i2c: bcm2835: Add support for dynamic clock

Support a dynamic clock by reading the frequency and setting the
divisor in the transfer function instead of during probe.

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Reviewed-by: Martin Sperl <kernel@martin.sperl.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

diff --git a/drivers/i2c/busses/i2c-bcm2835.c b/drivers/i2c/busses/i2c-bcm2835.c
index d2085dd3742eabebc537621968088261f8dc7ea8..c3436f627028477f7e21b47e079fd5ab06ec188a 100644 (file)
--- a/drivers/i2c/busses/i2c-bcm2835.c
+++ b/drivers/i2c/busses/i2c-bcm2835.c
@@ -58,6 +58,7 @@ struct bcm2835_i2c_dev {
        void __iomem *regs;
        struct clk *clk;
        int irq;
+       u32 bus_clk_rate;
        struct i2c_adapter adapter;
        struct completion completion;
        struct i2c_msg *curr_msg;
@@ -78,6 +79,30 @@ static inline u32 bcm2835_i2c_readl(struct bcm2835_i2c_dev *i2c_dev, u32 reg)
        return readl(i2c_dev->regs + reg);
 }
 
+static int bcm2835_i2c_set_divider(struct bcm2835_i2c_dev *i2c_dev)
+{
+       u32 divider;
+
+       divider = DIV_ROUND_UP(clk_get_rate(i2c_dev->clk),
+                              i2c_dev->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++;
+       if ((divider < BCM2835_I2C_CDIV_MIN) ||
+           (divider > BCM2835_I2C_CDIV_MAX)) {
+               dev_err_ratelimited(i2c_dev->dev, "Invalid clock-frequency\n");
+               return -EINVAL;
+       }
+
+       bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DIV, divider);
+
+       return 0;
+}
+
 static void bcm2835_fill_txfifo(struct bcm2835_i2c_dev *i2c_dev)
 {
        u32 val;
@@ -224,7 +249,7 @@ static int bcm2835_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
 {
        struct bcm2835_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
        unsigned long time_left;
-       int i;
+       int i, ret;
 
        for (i = 0; i < (num - 1); i++)
                if (msgs[i].flags & I2C_M_RD) {
@@ -233,6 +258,10 @@ static int bcm2835_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
                        return -EOPNOTSUPP;
                }
 
+       ret = bcm2835_i2c_set_divider(i2c_dev);
+       if (ret)
+               return ret;
+
        i2c_dev->curr_msg = msgs;
        i2c_dev->num_msgs = num;
        reinit_completion(&i2c_dev->completion);
@@ -282,7 +311,6 @@ static int bcm2835_i2c_probe(struct platform_device *pdev)
 {
        struct bcm2835_i2c_dev *i2c_dev;
        struct resource *mem, *irq;
-       u32 bus_clk_rate, divider;
        int ret;
        struct i2c_adapter *adap;
 
@@ -306,27 +334,12 @@ static int bcm2835_i2c_probe(struct platform_device *pdev)
        }
 
        ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
-                                  &bus_clk_rate);
+                                  &i2c_dev->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++;
-       if ((divider < BCM2835_I2C_CDIV_MIN) ||
-           (divider > BCM2835_I2C_CDIV_MAX)) {
-               dev_err(&pdev->dev, "Invalid clock-frequency\n");
-               return -ENODEV;
+               i2c_dev->bus_clk_rate = 100000;
        }
-       bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DIV, divider);
 
        irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
        if (!irq) {