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linux/drivers/i2c/busses/i2c-lpc2k.c
Joachim Eastwood 3f9c37a0c9 i2c: lpc2k: add driver 
Add support for the I2C controller found on several NXP devices
including LPC2xxx, LPC178x/7x and LPC18xx/43xx. The controller
is implemented as a state machine and the driver act upon the
state changes when the bus is accessed.

The I2C controller supports master/slave operation, bus
arbitration, programmable clock rate, and speeds up to 1 Mbit/s.

Signed-off-by: Joachim Eastwood <manabian@gmail.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
2015-08-24 14:05:18 +02:00

514 lines
12 KiB
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/*
* Copyright (C) 2011 NXP Semiconductors
*
* Code portions referenced from the i2x-pxa and i2c-pnx drivers
*
* Make SMBus byte and word transactions work on LPC178x/7x
* Copyright (c) 2012
* Alexander Potashev, Emcraft Systems, aspotashev@emcraft.com
* Anton Protopopov, Emcraft Systems, antonp@emcraft.com
*
* Copyright (C) 2015 Joachim Eastwood <manabian@gmail.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/clk.h>
#include <linux/errno.h>
#include <linux/i2c.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/sched.h>
#include <linux/time.h>
/* LPC24xx register offsets and bits */
#define LPC24XX_I2CONSET 0x00
#define LPC24XX_I2STAT 0x04
#define LPC24XX_I2DAT 0x08
#define LPC24XX_I2ADDR 0x0c
#define LPC24XX_I2SCLH 0x10
#define LPC24XX_I2SCLL 0x14
#define LPC24XX_I2CONCLR 0x18
#define LPC24XX_AA BIT(2)
#define LPC24XX_SI BIT(3)
#define LPC24XX_STO BIT(4)
#define LPC24XX_STA BIT(5)
#define LPC24XX_I2EN BIT(6)
#define LPC24XX_STO_AA (LPC24XX_STO | LPC24XX_AA)
#define LPC24XX_CLEAR_ALL (LPC24XX_AA | LPC24XX_SI | LPC24XX_STO | \
LPC24XX_STA | LPC24XX_I2EN)
/* I2C SCL clock has different duty cycle depending on mode */
#define I2C_STD_MODE_DUTY 46
#define I2C_FAST_MODE_DUTY 36
#define I2C_FAST_MODE_PLUS_DUTY 38
/*
* 26 possible I2C status codes, but codes applicable only
* to master are listed here and used in this driver
*/
enum {
M_BUS_ERROR = 0x00,
M_START = 0x08,
M_REPSTART = 0x10,
MX_ADDR_W_ACK = 0x18,
MX_ADDR_W_NACK = 0x20,
MX_DATA_W_ACK = 0x28,
MX_DATA_W_NACK = 0x30,
M_DATA_ARB_LOST = 0x38,
MR_ADDR_R_ACK = 0x40,
MR_ADDR_R_NACK = 0x48,
MR_DATA_R_ACK = 0x50,
MR_DATA_R_NACK = 0x58,
M_I2C_IDLE = 0xf8,
};
struct lpc2k_i2c {
void __iomem *base;
struct clk *clk;
int irq;
wait_queue_head_t wait;
struct i2c_adapter adap;
struct i2c_msg *msg;
int msg_idx;
int msg_status;
int is_last;
};
static void i2c_lpc2k_reset(struct lpc2k_i2c *i2c)
{
/* Will force clear all statuses */
writel(LPC24XX_CLEAR_ALL, i2c->base + LPC24XX_I2CONCLR);
writel(0, i2c->base + LPC24XX_I2ADDR);
writel(LPC24XX_I2EN, i2c->base + LPC24XX_I2CONSET);
}
static int i2c_lpc2k_clear_arb(struct lpc2k_i2c *i2c)
{
unsigned long timeout = jiffies + msecs_to_jiffies(1000);
/*
* If the transfer needs to abort for some reason, we'll try to
* force a stop condition to clear any pending bus conditions
*/
writel(LPC24XX_STO, i2c->base + LPC24XX_I2CONSET);
/* Wait for status change */
while (readl(i2c->base + LPC24XX_I2STAT) != M_I2C_IDLE) {
if (time_after(jiffies, timeout)) {
/* Bus was not idle, try to reset adapter */
i2c_lpc2k_reset(i2c);
return -EBUSY;
}
cpu_relax();
}
return 0;
}
static void i2c_lpc2k_pump_msg(struct lpc2k_i2c *i2c)
{
unsigned char data;
u32 status;
/*
* I2C in the LPC2xxx series is basically a state machine.
