clk: Add axi-clkgen driver

This driver adds support for the AXI clkgen pcore to the common clock framework.
The AXI clkgen pcore is a AXI front-end to the MMCM_ADV frequency synthesizer
commonly found in Xilinx FPGAs.

The AXI clkgen pcore is used in Analog Devices' reference designs targeting
Xilinx FPGAs.

Signed-off-by: Lars-Peter Clausen <[e-mail]>
Signed-off-by: Mike Turquette <[e-mail]>

Documentation/devicetree/bindings/clock/axi-clkgen.txt

···
+Binding for the axi-clkgen clock generator
+
+This binding uses the common clock binding[1].
+
+[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
+
+Required properties:
+- compatible : shall be "adi,axi-clkgen".
+- #clock-cells : from common clock binding; Should always be set to 0.
+- reg : Address and length of the axi-clkgen register set.
+- clocks : Phandle and clock specifier for the parent clock.
+
+Optional properties:
+- clock-output-names : From common clock binding.
+
+Example:
+	clock@0xff000000 {
+		compatible = "adi,axi-clkgen";
+		#clock-cells = <0>;
+		reg = <0xff000000 0x1000>;
+		clocks = <&osc 1>;
+	};

drivers/clk/Kconfig

···
 	  McPDM. McPDM module is using the external bit clock on the McPDM bus
 	  as functional clock.
 
+config COMMON_CLK_AXI_CLKGEN
+	tristate "AXI clkgen driver"
+	depends on ARCH_ZYNQ || MICROBLAZE
+	help
+	---help---
+	  Support for the Analog Devices axi-clkgen pcore clock generator for Xilinx
+	  FPGAs. It is commonly used in Analog Devices' reference designs.
+
 endmenu
 
 source "drivers/clk/mvebu/Kconfig"

drivers/clk/Makefile

···
 obj-$(CONFIG_X86)		+= x86/
 
 # Chip specific
+obj-$(CONFIG_COMMON_CLK_AXI_CLKGEN) += clk-axi-clkgen.o
 obj-$(CONFIG_COMMON_CLK_WM831X) += clk-wm831x.o
 obj-$(CONFIG_COMMON_CLK_MAX77686) += clk-max77686.o
 obj-$(CONFIG_CLK_TWL6040)	+= clk-twl6040.o

