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    Subject[PATCH V3 2/4] drivers/i2c/busses/i2c-at91.c: add new driver
    This driver has the following properties compared to the old driver:
    1. Support for multiple interfaces.
    2. Interrupt driven I/O as opposed to polling/busy waiting.
    3. Support for _one_ repeated start (Sr) condition, which is enough
    for most real-world applications including all SMBus transfer types.
    (The hardware does not support issuing arbitrary Sr conditions on the
    bus.)

    Tested on Atmel G45 with BQ20Z80 battery SMBus client.

    Signed-off-by: Nikolaus Voss <n.voss@weinmann.de>
    ---
    drivers/i2c/busses/Kconfig | 11 +-
    drivers/i2c/busses/i2c-at91.c | 442 +++++++++++++++++++++++++++++++++++++++++
    2 files changed, 446 insertions(+), 7 deletions(-)
    create mode 100644 drivers/i2c/busses/i2c-at91.c

    diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
    index 646068e..c4b6bdc 100644
    --- a/drivers/i2c/busses/Kconfig
    +++ b/drivers/i2c/busses/Kconfig
    @@ -286,18 +286,15 @@ comment "I2C system bus drivers (mostly embedded / system-on-chip)"

    config I2C_AT91
    tristate "Atmel AT91 I2C Two-Wire interface (TWI)"
    - depends on ARCH_AT91 && EXPERIMENTAL && BROKEN
    + depends on ARCH_AT91 && EXPERIMENTAL
    help
    This supports the use of the I2C interface on Atmel AT91
    processors.

    - This driver is BROKEN because the controller which it uses
    - will easily trigger RX overrun and TX underrun errors. Using
    - low I2C clock rates may partially work around those issues
    - on some systems. Another serious problem is that there is no
    - documented way to issue repeated START conditions, as needed
    + A serious problem is that there is no documented way to issue
    + repeated START conditions for more than two messages, as needed
    to support combined I2C messages. Use the i2c-gpio driver
    - unless your system can cope with those limitations.
    + unless your system can cope with this limitation.