* Just run through the steps based on the current status.
*/
status = readl(i2c->base + LPC24XX_I2STAT);
switch (status) {
case M_START:
case M_REPSTART:
/* Start bit was just sent out, send out addr and dir */
data = i2c->msg->addr << 1;
if (i2c->msg->flags & I2C_M_RD)
data |= 1;
writel(data, i2c->base + LPC24XX_I2DAT);
writel(LPC24XX_STA, i2c->base + LPC24XX_I2CONCLR);
break;
case MX_ADDR_W_ACK:
case MX_DATA_W_ACK:
/*
* Address or data was sent out with an ACK. If there is more
* data to send, send it now
*/
if (i2c->msg_idx < i2c->msg->len) {
writel(i2c->msg->buf[i2c->msg_idx],
i2c->base + LPC24XX_I2DAT);
} else if (i2c->is_last) {
/* Last message, send stop */
writel(LPC24XX_STO_AA, i2c->base + LPC24XX_I2CONSET);
writel(LPC24XX_SI, i2c->base + LPC24XX_I2CONCLR);
i2c->msg_status = 0;
disable_irq_nosync(i2c->irq);
} else {
i2c->msg_status = 0;
disable_irq_nosync(i2c->irq);
}
i2c->msg_idx++;
break;
case MR_ADDR_R_ACK:
/* Receive first byte from slave */
if (i2c->msg->len == 1) {
/* Last byte, return NACK */
writel(LPC24XX_AA, i2c->base + LPC24XX_I2CONCLR);
} else {
/* Not last byte, return ACK */
writel(LPC24XX_AA, i2c->base + LPC24XX_I2CONSET);
}
writel(LPC24XX_STA, i2c->base + LPC24XX_I2CONCLR);
break;
case MR_DATA_R_NACK:
/*
* The I2C shows NACK status on reads, so we need to accept
* the NACK as an ACK here. This should be ok, as the real
* BACK would of been caught on the address write.
*/
case MR_DATA_R_ACK:
/* Data was received */
if (i2c->msg_idx < i2c->msg->len) {
i2c->msg->buf[i2c->msg_idx] =
readl(i2c->base + LPC24XX_I2DAT);
}
/* If transfer is done, send STOP */
if (i2c->msg_idx >= i2c->msg->len - 1 && i2c->is_last) {
writel(LPC24XX_STO_AA, i2c->base + LPC24XX_I2CONSET);
writel(LPC24XX_SI, i2c->base + LPC24XX_I2CONCLR);
i2c->msg_status = 0;
}
/* Message is done */
if (i2c->msg_idx >= i2c->msg->len - 1) {
i2c->msg_status = 0;
disable_irq_nosync(i2c->irq);
}
/*
* One pre-last data input, send NACK to tell the slave that
* this is going to be the last data byte to be transferred.
*/
if (i2c->msg_idx >= i2c->msg->len - 2) {
/* One byte left to receive - NACK */
writel(LPC24XX_AA, i2c->base + LPC24XX_I2CONCLR);
} else {
/* More than one byte left to receive - ACK */
writel(LPC24XX_AA, i2c->base + LPC24XX_I2CONSET);
}
writel(LPC24XX_STA, i2c->base + LPC24XX_I2CONCLR);
i2c->msg_idx++;
break;
case MX_ADDR_W_NACK:
case MX_DATA_W_NACK:
case MR_ADDR_R_NACK:
/* NACK processing is done */
writel(LPC24XX_STO_AA, i2c->base + LPC24XX_I2CONSET);
i2c->msg_status = -ENXIO;
disable_irq_nosync(i2c->irq);
break;
case M_DATA_ARB_LOST:
/* Arbitration lost */
i2c->msg_status = -EAGAIN;
/* Release the I2C bus */
writel(LPC24XX_STA | LPC24XX_STO, i2c->base + LPC24XX_I2CONCLR);
disable_irq_nosync(i2c->irq);
break;
default:
/* Unexpected statuses */
i2c->msg_status = -EIO;
disable_irq_nosync(i2c->irq);
break;
}
/* Exit on failure or all bytes transferred */
if (i2c->msg_status != -EBUSY)
wake_up(&i2c->wait);
/*
* If `msg_status` is zero, then `lpc2k_process_msg()`
* is responsible for clearing the SI flag.
