[i2c] [PATCH] AT91 I2C bus driver

Andrew Victor andrew at sanpeople.com
Thu Oct 19 18:33:25 CEST 2006


hi,

This patch adds support for the I2C (Two-wire interface) controller
integrated in the Atmel AT91RM9200 processor.  This driver should also
be usable on the Atmel AT91SAM9261 and AT91SAM9260 processors.

Major changes from previous version:
 - Memory region is ioremapped.
 - Fix for problem reported by Mike Wolfram.
 - Replace BUG_ON() with printk() and set clock-divisor to a valid value


Signed-off-by: Andrew Victor <andrew at sanpeople.com>




diff -urN -x CVS linux-2.6.19-rc2.orig/drivers/i2c/busses/Kconfig linux-2.6.19/drivers/i2c/busses/Kconfig
--- linux-2.6.19-rc2.orig/drivers/i2c/busses/Kconfig	Thu Oct 19 16:31:37 2006
+++ linux-2.6.19/drivers/i2c/busses/Kconfig	Thu Oct 12 17:07:38 2006
@@ -74,6 +74,13 @@
 	  This driver can also be built as a module.  If so, the module
 	  will be called i2c-amd8111.
 
+config I2C_AT91
+	tristate "Atmel AT91 I2C Two-Wire interface (TWI)"
+	depends on I2C && ARCH_AT91 && EXPERIMENTAL
+	help
+	  This supports the use of the I2C interface on Atmel AT91
+	  processors.
+
 config I2C_AU1550
 	tristate "Au1550/Au1200 SMBus interface"
 	depends on I2C && (SOC_AU1550 || SOC_AU1200)
diff -urN -x CVS linux-2.6.19-rc2.orig/drivers/i2c/busses/Makefile linux-2.6.19/drivers/i2c/busses/Makefile
--- linux-2.6.19-rc2.orig/drivers/i2c/busses/Makefile	Thu Oct 19 16:31:37 2006
+++ linux-2.6.19/drivers/i2c/busses/Makefile	Thu Oct 12 17:07:38 2006
@@ -8,6 +8,7 @@
 obj-$(CONFIG_I2C_AMD756)	+= i2c-amd756.o
 obj-$(CONFIG_I2C_AMD756_S4882)	+= i2c-amd756-s4882.o
 obj-$(CONFIG_I2C_AMD8111)	+= i2c-amd8111.o
+obj-$(CONFIG_I2C_AT91)		+= i2c-at91.o
 obj-$(CONFIG_I2C_AU1550)	+= i2c-au1550.o
 obj-$(CONFIG_I2C_ELEKTOR)	+= i2c-elektor.o
 obj-$(CONFIG_I2C_HYDRA)		+= i2c-hydra.o
diff -urN -x CVS linux-2.6.19-rc2.orig/drivers/i2c/busses/i2c-at91.c linux-2.6.19/drivers/i2c/busses/i2c-at91.c
--- linux-2.6.19-rc2.orig/drivers/i2c/busses/i2c-at91.c	Thu Jan  1 02:00:00 1970
+++ linux-2.6.19/drivers/i2c/busses/i2c-at91.c	Thu Oct 12 17:07:38 2006
@@ -0,0 +1,323 @@
+/*
+    i2c Support for Atmel's AT91 Two-Wire Interface (TWI)
+
+    Copyright (C) 2004 Rick Bronson
+    Converted to 2.6 by Andrew Victor <andrew at sanpeople.com>
+
+    Borrowed heavily from original work by:
+    Copyright (C) 2000 Philip Edelbrock <phil at stimpy.netroedge.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.
+*/
+
+#include <linux/module.h>
+#include <linux/version.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/pci.h>
+#include <linux/types.h>
+#include <linux/delay.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/clk.h>
+#include <linux/platform_device.h>
+
+#include <asm/io.h>
+
+#include <asm/arch/at91rm9200_twi.h>
+#include <asm/arch/board.h>
+#include <asm/arch/system.h>
+
+#define TWI_CLOCK		100000		/* Hz. max 400 Kbits/sec */
+
+
+static struct clk *twi_clk;
+static void __iomem *twi_base;
+
+#define at91_twi_read(reg)		__raw_readl(twi_base + (reg))
+#define at91_twi_write(reg, val)	__raw_writel((val), twi_base + (reg))
+
+
+/*
+ * Initialize the TWI hardware registers.
+ */
+static void __devinit at91_twi_hwinit(void)
+{
+	unsigned long cdiv, ckdiv;
+
+	at91_twi_write(AT91_TWI_IDR, 0xffffffff);	/* Disable all interrupts */
+	at91_twi_write(AT91_TWI_CR, AT91_TWI_SWRST);	/* Reset peripheral */
+	at91_twi_write(AT91_TWI_CR, AT91_TWI_MSEN);	/* Set Master mode */