drivers/clk/clk-axi-clkgen.c

···
+/*
+ * AXI clkgen driver
+ *
+ * Copyright 2012-2013 Analog Devices Inc.
+ *  Author: Lars-Peter Clausen <[e-mail]>
+ *
+ * Licensed under the GPL-2.
+ *
+ */
+
+#include <linux/platform_device.h>
+#include <linux/clk-provider.h>
+#include <linux/clk.h>
+#include <linux/slab.h>
+#include <linux/io.h>
+#include <linux/of.h>
+#include <linux/module.h>
+#include <linux/err.h>
+
+#define AXI_CLKGEN_REG_UPDATE_ENABLE	0x04
+#define AXI_CLKGEN_REG_CLK_OUT1		0x08
+#define AXI_CLKGEN_REG_CLK_OUT2		0x0c
+#define AXI_CLKGEN_REG_CLK_DIV		0x10
+#define AXI_CLKGEN_REG_CLK_FB1		0x14
+#define AXI_CLKGEN_REG_CLK_FB2		0x18
+#define AXI_CLKGEN_REG_LOCK1		0x1c
+#define AXI_CLKGEN_REG_LOCK2		0x20
+#define AXI_CLKGEN_REG_LOCK3		0x24
+#define AXI_CLKGEN_REG_FILTER1		0x28
+#define AXI_CLKGEN_REG_FILTER2		0x2c
+
+struct axi_clkgen {
+	void __iomem *base;
+	struct clk_hw clk_hw;
+};
+
+static uint32_t axi_clkgen_lookup_filter(unsigned int m)
+{
+	switch (m) {
+	case 0:
+		return 0x01001990;
+	case 1:
+		return 0x01001190;
+	case 2:
+		return 0x01009890;
+	case 3:
+		return 0x01001890;
+	case 4:
+		return 0x01008890;
+	case 5 ... 8:
+		return 0x01009090;
+	case 9 ... 11:
+		return 0x01000890;
+	case 12:
+		return 0x08009090;
+	case 13 ... 22:
+		return 0x01001090;
+	case 23 ... 36:
+		return 0x01008090;
+	case 37 ... 46:
+		return 0x08001090;
+	default:
+		return 0x08008090;
+	}
+}
+
+static const uint32_t axi_clkgen_lock_table[] = {
+	0x060603e8, 0x060603e8, 0x080803e8, 0x0b0b03e8,
+	0x0e0e03e8, 0x111103e8, 0x131303e8, 0x161603e8,
+	0x191903e8, 0x1c1c03e8, 0x1f1f0384, 0x1f1f0339,
+	0x1f1f02ee, 0x1f1f02bc, 0x1f1f028a, 0x1f1f0271,
+	0x1f1f023f, 0x1f1f0226, 0x1f1f020d, 0x1f1f01f4,
+	0x1f1f01db, 0x1f1f01c2, 0x1f1f01a9, 0x1f1f0190,
+	0x1f1f0190, 0x1f1f0177, 0x1f1f015e, 0x1f1f015e,
+	0x1f1f0145, 0x1f1f0145, 0x1f1f012c, 0x1f1f012c,
+	0x1f1f012c, 0x1f1f0113, 0x1f1f0113, 0x1f1f0113,
+};
+
+static uint32_t axi_clkgen_lookup_lock(unsigned int m)
+{
+	if (m < ARRAY_SIZE(axi_clkgen_lock_table))
+		return axi_clkgen_lock_table[m];
+	return 0x1f1f00fa;
+}
+
+static const unsigned int fpfd_min = 10000;
+static const unsigned int fpfd_max = 300000;
+static const unsigned int fvco_min = 600000;
+static const unsigned int fvco_max = 1200000;
+
+static void axi_clkgen_calc_params(unsigned long fin, unsigned long fout,
+	unsigned int *best_d, unsigned int *best_m, unsigned int *best_dout)
+{
+	unsigned long d, d_min, d_max, _d_min, _d_max;
+	unsigned long m, m_min, m_max;
+	unsigned long f, dout, best_f, fvco;
+
+	fin /= 1000;
+	fout /= 1000;
+
+	best_f = ULONG_MAX;
+	*best_d = 0;
+	*best_m = 0;
+	*best_dout = 0;
+
+	d_min = max_t(unsigned long, DIV_ROUND_UP(fin, fpfd_max), 1);
+	d_max = min_t(unsigned long, fin / fpfd_min, 80);
+
+	m_min = max_t(unsigned long, DIV_ROUND_UP(fvco_min, fin) * d_min, 1);
+	m_max = min_t(unsigned long, fvco_max * d_max / fin, 64);
+
+	for (m = m_min; m <= m_max; m++) {
+		_d_min = max(d_min, DIV_ROUND_UP(fin * m, fvco_max));
