[PATCH] i2c: New bus driver for the OpenCores I2C controller

The following patch adds support for the OpenCores I2C controller IP
core (See http://www.opencores.org/projects.cgi/web/i2c/overview).

Signed-off-by: Peter Korsgaard <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Jean Delvare <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/i2c/busses/i2c-ocores

···
+Kernel driver i2c-ocores
+
+Supported adapters:
+  * OpenCores.org I2C controller by Richard Herveille (see datasheet link)
+    Datasheet: http://www.opencores.org/projects.cgi/web/i2c/overview
+
+Author: Peter Korsgaard <[e-mail]>
+
+Description
+-----------
+
+i2c-ocores is an i2c bus driver for the OpenCores.org I2C controller
+IP core by Richard Herveille.
+
+Usage
+-----
+
+i2c-ocores uses the platform bus, so you need to provide a struct
+platform_device with the base address and interrupt number. The
+dev.platform_data of the device should also point to a struct
+ocores_i2c_platform_data (see linux/i2c-ocores.h) describing the
+distance between registers and the input clock speed.
+
+E.G. something like:
+
+static struct resource ocores_resources[] = {
+	[0] = {
+		.start	= MYI2C_BASEADDR,
+		.end	= MYI2C_BASEADDR + 8,
+		.flags	= IORESOURCE_MEM,
+	},
+	[1] = {
+		.start	= MYI2C_IRQ,
+		.end	= MYI2C_IRQ,
+		.flags	= IORESOURCE_IRQ,
+	},
+};
+
+static struct ocores_i2c_platform_data myi2c_data = {
+	.regstep	= 2,		/* two bytes between registers */
+	.clock_khz	= 50000,	/* input clock of 50MHz */
+};
+
+static struct platform_device myi2c = {
+	.name			= "ocores-i2c",
+	.dev = {
+		.platform_data	= &myi2c_data,
+	},
+	.num_resources		= ARRAY_SIZE(ocores_resources),
+	.resource		= ocores_resources,
+};

drivers/i2c/busses/Kconfig

···
 	  This driver can also be built as a module.  If so, the module
 	  will be called i2c-nforce2.
 
+config I2C_OCORES
+	tristate "OpenCores I2C Controller"
+	depends on I2C && EXPERIMENTAL
+	help
+	  If you say yes to this option, support will be included for the
+	  OpenCores I2C controller. For details see
+	  http://www.opencores.org/projects.cgi/web/i2c/overview
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called i2c-ocores.
+
 config I2C_PARPORT
 	tristate "Parallel port adapter"
 	depends on I2C && PARPORT

drivers/i2c/busses/Makefile

···
 obj-$(CONFIG_I2C_MPC)		+= i2c-mpc.o
 obj-$(CONFIG_I2C_MV64XXX)	+= i2c-mv64xxx.o
 obj-$(CONFIG_I2C_NFORCE2)	+= i2c-nforce2.o
+obj-$(CONFIG_I2C_OCORES)	+= i2c-ocores.o
 obj-$(CONFIG_I2C_PARPORT)	+= i2c-parport.o
 obj-$(CONFIG_I2C_PARPORT_LIGHT)	+= i2c-parport-light.o
 obj-$(CONFIG_I2C_PCA_ISA)	+= i2c-pca-isa.o

