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Subject[PATCH v9 3/4] 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.)

testing: SoC: at91sam9g45
- BQ20Z80 battery SMBus client.
- on a 2.6.38 kernel with several i2c clients (temp-sensor,
audio-codec, touchscreen-controller, w1-bridge, io-expanders)

Signed-off-by: Nikolaus Voss <n.voss@weinmann.de>
Reviewed-by: Felipe Balbi <balbi@ti.com>
Tested-by: Hubert Feurstein <h.feurstein@gmail.com>

---
arch/arm/mach-at91/at91rm9200_devices.c | 9 +
drivers/i2c/busses/Kconfig | 11 +-
drivers/i2c/busses/Makefile | 1 +
drivers/i2c/busses/i2c-at91.c | 455 +++++++++++++++++++++++++++++++
4 files changed, 469 insertions(+), 7 deletions(-)
create mode 100644 drivers/i2c/busses/i2c-at91.c
diff --git a/arch/arm/mach-at91/at91rm9200_devices.c b/arch/arm/mach-at91/at91rm9200_devices.c
index 97676bd..0912f29 100644
--- a/arch/arm/mach-at91/at91rm9200_devices.c
+++ b/arch/arm/mach-at91/at91rm9200_devices.c
@@ -493,9 +493,18 @@ static struct resource twi_resources[] = {
},
};

