clk: tango4: clkgen driver for Tango4 platforms

Provide support for Sigma Designs Tango4 clock generator.
NOTE: This driver is incompatible with Tango3 clkgen.

Signed-off-by: Marc Gonzalez <[e-mail]>
[[e-mail]: Add kernel.h include for panic/sprintf]
Signed-off-by: Stephen Boyd <[e-mail]>

Documentation/devicetree/bindings/clock/tango4-clock.txt

···
+* Sigma Designs Tango4 Clock Generator
+
+The Tango4 clock generator outputs cpu_clk and sys_clk (the latter is used
+for RAM and various peripheral devices). The clock binding described here
+is applicable to all Tango4 SoCs.
+
+Required Properties:
+
+- compatible: should be "sigma,tango4-clkgen".
+- reg: physical base address of the device and length of memory mapped region.
+- clocks: phandle of the input clock (crystal oscillator).
+- clock-output-names: should be "cpuclk" and "sysclk".
+- #clock-cells: should be set to 1.
+
+Example:
+
+	clkgen: clkgen@10000 {
+		compatible = "sigma,tango4-clkgen";
+		reg = <0x10000 0x40>;
+		clocks = <&xtal>;
+		clock-output-names = "cpuclk", "sysclk";
+		#clock-cells = <1>;
+	};

drivers/clk/Makefile

···
 obj-$(CONFIG_COMMON_CLK_SI570)		+= clk-si570.o
 obj-$(CONFIG_COMMON_CLK_CDCE925)	+= clk-cdce925.o
 obj-$(CONFIG_ARCH_STM32)		+= clk-stm32f4.o
+obj-$(CONFIG_ARCH_TANGOX)		+= clk-tango4.o
 obj-$(CONFIG_CLK_TWL6040)		+= clk-twl6040.o
 obj-$(CONFIG_ARCH_U300)			+= clk-u300.o
 obj-$(CONFIG_ARCH_VT8500)		+= clk-vt8500.o

drivers/clk/clk-tango4.c

···
+#include <linux/kernel.h>
+#include <linux/clk-provider.h>
+#include <linux/of_address.h>
+#include <linux/init.h>
+#include <linux/io.h>
+
+static struct clk *out[2];
+static struct clk_onecell_data clk_data = { out, 2 };
+
+#define SYSCLK_CTRL	0x20
+#define CPUCLK_CTRL	0x24
+#define LEGACY_DIV	0x3c
+
+#define PLL_N(val)	(((val) >>  0) & 0x7f)
+#define PLL_K(val)	(((val) >> 13) & 0x7)
+#define PLL_M(val)	(((val) >> 16) & 0x7)
+#define DIV_INDEX(val)	(((val) >>  8) & 0xf)
+
+static void __init make_pll(int idx, const char *parent, void __iomem *base)
+{
+	char name[8];
+	u32 val, mul, div;
+
+	sprintf(name, "pll%d", idx);
+	val = readl_relaxed(base + idx*8);
+	mul =  PLL_N(val) + 1;
+	div = (PLL_M(val) + 1) << PLL_K(val);
+	clk_register_fixed_factor(NULL, name, parent, 0, mul, div);
+}
+
+static int __init get_div(void __iomem *base)
+{
+	u8 sysclk_tab[16] = { 2, 4, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4 };
+	int idx = DIV_INDEX(readl_relaxed(base + LEGACY_DIV));
+
+	return sysclk_tab[idx];
+}
+
+static void __init tango4_clkgen_setup(struct device_node *np)
+{
+	int div, ret;
+	void __iomem *base = of_iomap(np, 0);
+	const char *parent = of_clk_get_parent_name(np, 0);
+
+	if (!base)
+		panic("%s: invalid address\n", np->full_name);
+
+	make_pll(0, parent, base);
+	make_pll(1, parent, base);
+
+	out[0] = clk_register_divider(NULL, "cpuclk", "pll0", 0,
+			base + CPUCLK_CTRL, 8, 8, CLK_DIVIDER_ONE_BASED, NULL);
+
+	div = readl_relaxed(base + SYSCLK_CTRL) & BIT(23) ? get_div(base) : 4;
+	out[1] = clk_register_fixed_factor(NULL, "sysclk", "pll1", 0, 1, div);
+
+	ret = of_clk_add_provider(np, of_clk_src_onecell_get, &clk_data);
+	if (IS_ERR(out[0]) || IS_ERR(out[1]) || ret < 0)
+		panic("%s: clk registration failed\n", np->full_name);
+}
+CLK_OF_DECLARE(tango4_clkgen, "sigma,tango4-clkgen", tango4_clkgen_setup);