drivers/i2c/busses/i2c-ocores.c

···
+/*
+ * i2c-ocores.c: I2C bus driver for OpenCores I2C controller
+ * (http://www.opencores.org/projects.cgi/web/i2c/overview).
+ *
+ * Peter Korsgaard <[e-mail]>
+ *
+ * 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/config.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <linux/errno.h>
+#include <linux/platform_device.h>
+#include <linux/i2c.h>
+#include <linux/interrupt.h>
+#include <linux/wait.h>
+#include <linux/i2c-ocores.h>
+#include <asm/io.h>
+
+struct ocores_i2c {
+	void __iomem *base;
+	int regstep;
+	wait_queue_head_t wait;
+	struct i2c_adapter adap;
+	struct i2c_msg *msg;
+	int pos;
+	int nmsgs;
+	int state; /* see STATE_ */
+};
+
+/* registers */
+#define OCI2C_PRELOW		0
+#define OCI2C_PREHIGH		1
+#define OCI2C_CONTROL		2
+#define OCI2C_DATA		3
+#define OCI2C_CMD		4
+#define OCI2C_STATUS		4
+
+#define OCI2C_CTRL_IEN		0x40
+#define OCI2C_CTRL_EN		0x80
+
+#define OCI2C_CMD_START		0x91
+#define OCI2C_CMD_STOP		0x41
+#define OCI2C_CMD_READ		0x21
+#define OCI2C_CMD_WRITE		0x11
+#define OCI2C_CMD_READ_ACK	0x21
+#define OCI2C_CMD_READ_NACK	0x29
+#define OCI2C_CMD_IACK		0x01
+
+#define OCI2C_STAT_IF		0x01
+#define OCI2C_STAT_TIP		0x02
+#define OCI2C_STAT_ARBLOST	0x20
+#define OCI2C_STAT_BUSY		0x40
+#define OCI2C_STAT_NACK		0x80
+
+#define STATE_DONE		0
+#define STATE_START		1
+#define STATE_WRITE		2
+#define STATE_READ		3
+#define STATE_ERROR		4
+
+static inline void oc_setreg(struct ocores_i2c *i2c, int reg, u8 value)
+{
+	iowrite8(value, i2c->base + reg * i2c->regstep);
+}
+
+static inline u8 oc_getreg(struct ocores_i2c *i2c, int reg)
+{
+	return ioread8(i2c->base + reg * i2c->regstep);
+}
+
+static void ocores_process(struct ocores_i2c *i2c)
+{
+	struct i2c_msg *msg = i2c->msg;
+	u8 stat = oc_getreg(i2c, OCI2C_STATUS);
+
+	if ((i2c->state == STATE_DONE) || (i2c->state == STATE_ERROR)) {
+		/* stop has been sent */
+		oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_IACK);
+		wake_up(&i2c->wait);
+		return;
+	}
+
+	/* error? */
+	if (stat & OCI2C_STAT_ARBLOST) {
+		i2c->state = STATE_ERROR;
+		oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_STOP);
+		return;
+	}
+
+	if ((i2c->state == STATE_START) || (i2c->state == STATE_WRITE)) {
+		i2c->state =
+			(msg->flags & I2C_M_RD) ? STATE_READ : STATE_WRITE;
+
+		if (stat & OCI2C_STAT_NACK) {
+			i2c->state = STATE_ERROR;
+			oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_STOP);
+			return;
+		}
+	} else
+		msg->buf[i2c->pos++] = oc_getreg(i2c, OCI2C_DATA);
+
+	/* end of msg? */
+	if (i2c->pos == msg->len) {
+		i2c->nmsgs--;
+		i2c->msg++;
+		i2c->pos = 0;
+		msg = i2c->msg;
+
+		if (i2c->nmsgs) {	/* end? */
+			/* send start? */
+			if (!(msg->flags & I2C_M_NOSTART)) {
+				u8 addr = (msg->addr << 1);
+
+				if (msg->flags & I2C_M_RD)
+					addr |= 1;
+
+				i2c->state = STATE_START;
+
+				oc_setreg(i2c, OCI2C_DATA, addr);
+				oc_setreg(i2c, OCI2C_CMD,  OCI2C_CMD_START);
+				return;
+			} else
+				i2c->state = (msg->flags & I2C_M_RD)
+					? STATE_READ : STATE_WRITE;
+		} else {
+			i2c->state = STATE_DONE;
+			oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_STOP);
+			return;
+		}
+	}
+
+	if (i2c->state == STATE_READ) {
+		oc_setreg(i2c, OCI2C_CMD, i2c->pos == (msg->len-1) ?
+			  OCI2C_CMD_READ_NACK : OCI2C_CMD_READ_ACK);
+	} else {
+		oc_setreg(i2c, OCI2C_DATA, msg->buf[i2c->pos++]);
+		oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_WRITE);
+	}
+}
+
+static irqreturn_t ocores_isr(int irq, void *dev_id, struct pt_regs *regs)
+{
+	struct ocores_i2c *i2c = dev_id;
+
+	ocores_process(i2c);
+
+	return IRQ_HANDLED;
+}
+
+static int ocores_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
+{
+	struct ocores_i2c *i2c = i2c_get_adapdata(adap);
+
+	i2c->msg = msgs;
+	i2c->pos = 0;
+	i2c->nmsgs = num;
+	i2c->state = STATE_START;
+
+	oc_setreg(i2c, OCI2C_DATA,
+			(i2c->msg->addr << 1) |
+			((i2c->msg->flags & I2C_M_RD) ? 1:0));
+
+	oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_START);
+
+	if (wait_event_timeout(i2c->wait, (i2c->state == STATE_ERROR) ||
+			       (i2c->state == STATE_DONE), HZ))
+		return (i2c->state == STATE_DONE) ? num : -EIO;
+	else
+		return -ETIMEDOUT;
+}
+
+static void ocores_init(struct ocores_i2c *i2c,
+			struct ocores_i2c_platform_data *pdata)