+
+	/* Calcuate clock dividers */
+	cdiv = (clk_get_rate(twi_clk) / (2 * TWI_CLOCK)) - 3;
+	cdiv = cdiv + 1;	/* round up */
+	ckdiv = 0;
+	while (cdiv > 255) {
+		ckdiv++;
+		cdiv = cdiv >> 1;
+	}
+
+	if (arch_identify() == ARCH_ID_AT91RM9200) {	/* AT91RM9200 Errata #22 */
+		if (ckdiv > 5) {
+			printk(KERN_ERR "AT91 I2C: Invalid TWI_CLOCK value specified!\n");
+			ckdiv = 5;
+		}
+	}
+
+	at91_twi_write(AT91_TWI_CWGR, (ckdiv << 16) | (cdiv << 8) | cdiv);
+}
+
+/*
+ * Poll the i2c status register until the specified bit is set.
+ * Returns 0 if timed out (100 msec).
+ */
+static short at91_poll_status(unsigned long bit)
+{
+	int loop_cntr = 10000;
+
+	do {
+		udelay(10);
+	} while (!(at91_twi_read(AT91_TWI_SR) & bit) && (--loop_cntr > 0));
+
+	return (loop_cntr > 0);
+}
+
+static int xfer_read(struct i2c_adapter *adap, unsigned char *buf, int length)
+{
+	/* Send Start */
+	at91_twi_write(AT91_TWI_CR, AT91_TWI_START);
+
+	/* Read data */
+	while (length--) {
+		if (!length)
+			at91_twi_write(AT91_TWI_CR, AT91_TWI_STOP);	/* need to send Stop before reading last byte */
+		if (!at91_poll_status(AT91_TWI_RXRDY)) {
+			dev_dbg(&adap->dev, "RXRDY timeout\n");
+			return -ETIMEDOUT;
+		}
+		*buf++ = (at91_twi_read(AT91_TWI_RHR) & 0xff);
+	}
+
+	return 0;
+}
+
+static int xfer_write(struct i2c_adapter *adap, unsigned char *buf, int length)
+{
+	/* Load first byte into transmitter */
+	at91_twi_write(AT91_TWI_THR, *buf++);
+
+	/* Send Start */
+	at91_twi_write(AT91_TWI_CR, AT91_TWI_START);
+
+	do {
+		if (!at91_poll_status(AT91_TWI_TXRDY)) {
+			dev_dbg(&adap->dev, "TXRDY timeout\n");
+			return -ETIMEDOUT;
+		}
+
+		length--;	/* byte was transmitted */
+
+		if (length > 0)		/* more data to send? */
+			at91_twi_write(AT91_TWI_THR, *buf++);
+	} while (length);
+
+	/* Send Stop */
+	at91_twi_write(AT91_TWI_CR, AT91_TWI_STOP);
+
+	return 0;
+}
+
+/*
+ * Generic i2c master transfer entrypoint.
+ */
+static int at91_xfer(struct i2c_adapter *adap, struct i2c_msg *pmsg, int num)
+{
+	int i, ret;
+
+	dev_dbg(&adap->dev, "at91_xfer: processing %d messages:\n", num);
+
+	for (i = 0; i < num; i++) {
+		dev_dbg(&adap->dev, " #%d: %sing %d byte%s %s 0x%02x\n", i,
+			pmsg->flags & I2C_M_RD ? "read" : "writ",
+			pmsg->len, pmsg->len > 1 ? "s" : "",
+			pmsg->flags & I2C_M_RD ? "from" : "to",	pmsg->addr);
+
+		/*
+		 * Set the TWI Master Mode Register:
+		 *  We do _not_ use Atmel's feature of storing the "internal device address"
+		 *  in TWI_IADR.  Thus the IADRSZ bits in TWI_MMR are set to zero.
+		 *  Instead the "internal device address" has to be written using a seperate
+		 *  i2c message.
+		 *  See http://lists.arm.linux.org.uk/pipermail/linux-arm-kernel/2004-September/024411.html
+		 */
+		at91_twi_write(AT91_TWI_MMR, (pmsg->addr << 16)
+			| ((pmsg->flags & I2C_M_RD) ? AT91_TWI_MREAD : 0));
+
+		if (pmsg->len && pmsg->buf) {	/* sanity check */
+			if (pmsg->flags & I2C_M_RD)
+				ret = xfer_read(adap, pmsg->buf, pmsg->len);
+			else
+				ret = xfer_write(adap, pmsg->buf, pmsg->len);
+
+			if (ret)
+				return ret;
+
+			/* Wait until transfer is finished */
+			if (!at91_poll_status(AT91_TWI_TXCOMP)) {
+				dev_dbg(&adap->dev, "TXCOMP timeout\n");
+				return -ETIMEDOUT;
+			}
+		}
+		dev_dbg(&adap->dev, "transfer complete\n");
+		pmsg++;		/* next message */
+	}
+	return i;
+}
+
+/*
+ * Return list of supported functionality.
+ */
+static u32 at91_func(struct i2c_adapter *adapter)
