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Commit f3b54b9a authored by Stephen Warren's avatar Stephen Warren Committed by Wolfram Sang
Browse files

i2c: add bcm2835 driver 



This implements a very basic I2C host driver for the BCM2835 SoC. Missing
features so far are:

* 10-bit addressing.
* DMA.

Reviewed-by: default avatarGrant Likely <grant.likely@secretlab.ca>
Signed-off-by: default avatarStephen Warren <swarren@wwwdotorg.org>
Signed-off-by: default avatarWolfram Sang <wolfram@the-dreams.de>
parent cb7f07a4

Documentation/devicetree/bindings/i2c/brcm,bcm2835-i2c.txt

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Broadcom BCM2835 I2C controller



Required properties:

- compatible : Should be "brcm,bcm2835-i2c".

- reg: Should contain register location and length.

- interrupts: Should contain interrupt.

- clocks : The clock feeding the I2C controller.



Recommended properties:

- clock-frequency : desired I2C bus clock frequency in Hz.



Example:



i2c@20205000 {

	compatible = "brcm,bcm2835-i2c";

	reg = <0x7e205000 0x1000>;

	interrupts = <2 21>;

	clocks = <&clk_i2c>;

	clock-frequency = <100000>;

};

drivers/i2c/busses/Kconfig

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@@ -330,6 +330,18 @@ config I2C_AU1550 
	  This driver can also be built as a module.  If so, the module

	  will be called i2c-au1550.



config I2C_BCM2835

	tristate "Broadcom BCM2835 I2C controller"

	depends on ARCH_BCM2835

	help

	  If you say yes to this option, support will be included for the

	  BCM2835 I2C controller.



	  If you don't know what to do here, say N.



	  This support is also available as a module.  If so, the module

	  will be called i2c-bcm2835.



config I2C_BLACKFIN_TWI

	tristate "Blackfin TWI I2C support"

	depends on BLACKFIN

drivers/i2c/busses/Makefile

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@@ -31,6 +31,7 @@ obj-$(CONFIG_I2C_POWERMAC) += i2c-powermac.o 
# Embedded system I2C/SMBus host controller drivers

obj-$(CONFIG_I2C_AT91)		+= i2c-at91.o

obj-$(CONFIG_I2C_AU1550)	+= i2c-au1550.o

obj-$(CONFIG_I2C_BCM2835)	+= i2c-bcm2835.o

obj-$(CONFIG_I2C_BLACKFIN_TWI)	+= i2c-bfin-twi.o

obj-$(CONFIG_I2C_CBUS_GPIO)	+= i2c-cbus-gpio.o

obj-$(CONFIG_I2C_CPM)		+= i2c-cpm.o

drivers/i2c/busses/i2c-bcm2835.c

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/*

 * BCM2835 master mode driver

 *

 * This software is licensed under the terms of the GNU General Public

 * License version 2, as published by the Free Software Foundation, and

 * may be copied, distributed, and modified under those terms.

 *

 * 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.

 */



#include <linux/clk.h>

#include <linux/completion.h>

#include <linux/err.h>

#include <linux/i2c.h>

#include <linux/interrupt.h>

#include <linux/io.h>

#include <linux/module.h>

#include <linux/platform_device.h>

#include <linux/slab.h>



#define BCM2835_I2C_C		0x0

#define BCM2835_I2C_S		0x4

#define BCM2835_I2C_DLEN	0x8

#define BCM2835_I2C_A		0xc

#define BCM2835_I2C_FIFO	0x10

#define BCM2835_I2C_DIV		0x14

#define BCM2835_I2C_DEL		0x18

#define BCM2835_I2C_CLKT	0x1c



#define BCM2835_I2C_C_READ	BIT(0)

#define BCM2835_I2C_C_CLEAR	BIT(4) /* bits 4 and 5 both clear */

#define BCM2835_I2C_C_ST	BIT(7)

#define BCM2835_I2C_C_INTD	BIT(8)

#define BCM2835_I2C_C_INTT	BIT(9)

#define BCM2835_I2C_C_INTR	BIT(10)

#define BCM2835_I2C_C_I2CEN	BIT(15)



#define BCM2835_I2C_S_TA	BIT(0)

#define BCM2835_I2C_S_DONE	BIT(1)

#define BCM2835_I2C_S_TXW	BIT(2)

#define BCM2835_I2C_S_RXR	BIT(3)

#define BCM2835_I2C_S_TXD	BIT(4)

#define BCM2835_I2C_S_RXD	BIT(5)

#define BCM2835_I2C_S_TXE	BIT(6)

#define BCM2835_I2C_S_RXF	BIT(7)

#define BCM2835_I2C_S_ERR	BIT(8)

#define BCM2835_I2C_S_CLKT	BIT(9)