*/
if (i2c->msg_status != 0)
writel(LPC24XX_SI, i2c->base + LPC24XX_I2CONCLR);
}
static int lpc2k_process_msg(struct lpc2k_i2c *i2c, int msgidx)
{
/* A new transfer is kicked off by initiating a start condition */
if (!msgidx) {
writel(LPC24XX_STA, i2c->base + LPC24XX_I2CONSET);
} else {
/*
* A multi-message I2C transfer continues where the
* previous I2C transfer left off and uses the
* current condition of the I2C adapter.
*/
if (unlikely(i2c->msg->flags & I2C_M_NOSTART)) {
WARN_ON(i2c->msg->len == 0);
if (!(i2c->msg->flags & I2C_M_RD)) {
/* Start transmit of data */
writel(i2c->msg->buf[0],
i2c->base + LPC24XX_I2DAT);
i2c->msg_idx++;
}
} else {
/* Start or repeated start */
writel(LPC24XX_STA, i2c->base + LPC24XX_I2CONSET);
}
writel(LPC24XX_SI, i2c->base + LPC24XX_I2CONCLR);
}
enable_irq(i2c->irq);
/* Wait for transfer completion */
if (wait_event_timeout(i2c->wait, i2c->msg_status != -EBUSY,
msecs_to_jiffies(1000)) == 0) {
disable_irq_nosync(i2c->irq);
return -ETIMEDOUT;
}
return i2c->msg_status;
}
static int i2c_lpc2k_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
int msg_num)
{
struct lpc2k_i2c *i2c = i2c_get_adapdata(adap);
int ret, i;
u32 stat;
/* Check for bus idle condition */
stat = readl(i2c->base + LPC24XX_I2STAT);
if (stat != M_I2C_IDLE) {
/* Something is holding the bus, try to clear it */
return i2c_lpc2k_clear_arb(i2c);
}
/* Process a single message at a time */
for (i = 0; i < msg_num; i++) {
/* Save message pointer and current message data index */
i2c->msg = &msgs[i];
i2c->msg_idx = 0;
i2c->msg_status = -EBUSY;
i2c->is_last = (i == (msg_num - 1));
ret = lpc2k_process_msg(i2c, i);
if (ret)
return ret;
}
return msg_num;
}
static irqreturn_t i2c_lpc2k_handler(int irq, void *dev_id)
{
struct lpc2k_i2c *i2c = dev_id;
if (readl(i2c->base + LPC24XX_I2CONSET) & LPC24XX_SI) {
i2c_lpc2k_pump_msg(i2c);
return IRQ_HANDLED;
}
return IRQ_NONE;
}
static u32 i2c_lpc2k_functionality(struct i2c_adapter *adap)
{
/* Only emulated SMBus for now */
return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
}
static const struct i2c_algorithm i2c_lpc2k_algorithm = {
.master_xfer = i2c_lpc2k_xfer,
.functionality = i2c_lpc2k_functionality,
};
static int i2c_lpc2k_probe(struct platform_device *pdev)
{
struct lpc2k_i2c *i2c;
struct resource *res;
u32 bus_clk_rate;
u32 scl_high;
u32 clkrate;
int ret;
i2c = devm_kzalloc(&pdev->dev, sizeof(*i2c), GFP_KERNEL);
if (!i2c)
return -ENOMEM;
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
i2c->base = devm_ioremap_resource(&pdev->dev, res);
if (IS_ERR(i2c->base))
return PTR_ERR(i2c->base);
i2c->irq = platform_get_irq(pdev, 0);
if (i2c->irq < 0) {
dev_err(&pdev->dev, "can't get interrupt resource\n");
return i2c->irq;
}
init_waitqueue_head(&i2c->wait);
i2c->clk = devm_clk_get(&pdev->dev, NULL);
if (IS_ERR(i2c->clk)) {
dev_err(&pdev->dev, "error getting clock\n");
return PTR_ERR(i2c->clk);
}
ret = clk_prepare_enable(i2c->clk);
if (ret) {
dev_err(&pdev->dev, "unable to enable clock.\n");
