[PATCH v3 15/27] clk: ti: am335x: add clock manager driver

[Dario Binacchi <dariobin@libero.it>]

The implementation of this driver was needed to bind the sub-nodes of
the 'clocks' node. In fact, the lack of the compatible property in
the 'clocks' node does not allow the generic 'simple-bus' driver to bind
the 'clocks' node and in turn its sub-nodes.
The 'prcm at 200000' node is therefore the node closest to the 'clocks'
node whose driver can bind all the 'clocks' sub-nodes. In this way, the
address translation functions are able to walk along the device tree
towards the upper nodes until the address composition is completed.

prcm: prcm at 200000 {
	compatible = "ti,am3-prcm", "simple-bus";
	reg = <0x200000 0x4000>;
	#address-cells = <1>;
	#size-cells = <1>;
	ranges = <0 0x200000 0x4000>;

	prcm_clocks: clocks {
		#address-cells = <1>;
		#size-cells = <0>;
	};

	prcm_clockdomains: clockdomains {
	};
};

&prcm_clocks {
	...
	dpll_core_ck: dpll_core_ck at 490 {
        	#clock-cells = <0>;
		compatible = "ti,am3-dpll-core-clock";
		clocks = <&sys_clkin_ck>, <&sys_clkin_ck>;
		reg = <0x0490>, <0x045c>, <0x0468>;
	};
	...
};

For DT binding details see Linux doc:
- Documentation/devicetree/bindings/arm/omap/prcm.txt

Signed-off-by: Dario Binacchi <dariobin@libero.it>

---

Changes in v3:
- Add to commit message the references to linux kernel dt binding
  documentation.

Changes in v2:
- Remove the 'ti_am3_prcm_clocks' driver. Handle 'prcm_clocks' node in
  the 'ti_am3_prcm' driver.
- Update the commit message.

 drivers/clk/ti/Makefile   |  8 ++++-
 drivers/clk/ti/am3-prcm.c | 65 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 72 insertions(+), 1 deletion(-)
 create mode 100644 drivers/clk/ti/am3-prcm.c

diff --git a/drivers/clk/ti/Makefile b/drivers/clk/ti/Makefile
index 0b7e61cdf7..3d6e0cd79d 100644
--- a/drivers/clk/ti/Makefile
+++ b/drivers/clk/ti/Makefile
@@ -3,7 +3,13 @@
 # Copyright (C) 2020 Dario Binacchi <dariobin@libero.it>
 #
 
-obj-$(CONFIG_ARCH_OMAP2PLUS) += clk.o omap4-cm.o
+ifeq ($(CONFIG_ARCH_OMAP2PLUS), y)
+
+obj-y += clk.o omap4-cm.o
+obj-$(CONFIG_AM33XX) += am3-prcm.o
+
+endif # CONFIG_ARCH_OMAP2PLUS
+
 obj-$(CONFIG_CLK_TI_AM3_DPLL) += clk-am3-dpll.o clk-am3-dpll-x2.o
 obj-$(CONFIG_CLK_TI_CTRL) += clk-ctrl.o
 obj-$(CONFIG_CLK_TI_DIVIDER) += clk-divider.o
diff --git a/drivers/clk/ti/am3-prcm.c b/drivers/clk/ti/am3-prcm.c
new file mode 100644
index 0000000000..08e84093f5
--- /dev/null
+++ b/drivers/clk/ti/am3-prcm.c
@@ -0,0 +1,65 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * AM335x power reset and clock manager (prcm)
+ *
+ * Copyright (C) 2020 Dario Binacchi <dariobin@libero.it>
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <dm/lists.h>
+#include <linux/err.h>
+
+static int ti_am3_prcm_bind(struct udevice *dev)
+{
+	ofnode clocks_node, node;
+	int err;
+
+	if (!strcmp("clocks", ofnode_get_name(dev_ofnode(dev)))) {
+		ofnode_for_each_subnode(node, dev_ofnode(dev)) {
+			dev_dbg(dev, "%s: node=%s\n", __func__,
+				ofnode_get_name(node));
+			err = lists_bind_fdt(dev, node, NULL, false);
+			if (err) {
+				dev_err(dev, "%s: lists_bind_fdt, err=%d\n",
+					__func__, err);
+				return err;
+			}
+		}
+
+		return 0;
+	}
+
+	err = dm_scan_fdt_dev(dev);
+	if (err) {
+		dev_err(dev, "%s: dm_scan_fdt, err=%d\n", __func__, err);
+		return err;
+	}
+
+	clocks_node = ofnode_find_subnode(dev_ofnode(dev), "clocks");
+	if (!ofnode_valid(clocks_node)) {
+		dev_err(dev, "%s: failed to get clocks sub-node\n", __func__);
+		return -ENODEV;
+	}
+
+	err = device_bind_driver_to_node(dev, "ti_am3_prcm", "prcm_clocks",
+					 clocks_node, NULL);
+	if (err) {
+		dev_err(dev, "%s: failed to bind prcm_clocks\n", __func__);
+		return err;
+	}
+
+	return 0;
+}
+
+static const struct udevice_id ti_am3_prcm_ids[] = {
+	{.compatible = "ti,am3-prcm"},
+	{}
+};
+
+U_BOOT_DRIVER(ti_am3_prcm) = {
+	.name = "ti_am3_prcm",
+	.id = UCLASS_SIMPLE_BUS,
+	.of_match = ti_am3_prcm_ids,
+	.bind = ti_am3_prcm_bind,
+};
-- 
2.17.1