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Linux/drivers/cpufreq/kirkwood-cpufreq.c

  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                 .owner = THIS_MODULE,
187         },
188 };
189 
190 module_platform_driver(kirkwood_cpufreq_platform_driver);
191 
192 MODULE_LICENSE("GPL v2");
193 MODULE_AUTHOR("Andrew Lunn <andrew@lunn.ch");
194 MODULE_DESCRIPTION("cpufreq driver for Marvell's kirkwood CPU");
195 MODULE_ALIAS("platform:kirkwood-cpufreq");
196 

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