+static const struct platform_device_id twi_id = {
+ /*
+ * driver_data is "1" for hardware with ckdiv upper limit == 5
+ * (AT91RM9200 erratum 22), "0" for twi modules without this bug
+ */
+ .driver_data = 1,
+};
+
static struct platform_device at91rm9200_twi_device = {
.name = "at91_i2c",
.id = -1,
+ .id_entry = &twi_id,
.resource = twi_resources,
.num_resources = ARRAY_SIZE(twi_resources),
};
diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index 3101dd5..92158df 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -285,18 +285,15 @@ 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/Au1300 SMBus interface"
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index e8a1852..fba6da6 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -28,6 +28,7 @@ obj-$(CONFIG_I2C_HYDRA) += i2c-hydra.o
obj-$(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-$(CONFIG_I2C_BLACKFIN_TWI) += i2c-bfin-twi.o
obj-$(CONFIG_I2C_CPM) += i2c-cpm.o
diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c
new file mode 100644
index 0000000..40c39a2
--- /dev/null
+++ b/drivers/i2c/busses/i2c-at91.c
@@ -0,0 +1,455 @@
+/*
+ * i2c Support for Atmel's AT91 Two-Wire Interface (TWI)
+ *
+ * Copyright (C) 2011 Weinmann Medical GmbH
+ * Author: 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/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 TWI_CLK_HZ 100000 /* max 400 Kbits/s */
+#define AT91_I2C_TIMEOUT msecs_to_jiffies(100) /* transfer timeout */
+
+/* AT91 TWI register definitions */
+#define AT91_TWI_CR 0x0000 /* Control Register */
+#define AT91_TWI_START 0x0001 /* Send a Start Condition */
+#define AT91_TWI_STOP 0x0002 /* Send a Stop Condition */
+#define AT91_TWI_MSEN 0x0004 /* Master Transfer Enable */
+#define AT91_TWI_SVDIS 0x0020 /* Slave Transfer Disable */
+#define AT91_TWI_SWRST 0x0080 /* Software Reset */
+
+#define AT91_TWI_MMR 0x0004 /* Master Mode Register */
+#define AT91_TWI_IADRSZ_1 0x0100 /* Internal Device Address Size */
+#define AT91_TWI_MREAD 0x1000 /* Master Read Direction */
+
+#define AT91_TWI_IADR 0x000c /* Internal Address Register */
+
+#define AT91_TWI_CWGR 0x0010 /* Clock Waveform Generator Reg */
+
+#define AT91_TWI_SR 0x0020 /* Status Register */
+#define AT91_TWI_TXCOMP 0x0001 /* Transmission Complete */
+#define AT91_TWI_RXRDY 0x0002 /* Receive Holding Register Ready */
+#define AT91_TWI_TXRDY 0x0004 /* Transmit Holding Register Ready */
+
+#define AT91_TWI_OVRE 0x0040 /* Overrun Error */
+#define AT91_TWI_UNRE 0x0080 /* Underrun Error */
+#define AT91_TWI_NACK 0x0100 /* Not Acknowledged */
+
+#define AT91_TWI_IER 0x0024 /* Interrupt Enable Register */
+#define AT91_TWI_IDR 0x0028 /* Interrupt Disable Register */
+#define AT91_TWI_IMR 0x002c /* Interrupt Mask Register */
+#define AT91_TWI_RHR 0x0030 /* Receive Holding Register */
+#define AT91_TWI_THR 0x0034 /* Transmit Holding Register */
+
+struct at91_twi_dev {
+ struct device *dev;
+ void __iomem *base;
+ struct completion cmd_complete;
+ struct clk *clk;
+ u8 *buf;
+ size_t buf_len;
+ struct i2c_msg *msg;
+ int irq;
+ unsigned transfer_status;
+ struct i2c_adapter adapter;
+ bool has_ckdiv_limit_bug;
+ unsigned twi_cwgr_reg;
+};
+
+static unsigned at91_twi_read(struct at91_twi_dev *dev, unsigned reg)
+{
+ return readl_relaxed(dev->base + reg);
+}
+
+static void at91_twi_write(struct at91_twi_dev *dev, unsigned reg, unsigned val)
+{
+ writel_relaxed(val, dev->base + reg);
+}
+
+static 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);
+ at91_twi_write(dev, AT91_TWI_CWGR, dev->twi_cwgr_reg);
+}
+
+/*
+ * Calculate symmetric clock as stated in datasheet:
+ * twi_clk = F_MAIN / (2 * cdiv * (1 << ckdiv) + 4)
+ */
+static void __devinit at91_calc_twi_clock(struct at91_twi_dev *dev, int twi_clk)
+{
+ const int div = DIV_ROUND_UP(clk_get_rate(dev->clk), 2 * twi_clk) - 2;
+ int ckdiv = fls(div >> 8);
+ const int cdiv = div >> ckdiv;
+
+ if (dev->has_ckdiv_limit_bug && (ckdiv > 5)) {
+ dev_warn(dev->dev, "AT91RM9200 erratum 22: using ckdiv = 5.\n");
+ ckdiv = 5;
+ }
+
+ dev->twi_cwgr_reg = (ckdiv << 16) | (cdiv << 8) | cdiv;
+}
+
+static void at91_twi_write_next_byte(struct at91_twi_dev *dev)
+{
+ if (dev->buf_len <= 0)
+ return;
+
+ at91_twi_write(dev, AT91_TWI_THR, *dev->buf);
+
+ /* 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", *dev->buf, dev->buf_len);
+
+ ++dev->buf;
+}
+