    config I2C_AU1550
    tristate "Au1550/Au1200 SMBus interface"
    diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c
    new file mode 100644
    index 0000000..e35479b
    --- /dev/null
    +++ b/drivers/i2c/busses/i2c-at91.c
    @@ -0,0 +1,442 @@
    +/*
    +
    + i2c Support for Atmel's AT91 Two-Wire Interface (TWI)
    +
    + Copyright (C) 2011 Nikolaus Voss <n.voss@weinmann.de>
    +
    + Evolved from original work by:
    + Copyright (C) 2004 Rick Bronson
    + Converted to 2.6 by Andrew Victor <andrew@sanpeople.com>
    +
    + Borrowed heavily from original work by:
    + Copyright (C) 2000 Philip Edelbrock <phil@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/kernel.h>
    +#include <linux/err.h>
    +#include <linux/slab.h>
    +#include <linux/types.h>
    +#include <linux/i2c.h>
    +#include <linux/init.h>
    +#include <linux/interrupt.h>
    +#include <linux/clk.h>
    +#include <linux/platform_device.h>
    +#include <linux/io.h>
    +
    +#include <mach/at91_twi.h>
    +#include <mach/board.h>
    +#include <mach/cpu.h>
    +
    +#define TWI_CLOCK 100000 /* Hz. max 400 Kbits/sec */
    +#define AT91_I2C_TIMEOUT (HZ/100) /* transfer timeout */
    +
    +struct at91_twi_dev {
    + struct device *dev;
    + void __iomem *base;
    + struct completion cmd_complete;
    + struct clk *clk;
    + u8 *buf;
    + size_t buf_len;
    + int irq;
    + unsigned transfer_status;
    + struct i2c_adapter adapter;
    +};
    +
    +static inline unsigned at91_twi_read(struct at91_twi_dev *dev, unsigned reg)
    +{
    + return __raw_readl(dev->base + (reg));
    +}
    +
    +static inline void at91_twi_write(struct at91_twi_dev *dev, unsigned reg,
    + unsigned val)
    +{
    + __raw_writel((val), dev->base + (reg));
    +}
    +
    +static inline void at91_disable_twi_interrupts(struct at91_twi_dev *dev)
    +{
    + at91_twi_write(dev, AT91_TWI_IDR,
    + AT91_TWI_TXCOMP | AT91_TWI_RXRDY | AT91_TWI_TXRDY);
    +}
    +
    +static void at91_init_twi_bus(struct at91_twi_dev *dev)
    +{
    + at91_disable_twi_interrupts(dev);
    + at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_SWRST);
    + at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_MSEN);
    + at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_SVDIS);
    +}
    +
    +static void at91_set_twi_clock(struct at91_twi_dev *dev)
    +{
    + unsigned long cdiv, ckdiv;
    +
    + /* Calcuate clock dividers */
    + cdiv = (clk_get_rate(dev->clk) / (2 * TWI_CLOCK)) - 3;
    + cdiv = cdiv + 1; /* round up */
    + ckdiv = 0;
    + while (cdiv > 255) {
    + ckdiv++;
    + cdiv = cdiv >> 1;
    + }
    +
    + if (cpu_is_at91rm9200()) { /* AT91RM9200 Errata #22 */
    + if (ckdiv > 5) {
    + printk(KERN_ERR "AT91 I2C: Invalid TWI_CLOCK value!\n");
    + ckdiv = 5;
    + }
    + }
    +
    + at91_twi_write(dev, AT91_TWI_CWGR, (ckdiv << 16) | (cdiv << 8) | cdiv);
    +}
    +
    +static void __devinit at91_twi_hwinit(struct at91_twi_dev *dev)
    +{
    + at91_init_twi_bus(dev);
    + at91_set_twi_clock(dev);
    +}
    +
    +static void at91_twi_write_next_byte(struct at91_twi_dev *dev)
    +{
    + if (dev->buf_len > 0) {
    +
    + const u8 c = *(dev->buf++);
    +
    + at91_twi_write(dev, AT91_TWI_THR, c);
    +
    + /* send stop when last byte has been written */
    + if (--dev->buf_len == 0)
    + at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_STOP);
    +
    + dev_dbg(dev->dev, "wrote 0x%x, to go %d\n", c, dev->buf_len);
    + }
    +}
    +
    +static void at91_twi_read_next_byte(struct at91_twi_dev *dev)
    +{
    + const u8 c = at91_twi_read(dev, AT91_TWI_RHR) & 0xff;
    +
    + *(dev->buf)++ = c;
    +
    + /* send stop if second but last byte has been read */
    + if (--dev->buf_len == 1)
    + at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_STOP);
    +
    + dev_dbg(dev->dev, "read 0x%x, to go %d\n", c, dev->buf_len);
    +}
    +
    +static irqreturn_t atmel_twi_interrupt(int irq, void *dev_id)
    +{
    + struct at91_twi_dev *dev = dev_id;
    + const unsigned status = at91_twi_read(dev, AT91_TWI_SR);
