[U-Boot] [RFC PATCH 4/6] clk: add device tree support for clock framework

[Masahiro Yamada <yamada.masahiro@socionext.com>]

Add device tree binding support for the clock uclass.  This allows
clock consumers to get the peripheral ID based on the "clocks"
property in the device tree.

Usage:
Assume the following device tree:

  clk: myclock {
          compatible = "myclocktype";
          #clock-cells = <1>;
  };

  uart {
          compatible = "myuart";
          clocks = <&clk 3>;
  };

  i2c {
          compatible = "myi2c";
          clocks = <&clk 5>;
  };

The UART, I2C driver can get the peripheral ID 3, 5, respectively
by calling fdt_clk_get().  The clock provider should set its get_id
callback to clk_get_id_simple.  This should be enough for most cases
although more complicated DT-PeripheralID translation would be
possible by a specific get_id callback.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---

 drivers/clk/Makefile  |  1 +
 drivers/clk/clk-fdt.c | 37 +++++++++++++++++++++++++++++++++++++
 include/clk.h         | 20 ++++++++++++++++++++
 3 files changed, 58 insertions(+)
 create mode 100644 drivers/clk/clk-fdt.c

diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index 4a6a4a8..5fcdf39 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -6,6 +6,7 @@
 #
 
 obj-$(CONFIG_CLK) += clk-uclass.o
+obj-$(CONFIG_$(SPL_)OF_CONTROL) += clk-fdt.o
 obj-$(CONFIG_ROCKCHIP_RK3036) += clk_rk3036.o
 obj-$(CONFIG_ROCKCHIP_RK3288) += clk_rk3288.o
 obj-$(CONFIG_SANDBOX) += clk_sandbox.o
diff --git a/drivers/clk/clk-fdt.c b/drivers/clk/clk-fdt.c
new file mode 100644
index 0000000..fc53157
--- /dev/null
+++ b/drivers/clk/clk-fdt.c
@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2015 Masahiro Yamada <yamada.masahiro@socionext.com>
+ *
+ * Device Tree support for clk uclass
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <clk.h>
+#include <dm/uclass.h>
+#include <fdtdec.h>
+
+int fdt_clk_get(const void *fdt, int nodeoffset, int index,
+		struct udevice **dev)
+{
+	struct fdtdec_phandle_args clkspec;
+	struct udevice *clkdev;
+	int rc;
+
+	rc = fdtdec_parse_phandle_with_args(fdt, nodeoffset, "clocks",
+					    "#clock-cells", 0, index, &clkspec);
+	if (rc)
+		return rc;
+
+	rc = uclass_get_device_by_of_offset(UCLASS_CLK, clkspec.node, &clkdev);
+	if (rc)
+		return rc;
+
+	rc = clk_get_id(clkdev, clkspec.args_count, clkspec.args);
+	if (rc < 0)
+		return rc;
+
+	if (dev)
+		*dev = clkdev;
+
+	return rc;
+}
diff --git a/include/clk.h b/include/clk.h
index 1efbaf2..518cb47 100644
--- a/include/clk.h
+++ b/include/clk.h
@@ -121,4 +121,24 @@ static inline int clk_get_id_simple(struct udevice *dev, int args_count,
 	return args_count > 0 ? args[0] : 0;
 }
 
+#if CONFIG_IS_ENABLED(OF_CONTROL)
+/**
+ * fdt_clk_get() - Get peripheral ID from device tree
+ *
+ * @fdt:	FDT blob
+ * @periph:	Offset of clock consumer node
+ * @index:	index of a phandle to parse out in "clocks" property
+ * @dev:	if not NULL, filled with pointer of clock provider
+ * @return peripheral ID, or -ve error code
+ */
+int fdt_clk_get(const void *fdt, int nodeoffset, int index,
+		struct udevice **dev);
+#else
+static inline int fdt_clk_get(const void *fdt, int nodeoffset, int index,
+			      struct udevice **dev);
+{
+	return -ENOSYS;
+}
+#endif
+
 #endif /* _CLK_H_ */
-- 
1.9.1