i2c: ocores: add common clock support

Allow bus clock specification as a common clock handle. This makes this
controller easier to use in a setup based on common clock framework.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Documentation/devicetree/bindings/i2c/i2c-ocores.txt

@@ -4,8 +4,10 @@ Required properties:
 - compatible      : "opencores,i2c-ocores" or "aeroflexgaisler,i2cmst"
 - reg             : bus address start and address range size of device
 - interrupts      : interrupt number
+- clocks          : handle to the controller clock; see the note below.
+                    Mutually exclusive with opencores,ip-clock-frequency
 - opencores,ip-clock-frequency: frequency of the controller clock in Hz;
-                    see the note below
+                    see the note below. Mutually exclusive with clocks
 - #address-cells  : should be <1>
 - #size-cells     : should be <0>
 
@@ -20,14 +22,16 @@ Note
 clock-frequency property is meant to control the bus frequency for i2c bus
 drivers, but it was incorrectly used to specify i2c controller input clock
 frequency. So the following rules are set to fix this situation:
-- if clock-frequency is present and opencores,ip-clock-frequency is not,
-  then clock-frequency specifies i2c controller clock frequency. This is
-  to keep backwards compatibility with setups using old DTB. i2c bus
+- if clock-frequency is present and neither opencores,ip-clock-frequency nor
+  clocks are, then clock-frequency specifies i2c controller clock frequency.
+  This is to keep backwards compatibility with setups using old DTB. i2c bus
   frequency is fixed at 100 KHz.
+- if clocks is present it specifies i2c controller clock. clock-frequency
+  property specifies i2c bus frequency.
 - if opencores,ip-clock-frequency is present it specifies i2c controller
   clock frequency. clock-frequency property specifies i2c bus frequency.
 
-Example:
+Examples:
 
 	i2c0: ocores@a0000000 {
 		#address-cells = <1>;
@@ -40,6 +44,24 @@ Example:
 		reg-shift = <0>;	/* 8 bit registers */
 		reg-io-width = <1>;	/* 8 bit read/write */
 
+		dummy@60 {
+			compatible = "dummy";
+			reg = <0x60>;
+		};
+	};
+or
+	i2c0: ocores@a0000000 {
+		#address-cells = <1>;
+		#size-cells = <0>;
+		compatible = "opencores,i2c-ocores";
+		reg = <0xa0000000 0x8>;
+		interrupts = <10>;
+		clocks = <&osc>;
+		clock-frequency = <400000>; /* i2c bus frequency 400 KHz */
+
+		reg-shift = <0>;	/* 8 bit registers */
+		reg-io-width = <1>;	/* 8 bit read/write */
+
 		dummy@60 {
 			compatible = "dummy";
 			reg = <0x60>;

drivers/i2c/busses/i2c-ocores.c

@@ -12,6 +12,7 @@
  * kind, whether express or implied.
  */
 
+#include <linux/clk.h>
 #include <linux/err.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
@@ -35,6 +36,7 @@ struct ocores_i2c {
 	int pos;
 	int nmsgs;
 	int state; /* see STATE_ */
+	struct clk *clk;
 	int ip_clock_khz;
 	int bus_clock_khz;
 	void (*setreg)(struct ocores_i2c *i2c, int reg, u8 value);
@@ -339,7 +341,21 @@ static int ocores_i2c_of_probe(struct platform_device *pdev,
 							&clock_frequency);
 	i2c->bus_clock_khz = 100;
 
-	if (of_property_read_u32(np, "opencores,ip-clock-frequency", &val)) {
+	i2c->clk = devm_clk_get(&pdev->dev, NULL);
+
+	if (!IS_ERR(i2c->clk)) {
+		int ret = clk_prepare_enable(i2c->clk);
+
+		if (ret) {
+			dev_err(&pdev->dev,
+				"clk_prepare_enable failed: %d\n", ret);
+			return ret;
+		}
+		i2c->ip_clock_khz = clk_get_rate(i2c->clk) / 1000;
+		if (clock_frequency_present)
+			i2c->bus_clock_khz = clock_frequency / 1000;
+	} else if (of_property_read_u32(np, "opencores,ip-clock-frequency",
+					&val)) {
 		if (!clock_frequency_present) {
 			dev_err(&pdev->dev,
 				"Missing required parameter 'opencores,ip-clock-frequency'\n");
@@ -477,6 +493,9 @@ static int ocores_i2c_remove(struct platform_device *pdev)
 	/* remove adapter & data */
 	i2c_del_adapter(&i2c->adap);
 
+	if (!IS_ERR(i2c->clk))
+		clk_disable_unprepare(i2c->clk);
+
 	return 0;
 }
 
@@ -489,6 +508,8 @@ static int ocores_i2c_suspend(struct device *dev)
 	/* make sure the device is disabled */
 	oc_setreg(i2c, OCI2C_CONTROL, ctrl & ~(OCI2C_CTRL_EN|OCI2C_CTRL_IEN));
 
+	if (!IS_ERR(i2c->clk))
+		clk_disable_unprepare(i2c->clk);
 	return 0;
 }
 
@@ -496,6 +517,16 @@ static int ocores_i2c_resume(struct device *dev)
 {
 	struct ocores_i2c *i2c = dev_get_drvdata(dev);
 
+	if (!IS_ERR(i2c->clk)) {
+		int ret = clk_prepare_enable(i2c->clk);
+
+		if (ret) {
+			dev_err(dev,
+				"clk_prepare_enable failed: %d\n", ret);
+			return ret;
+		}
+		i2c->ip_clock_khz = clk_get_rate(i2c->clk) / 1000;
+	}
 	return ocores_init(dev, i2c);
 }