#define BCM2835_I2C_S_LEN	BIT(10) /* Fake bit for SW error reporting */



#define BCM2835_I2C_TIMEOUT (msecs_to_jiffies(1000))



struct bcm2835_i2c_dev {

	struct device *dev;

	void __iomem *regs;

	struct clk *clk;

	int irq;

	struct i2c_adapter adapter;

	struct completion completion;

	u32 msg_err;

	u8 *msg_buf;

	size_t msg_buf_remaining;

};



static inline void bcm2835_i2c_writel(struct bcm2835_i2c_dev *i2c_dev,

				      u32 reg, u32 val)

{

	writel(val, i2c_dev->regs + reg);

}



static inline u32 bcm2835_i2c_readl(struct bcm2835_i2c_dev *i2c_dev, u32 reg)

{

	return readl(i2c_dev->regs + reg);

}



static void bcm2835_fill_txfifo(struct bcm2835_i2c_dev *i2c_dev)

{

	u32 val;



	while (i2c_dev->msg_buf_remaining) {

		val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);

		if (!(val & BCM2835_I2C_S_TXD))

			break;

		bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_FIFO,

				   *i2c_dev->msg_buf);

		i2c_dev->msg_buf++;

		i2c_dev->msg_buf_remaining--;

	}

}



static void bcm2835_drain_rxfifo(struct bcm2835_i2c_dev *i2c_dev)

{

	u32 val;



	while (i2c_dev->msg_buf_remaining) {

		val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);

		if (!(val & BCM2835_I2C_S_RXD))

			break;

		*i2c_dev->msg_buf = bcm2835_i2c_readl(i2c_dev,

						      BCM2835_I2C_FIFO);

		i2c_dev->msg_buf++;

		i2c_dev->msg_buf_remaining--;

	}

}



static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data)

{

	struct bcm2835_i2c_dev *i2c_dev = data;

	u32 val, err;



	val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);

	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_S, val);



	err = val & (BCM2835_I2C_S_CLKT | BCM2835_I2C_S_ERR);

	if (err) {

		i2c_dev->msg_err = err;

		complete(&i2c_dev->completion);

		return IRQ_HANDLED;

	}



	if (val & BCM2835_I2C_S_RXD) {

		bcm2835_drain_rxfifo(i2c_dev);

		if (!(val & BCM2835_I2C_S_DONE))

			return IRQ_HANDLED;

	}



	if (val & BCM2835_I2C_S_DONE) {

		if (i2c_dev->msg_buf_remaining)

			i2c_dev->msg_err = BCM2835_I2C_S_LEN;

		else

			i2c_dev->msg_err = 0;

		complete(&i2c_dev->completion);

		return IRQ_HANDLED;

	}



	if (val & BCM2835_I2C_S_TXD) {

		bcm2835_fill_txfifo(i2c_dev);

		return IRQ_HANDLED;

	}



	return IRQ_NONE;

}



static int bcm2835_i2c_xfer_msg(struct bcm2835_i2c_dev *i2c_dev,

				struct i2c_msg *msg)

{

	u32 c;

	int time_left;



	i2c_dev->msg_buf = msg->buf;

	i2c_dev->msg_buf_remaining = msg->len;

	INIT_COMPLETION(i2c_dev->completion);



	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, BCM2835_I2C_C_CLEAR);



	if (msg->flags & I2C_M_RD) {

		c = BCM2835_I2C_C_READ | BCM2835_I2C_C_INTR;

	} else {

		c = BCM2835_I2C_C_INTT;

		bcm2835_fill_txfifo(i2c_dev);

	}

	c |= BCM2835_I2C_C_ST | BCM2835_I2C_C_INTD | BCM2835_I2C_C_I2CEN;



	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_A, msg->addr);

	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DLEN, msg->len);

	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, c);



	time_left = wait_for_completion_timeout(&i2c_dev->completion,

						BCM2835_I2C_TIMEOUT);

	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, BCM2835_I2C_C_CLEAR);

	if (!time_left) {

		dev_err(i2c_dev->dev, "i2c transfer timed out\n");

		return -ETIMEDOUT;

	}



	if (likely(!i2c_dev->msg_err))

		return 0;



	if ((i2c_dev->msg_err & BCM2835_I2C_S_ERR) &&

	    (msg->flags & I2C_M_IGNORE_NAK))

		return 0;



	dev_err(i2c_dev->dev, "i2c transfer failed: %x\n", i2c_dev->msg_err);



	if (i2c_dev->msg_err & BCM2835_I2C_S_ERR)

		return -EREMOTEIO;

	else

		return -EIO;

}



static int bcm2835_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],

			    int num)

{

	struct bcm2835_i2c_dev *i2c_dev = i2c_get_adapdata(adap);

	int i;

	int ret = 0;



	for (i = 0; i < num; i++) {

		ret = bcm2835_i2c_xfer_msg(i2c_dev, &msgs[i]);

		if (ret)

			break;

