1 /*
2  *	kirkwood_freq.c: cpufreq driver for the Marvell kirkwood
3  *
4  *	Copyright (C) 2013 Andrew Lunn <andrew@lunn.ch>
5  *
6  *	This program is free software; you can redistribute it and/or
7  *	modify it under the terms of the GNU General Public License
8  *	as published by the Free Software Foundation; either version
9  *	2 of the License, or (at your option) any later version.
10  */
11 
12 #include <linux/kernel.h>
13 #include <linux/module.h>
14 #include <linux/clk.h>
15 #include <linux/cpufreq.h>
16 #include <linux/of_device.h>
17 #include <linux/platform_device.h>
18 #include <linux/io.h>
19 #include <asm/proc-fns.h>
20 
21 #define CPU_SW_INT_BLK BIT(28)
22 
23 static struct priv
24 {
25 	struct clk *cpu_clk;
26 	struct clk *ddr_clk;
27 	struct clk *powersave_clk;
28 	struct device *dev;
29 	void __iomem *base;
30 } priv;
31 
32 #define STATE_CPU_FREQ 0x01
33 #define STATE_DDR_FREQ 0x02
34 
35 /*
36  * Kirkwood can swap the clock to the CPU between two clocks:
37  *
38  * - cpu clk
39  * - ddr clk
40  *
41  * The frequencies are set at runtime before registering this table.
42  */
43 static struct cpufreq_frequency_table kirkwood_freq_table[] = {
44 	{0, STATE_CPU_FREQ,	0}, /* CPU uses cpuclk */
45 	{0, STATE_DDR_FREQ,	0}, /* CPU uses ddrclk */
46 	{0, 0,			CPUFREQ_TABLE_END},
47 };
48 
49 static unsigned int kirkwood_cpufreq_get_cpu_frequency(unsigned int cpu)
50 {
51 	return clk_get_rate(priv.powersave_clk) / 1000;
52 }
53 
54 static int kirkwood_cpufreq_target(struct cpufreq_policy *policy,
55 			    unsigned int index)
56 {
57 	unsigned int state = kirkwood_freq_table[index].driver_data;
58 	unsigned long reg;
59 
60 	local_irq_disable();
61 
62 	/* Disable interrupts to the CPU */
63 	reg = readl_relaxed(priv.base);
64 	reg |= CPU_SW_INT_BLK;
65 	writel_relaxed(reg, priv.base);
66 
67 	switch (state) {
68 	case STATE_CPU_FREQ:
69 		clk_set_parent(priv.powersave_clk, priv.cpu_clk);
70 		break;
71 	case STATE_DDR_FREQ:
72 		clk_set_parent(priv.powersave_clk, priv.ddr_clk);
73 		break;
74 	}
75 
76 	/* Wait-for-Interrupt, while the hardware changes frequency */
77 	cpu_do_idle();
78 
79 	/* Enable interrupts to the CPU */
80 	reg = readl_relaxed(priv.base);
81 	reg &= ~CPU_SW_INT_BLK;
82 	writel_relaxed(reg, priv.base);
83 
84 	local_irq_enable();
85 
86 	return 0;
87 }
88 
89 /* Module init and exit code */
90 static int kirkwood_cpufreq_cpu_init(struct cpufreq_policy *policy)
91 {
92 	return cpufreq_generic_init(policy, kirkwood_freq_table, 5000);
93 }
94 
95 static struct cpufreq_driver kirkwood_cpufreq_driver = {
96 	.flags	= CPUFREQ_NEED_INITIAL_FREQ_CHECK,
97 	.get	= kirkwood_cpufreq_get_cpu_frequency,
98 	.verify	= cpufreq_generic_frequency_table_verify,
99 	.target_index = kirkwood_cpufreq_target,
100 	.init	= kirkwood_cpufreq_cpu_init,
101 	.name	= "kirkwood-cpufreq",
102 	.attr	= cpufreq_generic_attr,
103 };
104 
105 static int kirkwood_cpufreq_probe(struct platform_device *pdev)
106 {
107 	struct device_node *np;
108 	struct resource *res;
109 	int err;
110 
111 	priv.dev = &pdev->dev;
112 
113 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
114 	priv.base = devm_ioremap_resource(&pdev->dev, res);
115 	if (IS_ERR(priv.base))
116 		return PTR_ERR(priv.base);
117 
118 	np = of_cpu_device_node_get(0);
119 	if (!np) {
120 		dev_err(&pdev->dev, "failed to get cpu device node\n");
121 		return -ENODEV;
122 	}
123 
124 	priv.cpu_clk = of_clk_get_by_name(np, "cpu_clk");
125 	if (IS_ERR(priv.cpu_clk)) {
126 		dev_err(priv.dev, "Unable to get cpuclk");
127 		return PTR_ERR(priv.cpu_clk);
128 	}
129 
130 	clk_prepare_enable(priv.cpu_clk);
131 	kirkwood_freq_table[0].frequency = clk_get_rate(priv.cpu_clk) / 1000;
132 
133 	priv.ddr_clk = of_clk_get_by_name(np, "ddrclk");
134 	if (IS_ERR(priv.ddr_clk)) {
135 		dev_err(priv.dev, "Unable to get ddrclk");
136 		err = PTR_ERR(priv.ddr_clk);
137 		goto out_cpu;
138 	}
139 
140 	clk_prepare_enable(priv.ddr_clk);
141 	kirkwood_freq_table[1].frequency = clk_get_rate(priv.ddr_clk) / 1000;
142 
143 	priv.powersave_clk = of_clk_get_by_name(np, "powersave");
144 	if (IS_ERR(priv.powersave_clk)) {
145 		dev_err(priv.dev, "Unable to get powersave");
146 		err = PTR_ERR(priv.powersave_clk);
147 		goto out_ddr;
148 	}
149 	clk_prepare_enable(priv.powersave_clk);
150 
151 	of_node_put(np);
152 	np = NULL;
153 
154 	err = cpufreq_register_driver(&kirkwood_cpufreq_driver);
155 	if (!err)
156 		return 0;
157 
158 	dev_err(priv.dev, "Failed to register cpufreq driver");
159 
160 	clk_disable_unprepare(priv.powersave_clk);
161 out_ddr:
162 	clk_disable_unprepare(priv.ddr_clk);
163 out_cpu:
164 	clk_disable_unprepare(priv.cpu_clk);
165 	of_node_put(np);
166 
167 	return err;
168 }
169 
170 static int kirkwood_cpufreq_remove(struct platform_device *pdev)
171 {
172 	cpufreq_unregister_driver(&kirkwood_cpufreq_driver);
173 
174 	clk_disable_unprepare(priv.powersave_clk);
175 	clk_disable_unprepare(priv.ddr_clk);
176 	clk_disable_unprepare(priv.cpu_clk);
177 
178 	return 0;
179 }
180 
181 static struct platform_driver kirkwood_cpufreq_platform_driver = {
182 	.probe = kirkwood_cpufreq_probe,
183 	.remove = kirkwood_cpufreq_remove,
184 	.driver = {
185 		.name = "kirkwood-cpufreq",
186 	},
187 };
188 
189 module_platform_driver(kirkwood_cpufreq_platform_driver);
190 
191 MODULE_LICENSE("GPL v2");
192 MODULE_AUTHOR("Andrew Lunn <andrew@lunn.ch");
193 MODULE_DESCRIPTION("cpufreq driver for Marvell's kirkwood CPU");
194 MODULE_ALIAS("platform:kirkwood-cpufreq");
195