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-dt 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/pl320-ipc.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-dt", };
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 		(!of_machine_is_compatible("calxeda,ecx-2000")))
71 		return -ENODEV;
72 
73 	cpu_dev = get_cpu_device(0);
74 	if (!cpu_dev) {
75 		pr_err("failed to get highbank cpufreq device\n");
76 		return -ENODEV;
77 	}
78 
79 	np = of_node_get(cpu_dev->of_node);
80 	if (!np) {
81 		pr_err("failed to find highbank cpufreq node\n");
82 		return -ENOENT;
83 	}
84 
85 	cpu_clk = clk_get(cpu_dev, NULL);
86 	if (IS_ERR(cpu_clk)) {
87 		ret = PTR_ERR(cpu_clk);
88 		pr_err("failed to get cpu0 clock: %d\n", ret);
89 		goto out_put_node;
90 	}
91 
92 	ret = clk_notifier_register(cpu_clk, &hb_cpufreq_clk_nb);
93 	if (ret) {
94 		pr_err("failed to register clk notifier: %d\n", ret);
95 		goto out_put_node;
96 	}
97 
98 	/* Instantiate cpufreq-dt */
99 	platform_device_register_full(&devinfo);
100 
101 out_put_node:
102 	of_node_put(np);
103 	return ret;
104 }
105 module_init(hb_cpufreq_driver_init);
106 
107 MODULE_AUTHOR("Mark Langsdorf <mark.langsdorf@calxeda.com>");
108 MODULE_DESCRIPTION("Calxeda Highbank cpufreq driver");
109 MODULE_LICENSE("GPL");
110