    + const unsigned irqstatus = status & at91_twi_read(dev, AT91_TWI_IMR);
    +
    + if (irqstatus & AT91_TWI_TXCOMP) {
    + at91_disable_twi_interrupts(dev);
    + dev->transfer_status = status;
    + complete(&dev->cmd_complete);
    + }
    + else if (irqstatus & AT91_TWI_RXRDY) {
    + at91_twi_read_next_byte(dev);
    + }
    + else if (irqstatus & AT91_TWI_TXRDY) {
    + at91_twi_write_next_byte(dev);
    + }
    + else {
    + return IRQ_NONE;
    + }
    +
    + return IRQ_HANDLED;
    +}
    +
    +int at91_do_twi_transfer(struct at91_twi_dev *dev, bool is_read)
    +{
    + int ret = 0;
    +
    + INIT_COMPLETION(dev->cmd_complete);
    +
    + if (is_read) {
    + if (!dev->buf_len)
    + at91_twi_write(dev, AT91_TWI_CR,
    + AT91_TWI_START | AT91_TWI_STOP);
    + else
    + at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_START);
    +
    + at91_twi_write(dev, AT91_TWI_IER,
    + AT91_TWI_TXCOMP | AT91_TWI_RXRDY);
    +
    + } else {
    +
    + at91_twi_write_next_byte(dev);
    +
    + at91_twi_write(dev, AT91_TWI_IER,
    + AT91_TWI_TXCOMP | AT91_TWI_TXRDY);
    + }
    +
    + ret = wait_for_completion_interruptible_timeout(&dev->cmd_complete,
    + dev->adapter.timeout);
    + if (ret == 0) {
    + dev_err(dev->dev, "controller timed out\n");
    + at91_init_twi_bus(dev);
    + return -ETIMEDOUT;
    + }
    +
    + if (dev->transfer_status & AT91_TWI_NACK) {
    + dev_dbg(dev->dev, "received nack\n");
    + return -ENODEV;
    + }
    +
    + if (dev->transfer_status & AT91_TWI_OVRE) {
    + dev_err(dev->dev, "overrun while reading\n");
    + return -EIO;
    + }
    +
    + dev_dbg(dev->dev, "transfer complete\n");
    +
    + return 0;
    +}
    +
    +static int at91_twi_xfer(struct i2c_adapter *adap, struct i2c_msg *msg, int num)
    +{
    + struct at91_twi_dev *dev = i2c_get_adapdata(adap);
    + int ret;
    + unsigned int_addr_flag = 0;
    + struct i2c_msg *m_start = msg;
    +
    + dev_dbg(&adap->dev, "at91_xfer: processing %d messages:\n", num);
    +
    + /* the hardware can handle at most two messages concatenated by a
    + * repeated start via it's internal address feature.
    + */
    + if (num > 2) {
    + dev_err(dev->dev,
    + "cannot handle more than two concatenated messages.\n");
    + return 0;
    +
    + } else if (num == 2) {
    +
    + int internal_address = 0;
    + int i;
    +
    + if (msg->flags & I2C_M_RD) {
    + dev_err(dev->dev, "first transfer must be write.\n");
    + return 0;
    + }
    +
    + if (msg->len > 3) {
    + dev_err(dev->dev, "first message size must be <= 3.\n");
    + return 0;
    + }
    +
    + /* 1st msg is put into the internal address, start with 2nd */
    + m_start = &msg[1];
    +
    + for (i = 0; i < msg->len; ++i) {
    + internal_address |= ((unsigned)msg->buf[i]) << (8 * i);
    + int_addr_flag += AT91_TWI_IADRSZ_1;
    + }
    +
    + at91_twi_write(dev, AT91_TWI_IADR, internal_address);
    + }
    +
    + at91_twi_write(dev, AT91_TWI_MMR, (m_start->addr << 16) | int_addr_flag
    + | ((m_start->flags & I2C_M_RD) ? AT91_TWI_MREAD : 0));
    +
    + dev->buf_len = m_start->len;
    + dev->buf = m_start->buf;
    +
    + ret = at91_do_twi_transfer(dev, m_start->flags & I2C_M_RD);
    +
    + if (ret < 0)
    + return ret;
    +
    + return num;
    +}
    +
    +static u32 at91_twi_func(struct i2c_adapter *adapter)
    +{
    + return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
    +}
    +
    +static struct i2c_algorithm at91_twi_algorithm = {
    + .master_xfer = at91_twi_xfer,
    + .functionality = at91_twi_func,
    +};
    +
    +static int __devinit at91_twi_probe(struct platform_device *pdev)
    +{
    + struct at91_twi_dev *dev;
    + struct resource *mem, *irq, *ioarea;
    + int rc;
    +
    + mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    + if (!mem)
    + return -ENODEV;
    +
    + irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
    + if (!irq)
    + return -ENODEV;
    +
    + ioarea = request_mem_region(mem->start, resource_size(mem), pdev->name);