+{
+	int prescale;
+	u8 ctrl = oc_getreg(i2c, OCI2C_CONTROL);
+
+	/* make sure the device is disabled */
+	oc_setreg(i2c, OCI2C_CONTROL, ctrl & ~(OCI2C_CTRL_EN|OCI2C_CTRL_IEN));
+
+	prescale = (pdata->clock_khz / (5*100)) - 1;
+	oc_setreg(i2c, OCI2C_PRELOW, prescale & 0xff);
+	oc_setreg(i2c, OCI2C_PREHIGH, prescale >> 8);
+
+	/* Init the device */
+	oc_setreg(i2c, OCI2C_CMD, OCI2C_CMD_IACK);
+	oc_setreg(i2c, OCI2C_CONTROL, ctrl | OCI2C_CTRL_IEN | OCI2C_CTRL_EN);
+}
+
+
+static u32 ocores_func(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+}
+
+static struct i2c_algorithm ocores_algorithm = {
+	.master_xfer	= ocores_xfer,
+	.functionality	= ocores_func,
+};
+
+static struct i2c_adapter ocores_adapter = {
+	.owner		= THIS_MODULE,
+	.name		= "i2c-ocores",
+	.class		= I2C_CLASS_HWMON,
+	.algo		= &ocores_algorithm,
+	.timeout	= 2,
+	.retries	= 1,
+};
+
+
+static int __devinit ocores_i2c_probe(struct platform_device *pdev)
+{
+	struct ocores_i2c *i2c;
+	struct ocores_i2c_platform_data *pdata;
+	struct resource *res, *res2;
+	int ret;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -ENODEV;
+
+	res2 = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
+	if (!res2)
+		return -ENODEV;
+
+	pdata = (struct ocores_i2c_platform_data*) pdev->dev.platform_data;
+	if (!pdata)
+		return -ENODEV;
+
+	i2c = kzalloc(sizeof(*i2c), GFP_KERNEL);
+	if (!i2c)
+		return -ENOMEM;
+
+	if (!request_mem_region(res->start, res->end - res->start + 1,
+				pdev->name)) {
+		dev_err(&pdev->dev, "Memory region busy\n");
+		ret = -EBUSY;
+		goto request_mem_failed;
+	}
+
+	i2c->base = ioremap(res->start, res->end - res->start + 1);
+	if (!i2c->base) {
+		dev_err(&pdev->dev, "Unable to map registers\n");
+		ret = -EIO;
+		goto map_failed;
+	}
+
+	i2c->regstep = pdata->regstep;
+	ocores_init(i2c, pdata);
+
+	init_waitqueue_head(&i2c->wait);
+	ret = request_irq(res2->start, ocores_isr, 0, pdev->name, i2c);
+	if (ret) {
+		dev_err(&pdev->dev, "Cannot claim IRQ\n");
+		goto request_irq_failed;
+	}
+
+	/* hook up driver to tree */
+	platform_set_drvdata(pdev, i2c);
+	i2c->adap = ocores_adapter;
+	i2c_set_adapdata(&i2c->adap, i2c);
+	i2c->adap.dev.parent = &pdev->dev;
+
+	/* add i2c adapter to i2c tree */
+	ret = i2c_add_adapter(&i2c->adap);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to add adapter\n");
+		goto add_adapter_failed;
+	}
+
+	return 0;
+
+add_adapter_failed:
+	free_irq(res2->start, i2c);
+request_irq_failed:
+	iounmap(i2c->base);
+map_failed:
+	release_mem_region(res->start, res->end - res->start + 1);
+request_mem_failed:
+	kfree(i2c);
+
+	return ret;
+}
+
+static int __devexit ocores_i2c_remove(struct platform_device* pdev)
+{
+	struct ocores_i2c *i2c = platform_get_drvdata(pdev);
+	struct resource *res;
+
+	/* disable i2c logic */
+	oc_setreg(i2c, OCI2C_CONTROL, oc_getreg(i2c, OCI2C_CONTROL)
+		  & ~(OCI2C_CTRL_EN|OCI2C_CTRL_IEN));
+
+	/* remove adapter & data */
+	i2c_del_adapter(&i2c->adap);
+	platform_set_drvdata(pdev, NULL);
+
+	res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
+	if (res)
+		free_irq(res->start, i2c);
+
+	iounmap(i2c->base);
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (res)
+		release_mem_region(res->start, res->end - res->start + 1);
+
+	kfree(i2c);
+
+	return 0;
+}
+
+static struct platform_driver ocores_i2c_driver = {
+	.probe  = ocores_i2c_probe,
+	.remove = __devexit_p(ocores_i2c_remove),
+	.driver = {
+		.owner = THIS_MODULE,
+		.name = "ocores-i2c",
+	},
+};
+
+static int __init ocores_i2c_init(void)
+{
+	return platform_driver_register(&ocores_i2c_driver);
+}
+
+static void __exit ocores_i2c_exit(void)
+{
+	platform_driver_unregister(&ocores_i2c_driver);
+}
+
+module_init(ocores_i2c_init);
+module_exit(ocores_i2c_exit);
+
+MODULE_AUTHOR("Peter Korsgaard <[e-mail]>");
+MODULE_DESCRIPTION("OpenCores I2C bus driver");
+MODULE_LICENSE("GPL");

include/linux/i2c-ocores.h

···
+/*
+ * i2c-ocores.h - definitions for the i2c-ocores interface
+ *
+ * Peter Korsgaard <[e-mail]>
+ *
+ * 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.
+ */
+
+#ifndef _LINUX_I2C_OCORES_H
+#define _LINUX_I2C_OCORES_H
+
+struct ocores_i2c_platform_data {
+	u32 regstep;   /* distance between registers */
+	u32 clock_khz; /* input clock in kHz */
+};
+
+#endif /* _LINUX_I2C_OCORES_H */