[PATCH V3 2/4] drivers/i2c/busses/i2c-at91.c: add new driver

Nikolaus Voss
2011-11-08T14:15:52Z

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