+		_d_max = min(d_max, fin * m / fvco_min);
+
+		for (d = _d_min; d <= _d_max; d++) {
+			fvco = fin * m / d;
+
+			dout = DIV_ROUND_CLOSEST(fvco, fout);
+			dout = clamp_t(unsigned long, dout, 1, 128);
+			f = fvco / dout;
+			if (abs(f - fout) < abs(best_f - fout)) {
+				best_f = f;
+				*best_d = d;
+				*best_m = m;
+				*best_dout = dout;
+				if (best_f == fout)
+					return;
+			}
+		}
+	}
+}
+
+static void axi_clkgen_calc_clk_params(unsigned int divider, unsigned int *low,
+	unsigned int *high, unsigned int *edge, unsigned int *nocount)
+{
+	if (divider == 1)
+		*nocount = 1;
+	else
+		*nocount = 0;
+
+	*high = divider / 2;
+	*edge = divider % 2;
+	*low = divider - *high;
+}
+
+static void axi_clkgen_write(struct axi_clkgen *axi_clkgen,
+	unsigned int reg, unsigned int val)
+{
+	writel(val, axi_clkgen->base + reg);
+}
+
+static void axi_clkgen_read(struct axi_clkgen *axi_clkgen,
+	unsigned int reg, unsigned int *val)
+{
+	*val = readl(axi_clkgen->base + reg);
+}
+
+static struct axi_clkgen *clk_hw_to_axi_clkgen(struct clk_hw *clk_hw)
+{
+	return container_of(clk_hw, struct axi_clkgen, clk_hw);
+}
+
+static int axi_clkgen_set_rate(struct clk_hw *clk_hw,
+	unsigned long rate, unsigned long parent_rate)
+{
+	struct axi_clkgen *axi_clkgen = clk_hw_to_axi_clkgen(clk_hw);
+	unsigned int d, m, dout;
+	unsigned int nocount;
+	unsigned int high;
+	unsigned int edge;
+	unsigned int low;
+	uint32_t filter;
+	uint32_t lock;
+
+	if (parent_rate == 0 || rate == 0)
+		return -EINVAL;
+
+	axi_clkgen_calc_params(parent_rate, rate, &d, &m, &dout);
+
+	if (d == 0 || dout == 0 || m == 0)
+		return -EINVAL;
+
+	filter = axi_clkgen_lookup_filter(m - 1);
+	lock = axi_clkgen_lookup_lock(m - 1);
+
+	axi_clkgen_write(axi_clkgen, AXI_CLKGEN_REG_UPDATE_ENABLE, 0);
+
+	axi_clkgen_calc_clk_params(dout, &low, &high, &edge, &nocount);
+	axi_clkgen_write(axi_clkgen, AXI_CLKGEN_REG_CLK_OUT1,
+		(high << 6) | low);
+	axi_clkgen_write(axi_clkgen, AXI_CLKGEN_REG_CLK_OUT2,
+		(edge << 7) | (nocount << 6));
+
+	axi_clkgen_calc_clk_params(d, &low, &high, &edge, &nocount);
+	axi_clkgen_write(axi_clkgen, AXI_CLKGEN_REG_CLK_DIV,
+		(edge << 13) | (nocount << 12) | (high << 6) | low);
+
+	axi_clkgen_calc_clk_params(m, &low, &high, &edge, &nocount);
+	axi_clkgen_write(axi_clkgen, AXI_CLKGEN_REG_CLK_FB1,
+		(high << 6) | low);
+	axi_clkgen_write(axi_clkgen, AXI_CLKGEN_REG_CLK_FB2,
+		(edge << 7) | (nocount << 6));
+
+	axi_clkgen_write(axi_clkgen, AXI_CLKGEN_REG_LOCK1, lock & 0x3ff);
+	axi_clkgen_write(axi_clkgen, AXI_CLKGEN_REG_LOCK2,
+		(((lock >> 16) & 0x1f) << 10) | 0x1);
+	axi_clkgen_write(axi_clkgen, AXI_CLKGEN_REG_LOCK3,
+		(((lock >> 24) & 0x1f) << 10) | 0x3e9);
+	axi_clkgen_write(axi_clkgen, AXI_CLKGEN_REG_FILTER1, filter >> 16);
+	axi_clkgen_write(axi_clkgen, AXI_CLKGEN_REG_FILTER2, filter);
+
+	axi_clkgen_write(axi_clkgen, AXI_CLKGEN_REG_UPDATE_ENABLE, 1);
+
+	return 0;
+}
+
+static long axi_clkgen_round_rate(struct clk_hw *hw, unsigned long rate,
