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 	int i;
32 	u32 msg[HB_CPUFREQ_IPC_LEN];
33 
34 	msg[0] = HB_CPUFREQ_CHANGE_NOTE;
35 	msg[1] = freq / 1000000;
36 	for (i = 2; i < HB_CPUFREQ_IPC_LEN; i++)
37 		msg[i] = 0;
38 
39 	return pl320_ipc_transmit(msg);
40 }
41 
42 static int hb_cpufreq_clk_notify(struct notifier_block *nb,
43 				unsigned long action, void *hclk)
44 {
45 	struct clk_notifier_data *clk_data = hclk;
46 	int i = 0;
47 
48 	if (action == PRE_RATE_CHANGE) {
49 		if (clk_data->new_rate > clk_data->old_rate)
50 			while (hb_voltage_change(clk_data->new_rate))
51 				if (i++ > HB_CPUFREQ_VOLT_RETRIES)
52 					return NOTIFY_BAD;
53 	} else if (action == POST_RATE_CHANGE) {
54 		if (clk_data->new_rate < clk_data->old_rate)
55 			while (hb_voltage_change(clk_data->new_rate))
56 				if (i++ > HB_CPUFREQ_VOLT_RETRIES)
57 					return NOTIFY_BAD;
58 	}
59 
60 	return NOTIFY_DONE;
61 }
62 
63 static struct notifier_block hb_cpufreq_clk_nb = {
64 	.notifier_call = hb_cpufreq_clk_notify,
65 };
66 
67 static int hb_cpufreq_driver_init(void)
68 {
69 	struct platform_device_info devinfo = { .name = "cpufreq-cpu0", };
70 	struct device *cpu_dev;
71 	struct clk *cpu_clk;
72 	struct device_node *np;
73 	int ret;
74 
75 	if (!of_machine_is_compatible("calxeda,highbank"))
76 		return -ENODEV;
77 
78 	for_each_child_of_node(of_find_node_by_path("/cpus"), np)
79 		if (of_get_property(np, "operating-points", NULL))
80 			break;
81 
82 	if (!np) {
83 		pr_err("failed to find highbank cpufreq node\n");
84 		return -ENOENT;
85 	}
86 
87 	cpu_dev = get_cpu_device(0);
88 	if (!cpu_dev) {
89 		pr_err("failed to get highbank cpufreq device\n");
90 		ret = -ENODEV;
91 		goto out_put_node;
92 	}
93 
94 	cpu_dev->of_node = np;
95 
96 	cpu_clk = clk_get(cpu_dev, NULL);
97 	if (IS_ERR(cpu_clk)) {
98 		ret = PTR_ERR(cpu_clk);
99 		pr_err("failed to get cpu0 clock: %d\n", ret);
100 		goto out_put_node;
101 	}
102 
103 	ret = clk_notifier_register(cpu_clk, &hb_cpufreq_clk_nb);
104 	if (ret) {
105 		pr_err("failed to register clk notifier: %d\n", ret);
106 		goto out_put_node;
107 	}
108 
109 	/* Instantiate cpufreq-cpu0 */
110 	platform_device_register_full(&devinfo);
111 
112 out_put_node:
113 	of_node_put(np);
114 	return ret;
115 }
116 module_init(hb_cpufreq_driver_init);
117 
118 MODULE_AUTHOR("Mark Langsdorf <mark.langsdorf@calxeda.com>");
119 MODULE_DESCRIPTION("Calxeda Highbank cpufreq driver");
120 MODULE_LICENSE("GPL");
121