	}



	return ret ?: i;

}



static u32 bcm2835_i2c_func(struct i2c_adapter *adap)

{

	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;

}



static const struct i2c_algorithm bcm2835_i2c_algo = {

	.master_xfer	= bcm2835_i2c_xfer,

	.functionality	= bcm2835_i2c_func,

};



static int bcm2835_i2c_probe(struct platform_device *pdev)

{

	struct bcm2835_i2c_dev *i2c_dev;

	struct resource *mem, *requested, *irq;

	u32 bus_clk_rate, divider;

	int ret;

	struct i2c_adapter *adap;



	i2c_dev = devm_kzalloc(&pdev->dev, sizeof(*i2c_dev), GFP_KERNEL);

	if (!i2c_dev) {

		dev_err(&pdev->dev, "Cannot allocate i2c_dev\n");

		return -ENOMEM;

	}

	platform_set_drvdata(pdev, i2c_dev);

	i2c_dev->dev = &pdev->dev;

	init_completion(&i2c_dev->completion);



	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);

	if (!mem) {

		dev_err(&pdev->dev, "No mem resource\n");

		return -ENODEV;

	}



	requested = devm_request_mem_region(&pdev->dev, mem->start,

					    resource_size(mem),

					    dev_name(&pdev->dev));

	if (!requested) {

		dev_err(&pdev->dev, "Could not claim register region\n");

		return -EBUSY;

	}



	i2c_dev->regs = devm_ioremap(&pdev->dev, mem->start,

				     resource_size(mem));

	if (!i2c_dev->regs) {

		dev_err(&pdev->dev, "Could not map registers\n");

		return -ENOMEM;

	}



	i2c_dev->clk = devm_clk_get(&pdev->dev, NULL);

	if (IS_ERR(i2c_dev->clk)) {

		dev_err(&pdev->dev, "Could not get clock\n");

		return PTR_ERR(i2c_dev->clk);

	}



	ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",

				   &bus_clk_rate);

	if (ret < 0) {

		dev_warn(&pdev->dev,

			 "Could not read clock-frequency property\n");

		bus_clk_rate = 100000;

	}



	divider = DIV_ROUND_UP(clk_get_rate(i2c_dev->clk), bus_clk_rate);

	/*

	 * Per the datasheet, the register is always interpreted as an even

	 * number, by rounding down. In other words, the LSB is ignored. So,

	 * if the LSB is set, increment the divider to avoid any issue.

	 */

	if (divider & 1)

		divider++;

	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DIV, divider);



	irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);

	if (!irq) {

		dev_err(&pdev->dev, "No IRQ resource\n");

		return -ENODEV;

	}

	i2c_dev->irq = irq->start;



	ret = request_irq(i2c_dev->irq, bcm2835_i2c_isr, IRQF_SHARED,

			  dev_name(&pdev->dev), i2c_dev);

	if (ret) {

		dev_err(&pdev->dev, "Could not request IRQ\n");

		return -ENODEV;

	}



	adap = &i2c_dev->adapter;

	i2c_set_adapdata(adap, i2c_dev);

	adap->owner = THIS_MODULE;

	adap->class = I2C_CLASS_HWMON;

	strlcpy(adap->name, "bcm2835 I2C adapter", sizeof(adap->name));

	adap->algo = &bcm2835_i2c_algo;

	adap->dev.parent = &pdev->dev;



	bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, 0);



	ret = i2c_add_adapter(adap);

	if (ret)

		free_irq(i2c_dev->irq, i2c_dev);



	return ret;

}



static int bcm2835_i2c_remove(struct platform_device *pdev)

{

	struct bcm2835_i2c_dev *i2c_dev = platform_get_drvdata(pdev);



	free_irq(i2c_dev->irq, i2c_dev);

	i2c_del_adapter(&i2c_dev->adapter);



	return 0;

}



static const struct of_device_id bcm2835_i2c_of_match[] = {

	{ .compatible = "brcm,bcm2835-i2c" },

	{},

};

MODULE_DEVICE_TABLE(of, bcm2835_i2c_of_match);



static struct platform_driver bcm2835_i2c_driver = {

	.probe		= bcm2835_i2c_probe,

	.remove		= bcm2835_i2c_remove,

	.driver		= {

		.name	= "i2c-bcm2835",

		.owner	= THIS_MODULE,

		.of_match_table = bcm2835_i2c_of_match,

	},

};

module_platform_driver(bcm2835_i2c_driver);



MODULE_AUTHOR("Stephen Warren <swarren@wwwdotorg.org>");

MODULE_DESCRIPTION("BCM2835 I2C bus adapter");

MODULE_LICENSE("GPL v2");

MODULE_ALIAS("platform:i2c-bcm2835");