    + if (!ioarea)
    + return -EBUSY;
    +
    + dev = kzalloc(sizeof(struct at91_twi_dev), GFP_KERNEL);
    + if (!dev) {
    + rc = -ENOMEM;
    + goto err_release_region;
    + }
    +
    + init_completion(&dev->cmd_complete);
    +
    + dev->dev = get_device(&pdev->dev);
    + dev->irq = irq->start;
    + platform_set_drvdata(pdev, dev);
    +
    + dev->clk = clk_get(&pdev->dev, "twi_clk");
    + if (IS_ERR(dev->clk)) {
    + dev_err(&pdev->dev, "no clock defined\n");
    + rc = -ENODEV;
    + goto err_free_mem;
    + }
    + clk_enable(dev->clk);
    +
    + dev->base = ioremap(mem->start, resource_size(mem));
    + if (!dev->base) {
    + rc = -EBUSY;
    + goto err_mem_ioremap;
    + }
    +
    + at91_twi_hwinit(dev);
    +
    + rc = request_irq(dev->irq, atmel_twi_interrupt, 0,
    + dev_name(&pdev->dev), dev);
    + if (rc) {
    + dev_err(&pdev->dev, "Cannot get irq %d: %d\n", dev->irq, rc);
    + goto err_unuse_clocks;
    + }
    +
    + snprintf(dev->adapter.name, sizeof(dev->adapter.name), "AT91");
    + i2c_set_adapdata(&dev->adapter, dev);
    + dev->adapter.owner = THIS_MODULE;
    + dev->adapter.class = I2C_CLASS_HWMON;
    + dev->adapter.algo = &at91_twi_algorithm;
    + dev->adapter.dev.parent = &pdev->dev;
    + dev->adapter.nr = pdev->id;
    + dev->adapter.timeout = AT91_I2C_TIMEOUT;
    +
    + rc = i2c_add_numbered_adapter(&dev->adapter);
    + if (rc) {
    + dev_err(&pdev->dev, "Adapter %s registration failed\n",
    + dev->adapter.name);
    + goto err_free_irq;
    + }
    +
    + dev_info(&pdev->dev, "AT91 i2c bus driver.\n");
    + return 0;
    +
    +err_free_irq:
    + free_irq(dev->irq, dev);
    +err_unuse_clocks:
    + iounmap(dev->base);
    +err_mem_ioremap:
    + clk_disable(dev->clk);
    + clk_put(dev->clk);
    + dev->clk = NULL;
    +err_free_mem:
    + platform_set_drvdata(pdev, NULL);
    + put_device(&pdev->dev);
    + kfree(dev);
    +err_release_region:
    + release_mem_region(mem->start, resource_size(mem));
    +
    + return rc;
    +}
    +
    +static int __devexit at91_twi_remove(struct platform_device *pdev)
    +{
    + struct at91_twi_dev *dev = platform_get_drvdata(pdev);
    + struct resource *mem;
    + int rc;
    +
    + platform_set_drvdata(pdev, NULL);
    + rc = i2c_del_adapter(&dev->adapter);
    + put_device(&pdev->dev);
    +
    + clk_disable(dev->clk);
    + clk_put(dev->clk);
    + dev->clk = NULL;
    +
    + free_irq(dev->irq, dev);
    +
    + iounmap(dev->base);
    + kfree(dev);
    +
    + mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    + release_mem_region(mem->start, resource_size(mem));
    +
    + return rc;
    +}
    +
    +#ifdef CONFIG_PM
    +
    +static int at91_twi_suspend(struct device *dev)
    +{
    + struct at91_twi_dev *twi_dev = dev_get_drvdata(dev);
    +
    + clk_disable(twi_dev->clk);
    +
    + return 0;
    +}
    +
    +static int at91_twi_resume(struct device *dev)
    +{
    + struct at91_twi_dev *twi_dev = dev_get_drvdata(dev);
    +
    + return clk_enable(twi_dev->clk);
    +}
    +
    +static const struct dev_pm_ops at91_twi_pm = {
    + .suspend = at91_twi_suspend,
    + .resume = at91_twi_resume,
    +};
    +
    +#define at91_twi_pm_ops (&at91_twi_pm)
    +#else
    +#define at91_twi_pm_ops NULL
    +#endif
    +
    +MODULE_ALIAS("platform:at91_i2c");
    +
    +static struct platform_driver at91_twi_driver = {
    + .probe = at91_twi_probe,
    + .remove = __devexit_p(at91_twi_remove),
    + .driver = {
    + .name = "at91_i2c",
    + .owner = THIS_MODULE,
    + .pm = at91_twi_pm_ops,
    + },
    +};
    +
    +static int __init at91_twi_init(void)
    +{
    + return platform_driver_register(&at91_twi_driver);
    +}
    +
    +static void __exit at91_twi_exit(void)
    +{
    + platform_driver_unregister(&at91_twi_driver);
    +}
    +
    +module_init(at91_twi_init);
    +module_exit(at91_twi_exit);
    +
    +MODULE_AUTHOR("Nikolaus Voss");
    +MODULE_DESCRIPTION("I2C (TWI) driver for Atmel AT91");
    +MODULE_LICENSE("GPL");
    --
    1.7.5.4


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