+	return 0;
+}
+
+static void pca9541_remove(struct i2c_client *client)
+{
+	struct i2c_mux_core *muxc = i2c_get_clientdata(client);
+
+	i2c_mux_del_adapters(muxc);
+}
+
+static struct i2c_driver pca9541_driver = {
+	.driver = {
+		   .name = "pca9541",
+		   .of_match_table = of_match_ptr(pca9541_of_match),
+		   },
+	.probe = pca9541_probe,
+	.remove = pca9541_remove,
+	.id_table = pca9541_id,
+};
+
+module_i2c_driver(pca9541_driver);
+
+MODULE_AUTHOR("Guenter Roeck <linux@roeck-us.net>");
+MODULE_DESCRIPTION("PCA9541 I2C master selector driver");
+MODULE_LICENSE("GPL v2");