+{
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+}
+
+static struct i2c_algorithm at91_algorithm = {
+	.master_xfer	= at91_xfer,
+	.functionality	= at91_func,
+};
+
+/*
+ * Main initialization routine.
+ */
+static int __devinit at91_i2c_probe(struct platform_device *pdev)
+{
+	struct i2c_adapter *adapter;
+	struct resource *res;
+	int rc;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res)
+		return -ENXIO;
+	
+	if (!request_mem_region(res->start, res->end - res->start + 1, "at91_i2c"))
+		return -EBUSY;
+		
+	twi_base = ioremap(res->start, res->end - res->start + 1);
+	if (!twi_base) {
+		release_mem_region(res->start, res->end - res->start + 1);
+		return -ENOMEM;
+	}
+
+	twi_clk = clk_get(NULL, "twi_clk");
+	if (IS_ERR(twi_clk)) {
+		dev_err(&pdev->dev, "no clock defined\n");
+		iounmap(twi_base);
+		release_mem_region(res->start, res->end - res->start + 1);
+		return -ENODEV;
+	}
+
+	adapter = kzalloc(sizeof(struct i2c_adapter), GFP_KERNEL);
+	if (adapter == NULL) {
+		dev_err(&pdev->dev, "can't allocate inteface!\n");
+		clk_put(twi_clk);
+		iounmap(twi_base);
+		release_mem_region(res->start, res->end - res->start + 1);
+		return -ENOMEM;
+	}
+	sprintf(adapter->name, "AT91");
+	adapter->algo = &at91_algorithm;
+	adapter->class = I2C_CLASS_HWMON;
+	adapter->dev.parent = &pdev->dev;
+
+	platform_set_drvdata(pdev, adapter);
+
+	clk_enable(twi_clk);		/* enable peripheral clock */
+	at91_twi_hwinit();		/* initialize TWI controller */
+
+	rc = i2c_add_adapter(adapter);
+	if (rc) {
+		dev_err(&pdev->dev, "Adapter %s registration failed\n",
+				adapter->name);
+		platform_set_drvdata(pdev, NULL);
+		kfree(adapter);
+		clk_disable(twi_clk);
+		clk_put(twi_clk);
+		iounmap(twi_base);
+		release_mem_region(res->start, res->end - res->start + 1);
+	} else
+		dev_info(&pdev->dev, "AT91 i2c bus driver.\n");
+
+	return rc;
+}
+
+static int __devexit at91_i2c_remove(struct platform_device *pdev)
+{
+	struct i2c_adapter *adapter = platform_get_drvdata(pdev);
+	struct resource *res;
+	int rc;
+
+	rc = i2c_del_adapter(adapter);
+	platform_set_drvdata(pdev, NULL);
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	iounmap(twi_base);
+	release_mem_region(res->start, res->end - res->start + 1);
+
+	clk_disable(twi_clk);		/* disable peripheral clock */
+	clk_put(twi_clk);
+
+	return rc;
+}
+
+#ifdef CONFIG_PM
+
+/* NOTE: could save a few mA by keeping clock off outside of at91_xfer... */
+
+static int at91_i2c_suspend(struct platform_device *pdev, pm_message_t mesg)
+{
+	clk_disable(twi_clk);
+	return 0;
+}
+
+static int at91_i2c_resume(struct platform_device *pdev)
+{
+	return clk_enable(twi_clk);
+}
+
+#else
+#define at91_i2c_suspend	NULL
+#define at91_i2c_resume		NULL
+#endif
+
+static struct platform_driver at91_i2c_driver = {
+	.probe		= at91_i2c_probe,
+	.remove		= __devexit_p(at91_i2c_remove),
+	.suspend	= at91_i2c_suspend,
+	.resume		= at91_i2c_resume,
+	.driver		= {
+		.name	= "at91_i2c",
+		.owner	= THIS_MODULE,
+	},
+};
+
+static int __init at91_i2c_init(void)
+{
+	return platform_driver_register(&at91_i2c_driver);
+}
+
+static void __exit at91_i2c_exit(void)
+{
+	platform_driver_unregister(&at91_i2c_driver);
+}
+
+module_init(at91_i2c_init);
+module_exit(at91_i2c_exit);
+
+MODULE_AUTHOR("Rick Bronson");
+MODULE_DESCRIPTION("I2C (TWI) driver for Atmel AT91");
+MODULE_LICENSE("GPL");






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