+	unsigned long *parent_rate)
+{
+	unsigned int d, m, dout;
+
+	axi_clkgen_calc_params(*parent_rate, rate, &d, &m, &dout);
+
+	if (d == 0 || dout == 0 || m == 0)
+		return -EINVAL;
+
+	return *parent_rate / d * m / dout;
+}
+
+static unsigned long axi_clkgen_recalc_rate(struct clk_hw *clk_hw,
+	unsigned long parent_rate)
+{
+	struct axi_clkgen *axi_clkgen = clk_hw_to_axi_clkgen(clk_hw);
+	unsigned int d, m, dout;
+	unsigned int reg;
+	unsigned long long tmp;
+
+	axi_clkgen_read(axi_clkgen, AXI_CLKGEN_REG_CLK_OUT1, &reg);
+	dout = (reg & 0x3f) + ((reg >> 6) & 0x3f);
+	axi_clkgen_read(axi_clkgen, AXI_CLKGEN_REG_CLK_DIV, &reg);
+	d = (reg & 0x3f) + ((reg >> 6) & 0x3f);
+	axi_clkgen_read(axi_clkgen, AXI_CLKGEN_REG_CLK_FB1, &reg);
+	m = (reg & 0x3f) + ((reg >> 6) & 0x3f);
+
+	if (d == 0 || dout == 0)
+		return 0;
+
+	tmp = (unsigned long long)(parent_rate / d) * m;
+	do_div(tmp, dout);
+
+	if (tmp > ULONG_MAX)
+		return ULONG_MAX;
+
+	return tmp;
+}
+
+static const struct clk_ops axi_clkgen_ops = {
+	.recalc_rate = axi_clkgen_recalc_rate,
+	.round_rate = axi_clkgen_round_rate,
+	.set_rate = axi_clkgen_set_rate,
+};
+
+static int axi_clkgen_probe(struct platform_device *pdev)
+{
+	struct axi_clkgen *axi_clkgen;
+	struct clk_init_data init;
+	const char *parent_name;
+	const char *clk_name;
+	struct resource *mem;
+	struct clk *clk;
+
+	axi_clkgen = devm_kzalloc(&pdev->dev, sizeof(*axi_clkgen), GFP_KERNEL);
+	if (!axi_clkgen)
+		return -ENOMEM;
+
+	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	axi_clkgen->base = devm_ioremap_resource(&pdev->dev, mem);
+	if (IS_ERR(axi_clkgen->base))
+		return PTR_ERR(axi_clkgen->base);
+
+	parent_name = of_clk_get_parent_name(pdev->dev.of_node, 0);
+	if (!parent_name)
+		return -EINVAL;
+
+	clk_name = pdev->dev.of_node->name;
+	of_property_read_string(pdev->dev.of_node, "clock-output-names",
+		&clk_name);
+
+	init.name = clk_name;
+	init.ops = &axi_clkgen_ops;
+	init.flags = 0;
+	init.parent_names = &parent_name;
+	init.num_parents = 1;
+
+	axi_clkgen->clk_hw.init = &init;
+	clk = devm_clk_register(&pdev->dev, &axi_clkgen->clk_hw);
+	if (IS_ERR(clk))
+		return PTR_ERR(clk);
+
+	return of_clk_add_provider(pdev->dev.of_node, of_clk_src_simple_get,
+				    clk);
+}
+
+static int axi_clkgen_remove(struct platform_device *pdev)
+{
+	of_clk_del_provider(pdev->dev.of_node);
+
+	return 0;
+}
+
+static const struct of_device_id axi_clkgen_ids[] = {
+	{ .compatible = "adi,axi-clkgen-1.00.a" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, axi_clkgen_ids);
+
+static struct platform_driver axi_clkgen_driver = {
+	.driver = {
+		.name = "adi-axi-clkgen",
+		.owner = THIS_MODULE,
+		.of_match_table = axi_clkgen_ids,
+	},
+	.probe = axi_clkgen_probe,
+	.remove = axi_clkgen_remove,
+};
+module_platform_driver(axi_clkgen_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Lars-Peter Clausen <[e-mail]>");
+MODULE_DESCRIPTION("Driver for the Analog Devices' AXI clkgen pcore clock generator");