+static void at91_twi_read_next_byte(struct at91_twi_dev *dev)
+{
+ *dev->buf = at91_twi_read(dev, AT91_TWI_RHR) & 0xff;
+ --dev->buf_len;
+
+ /* handle I2C_SMBUS_BLOCK_DATA */
+ if (unlikely(dev->msg->flags & I2C_M_RECV_LEN)) {
+ dev->msg->flags &= ~I2C_M_RECV_LEN;
+ dev->buf_len += *dev->buf;
+ dev->msg->len = dev->buf_len + 1;
+ dev_dbg(dev->dev, "received block length %d\n", dev->buf_len);
+ }
+
+ /* 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", *dev->buf, dev->buf_len);
+
+ ++dev->buf;
+}
+
+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;
+}
+
+static int at91_do_twi_transfer(struct at91_twi_dev *dev)
+{
+ int ret;
+
+ dev_dbg(dev->dev, "transfer: %s %d bytes.\n",
+ (dev->msg->flags & I2C_M_RD) ? "read" : "write", dev->buf_len);
+
+ INIT_COMPLETION(dev->cmd_complete);
+ if (dev->msg->flags & I2C_M_RD) {
+ unsigned start_flags = AT91_TWI_START;
+
+ /* if only one byte is to be read, immediately stop transfer */
+ if (dev->buf_len <= 1 && !(dev->msg->flags & I2C_M_RECV_LEN))
+ start_flags |= AT91_TWI_STOP;
+ at91_twi_write(dev, AT91_TWI_CR, start_flags);
+ 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 -EREMOTEIO;
+ }
+ 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 -EINVAL;
+ }
+ if (msg->len > 3) {
+ dev_err(dev->dev, "first message size must be <= 3.\n");
+ return -EINVAL;
+ }
+
+ /* 1st msg is put into the internal address, start with 2nd */
+ m_start = &msg[1];
+ for (i = 0; i < msg->len; ++i) {
+ const unsigned addr = msg->buf[msg->len - 1 - i];
+
+ internal_address |= addr << (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;
+ dev->msg = m_start;
+
+ ret = at91_do_twi_transfer(dev);
+
+ return (ret < 0) ? ret : num;
+}
+
+static u32 at91_twi_func(struct i2c_adapter *adapter)
+{
+ return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL
+ | I2C_FUNC_SMBUS_READ_BLOCK_DATA;
+}
+
+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, *ioarea;
+ int irq, rc;
+
+ mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ if (!mem)
+ return -ENODEV;
+
+ irq = platform_get_irq(pdev, 0);
+ if (irq < 0)
+ return irq;
+
+ ioarea = request_mem_region(mem->start, resource_size(mem), pdev->name);
+ if (!ioarea)
+ return -EBUSY;
+
+ dev = kzalloc(sizeof(*dev), GFP_KERNEL);
+ if (!dev) {
+ rc = -ENOMEM;
+ goto err_release_region;
+ }
+
+ if (pdev->id_entry && pdev->id_entry->driver_data == 1)
+ dev->has_ckdiv_limit_bug = 1;
+
+ init_completion(&dev->cmd_complete);
+
+ dev->dev = &pdev->dev;
+ dev->irq = irq;
+ platform_set_drvdata(pdev, dev);
+
+ dev->clk = clk_get(dev->dev, NULL);
+ if (IS_ERR(dev->clk)) {
+ dev_err(dev->dev, "no clock defined\n");
+ rc = -ENODEV;
+ goto err_free_mem;
+ }
+ clk_prepare(dev->clk);
+ clk_enable(dev->clk);
+
+ dev->base = ioremap(mem->start, resource_size(mem));
+ if (!dev->base) {
+ rc = -EBUSY;
+ goto err_mem_ioremap;
+ }
+
+ at91_calc_twi_clock(dev, TWI_CLK_HZ);
+ at91_init_twi_bus(dev);
+
+ rc = request_irq(dev->irq, atmel_twi_interrupt, 0,
+ dev_name(dev->dev), dev);
+ if (rc) {
+ dev_err(dev->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 = dev->dev;
+ dev->adapter.nr = pdev->id;
+ dev->adapter.timeout = AT91_I2C_TIMEOUT;
+
+ rc = i2c_add_numbered_adapter(&dev->adapter);
+ if (rc) {
+ dev_err(dev->dev, "Adapter %s registration failed\n",
+ dev->adapter.name);
+ goto err_free_irq;
+ }
+
+ dev_info(dev->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_unprepare(dev->clk);
+ clk_put(dev->clk);
+err_free_mem:
+ 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;
+
+ rc = i2c_del_adapter(&dev->adapter);
+ clk_disable(dev->clk);
+ clk_unprepare(dev->clk);
+ clk_put(dev->clk);
+ 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_runtime_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_runtime_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 = {
+ .runtime_suspend = at91_twi_runtime_suspend,
+ .runtime_resume = at91_twi_runtime_resume,
+};
+
+#define at91_twi_pm_ops (&at91_twi_pm)
+#else
+#define at91_twi_pm_ops NULL
+#endif
+
+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);
+}
+
+subsys_initcall(at91_twi_init);
+module_exit(at91_twi_exit);
+
+MODULE_AUTHOR("Nikolaus Voss <n.voss@weinmann.de>");
+MODULE_DESCRIPTION("I2C (TWI) driver for Atmel AT91");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:at91_i2c");
--
1.7.5.4


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