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: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Wolfram Sang <wolfram@the-dreams.de>

3 files changed, 355 insertions, 0 deletions

diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index 74e18bc0bf62..8cbd9cd1e0fa 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -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
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 23c9d55bc880..8f4fc23b85b1 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -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
diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c
new file mode 100644
index 000000000000..ea4b08fc3353
--- /dev/null
+++ b/drivers/i2c/busses/i2c-bcm2835.c
@@ -0,0 +1,342 @@
+/*
+ * 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");