return ret;
}
ret = devm_request_irq(&pdev->dev, i2c->irq, i2c_lpc2k_handler, 0,
dev_name(&pdev->dev), i2c);
if (ret < 0) {
dev_err(&pdev->dev, "can't request interrupt.\n");
goto fail_clk;
}
disable_irq_nosync(i2c->irq);
/* Place controller is a known state */
i2c_lpc2k_reset(i2c);
ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
&bus_clk_rate);
if (ret)
bus_clk_rate = 100000; /* 100 kHz default clock rate */
clkrate = clk_get_rate(i2c->clk);
if (clkrate == 0) {
dev_err(&pdev->dev, "can't get I2C base clock\n");
ret = -EINVAL;
goto fail_clk;
}
/* Setup I2C dividers to generate clock with proper duty cycle */
clkrate = clkrate / bus_clk_rate;
if (bus_clk_rate <= 100000)
scl_high = (clkrate * I2C_STD_MODE_DUTY) / 100;
else if (bus_clk_rate <= 400000)
scl_high = (clkrate * I2C_FAST_MODE_DUTY) / 100;
else
scl_high = (clkrate * I2C_FAST_MODE_PLUS_DUTY) / 100;
writel(scl_high, i2c->base + LPC24XX_I2SCLH);
writel(clkrate - scl_high, i2c->base + LPC24XX_I2SCLL);
platform_set_drvdata(pdev, i2c);
i2c_set_adapdata(&i2c->adap, i2c);
i2c->adap.owner = THIS_MODULE;
strlcpy(i2c->adap.name, "LPC2K I2C adapter", sizeof(i2c->adap.name));
i2c->adap.algo = &i2c_lpc2k_algorithm;
i2c->adap.dev.parent = &pdev->dev;
i2c->adap.dev.of_node = pdev->dev.of_node;
ret = i2c_add_adapter(&i2c->adap);
if (ret < 0) {
dev_err(&pdev->dev, "failed to add adapter!\n");
goto fail_clk;
}
dev_info(&pdev->dev, "LPC2K I2C adapter\n");
return 0;
fail_clk:
clk_disable_unprepare(i2c->clk);
return ret;
}
static int i2c_lpc2k_remove(struct platform_device *dev)
{
struct lpc2k_i2c *i2c = platform_get_drvdata(dev);
i2c_del_adapter(&i2c->adap);
clk_disable_unprepare(i2c->clk);
return 0;
}
#ifdef CONFIG_PM
static int i2c_lpc2k_suspend(struct device *dev)
{
struct platform_device *pdev = to_platform_device(dev);
struct lpc2k_i2c *i2c = platform_get_drvdata(pdev);
clk_disable(i2c->clk);
return 0;
}
static int i2c_lpc2k_resume(struct device *dev)
{
struct platform_device *pdev = to_platform_device(dev);
struct lpc2k_i2c *i2c = platform_get_drvdata(pdev);
clk_enable(i2c->clk);
i2c_lpc2k_reset(i2c);
return 0;
}
static const struct dev_pm_ops i2c_lpc2k_dev_pm_ops = {
.suspend_noirq = i2c_lpc2k_suspend,
.resume_noirq = i2c_lpc2k_resume,
};
#define I2C_LPC2K_DEV_PM_OPS (&i2c_lpc2k_dev_pm_ops)
#else
#define I2C_LPC2K_DEV_PM_OPS NULL
#endif
static const struct of_device_id lpc2k_i2c_match[] = {
{ .compatible = "nxp,lpc1788-i2c" },
{},
};
MODULE_DEVICE_TABLE(of, lpc2k_i2c_match);
static struct platform_driver i2c_lpc2k_driver = {
.probe = i2c_lpc2k_probe,
.remove = i2c_lpc2k_remove,
.driver = {
.name = "lpc2k-i2c",
.pm = I2C_LPC2K_DEV_PM_OPS,
.of_match_table = lpc2k_i2c_match,
},
};
module_platform_driver(i2c_lpc2k_driver);
MODULE_AUTHOR("Kevin Wells <kevin.wells@nxp.com>");
MODULE_DESCRIPTION("I2C driver for LPC2xxx devices");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:lpc2k-i2c");
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