1 /*
2  * Copyright (C) 2012 Calxeda, Inc.
3  *
4  * This program is free software; you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License version 2 as
6  * published by the Free Software Foundation.
7  *
8  * This driver provides the clk notifier callbacks that are used when
9  * the cpufreq-cpu0 driver changes to frequency to alert the highbank
10  * EnergyCore Management Engine (ECME) about the need to change
11  * voltage. The ECME interfaces with the actual voltage regulators.
12  */
13 
14 #define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
15 
16 #include <linux/kernel.h>
17 #include <linux/module.h>
18 #include <linux/clk.h>
19 #include <linux/cpu.h>
20 #include <linux/err.h>
21 #include <linux/of.h>
22 #include <linux/mailbox.h>
23 #include <linux/platform_device.h>
24 
25 #define HB_CPUFREQ_CHANGE_NOTE	0x80000001
26 #define HB_CPUFREQ_IPC_LEN	7
27 #define HB_CPUFREQ_VOLT_RETRIES	15
28 
29 static int hb_voltage_change(unsigned int freq)
30 {
31 	u32 msg[HB_CPUFREQ_IPC_LEN] = {HB_CPUFREQ_CHANGE_NOTE, freq / 1000000};
32 
33 	return pl320_ipc_transmit(msg);
34 }
35 
36 static int hb_cpufreq_clk_notify(struct notifier_block *nb,
37 				unsigned long action, void *hclk)
38 {
39 	struct clk_notifier_data *clk_data = hclk;
40 	int i = 0;
41 
42 	if (action == PRE_RATE_CHANGE) {
43 		if (clk_data->new_rate > clk_data->old_rate)
44 			while (hb_voltage_change(clk_data->new_rate))
45 				if (i++ > HB_CPUFREQ_VOLT_RETRIES)
46 					return NOTIFY_BAD;
47 	} else if (action == POST_RATE_CHANGE) {
48 		if (clk_data->new_rate < clk_data->old_rate)
49 			while (hb_voltage_change(clk_data->new_rate))
50 				if (i++ > HB_CPUFREQ_VOLT_RETRIES)
51 					return NOTIFY_BAD;
52 	}
53 
54 	return NOTIFY_DONE;
55 }
56 
57 static struct notifier_block hb_cpufreq_clk_nb = {
58 	.notifier_call = hb_cpufreq_clk_notify,
59 };
60 
61 static int hb_cpufreq_driver_init(void)
62 {
63 	struct platform_device_info devinfo = { .name = "cpufreq-cpu0", };
64 	struct device *cpu_dev;
65 	struct clk *cpu_clk;
66 	struct device_node *np;
67 	int ret;
68 
69 	if (!of_machine_is_compatible("calxeda,highbank"))
70 		return -ENODEV;
71 
72 	for_each_child_of_node(of_find_node_by_path("/cpus"), np)
73 		if (of_get_property(np, "operating-points", NULL))
74 			break;
75 
76 	if (!np) {
77 		pr_err("failed to find highbank cpufreq node\n");
78 		return -ENOENT;
79 	}
80 
81 	cpu_dev = get_cpu_device(0);
82 	if (!cpu_dev) {
83 		pr_err("failed to get highbank cpufreq device\n");
84 		ret = -ENODEV;
85 		goto out_put_node;
86 	}
87 
88 	cpu_dev->of_node = np;
89 
90 	cpu_clk = clk_get(cpu_dev, NULL);
91 	if (IS_ERR(cpu_clk)) {
92 		ret = PTR_ERR(cpu_clk);
93 		pr_err("failed to get cpu0 clock: %d\n", ret);
94 		goto out_put_node;
95 	}
96 
97 	ret = clk_notifier_register(cpu_clk, &hb_cpufreq_clk_nb);
98 	if (ret) {
99 		pr_err("failed to register clk notifier: %d\n", ret);
100 		goto out_put_node;
101 	}
102 
103 	/* Instantiate cpufreq-cpu0 */
104 	platform_device_register_full(&devinfo);
105 
106 out_put_node:
107 	of_node_put(np);
108 	return ret;
109 }
110 module_init(hb_cpufreq_driver_init);
111 
112 MODULE_AUTHOR("Mark Langsdorf <mark.langsdorf@calxeda.com>");
113 MODULE_DESCRIPTION("Calxeda Highbank cpufreq driver");
114 MODULE_LICENSE("GPL");
115