1 /*
2  * Clocksource using the Low Power Timer found in the Low Power Controller (LPC)
3  *
4  * Copyright (C) 2015 STMicroelectronics – All Rights Reserved
5  *
6  * Author(s): Francesco Virlinzi <francesco.virlinzi@st.com>
7  *	      Ajit Pal Singh <ajitpal.singh@st.com>
8  *
9  * This program is free software; you can redistribute it and/or modify
10  * it under the terms of the GNU General Public License as published by
11  * the Free Software Foundation; either version 2 of the License, or
12  * (at your option) any later version.
13  */
14 
15 #include <linux/clk.h>
16 #include <linux/clocksource.h>
17 #include <linux/init.h>
18 #include <linux/of_address.h>
19 #include <linux/sched_clock.h>
20 #include <linux/slab.h>
21 
22 #include <dt-bindings/mfd/st-lpc.h>
23 
24 /* Low Power Timer */
25 #define LPC_LPT_LSB_OFF		0x400
26 #define LPC_LPT_MSB_OFF		0x404
27 #define LPC_LPT_START_OFF	0x408
28 
29 static struct st_clksrc_ddata {
30 	struct clk		*clk;
31 	void __iomem		*base;
32 } ddata;
33 
34 static void __init st_clksrc_reset(void)
35 {
36 	writel_relaxed(0, ddata.base + LPC_LPT_START_OFF);
37 	writel_relaxed(0, ddata.base + LPC_LPT_MSB_OFF);
38 	writel_relaxed(0, ddata.base + LPC_LPT_LSB_OFF);
39 	writel_relaxed(1, ddata.base + LPC_LPT_START_OFF);
40 }
41 
42 static u64 notrace st_clksrc_sched_clock_read(void)
43 {
44 	return (u64)readl_relaxed(ddata.base + LPC_LPT_LSB_OFF);
45 }
46 
47 static int __init st_clksrc_init(void)
48 {
49 	unsigned long rate;
50 	int ret;
51 
52 	st_clksrc_reset();
53 
54 	rate = clk_get_rate(ddata.clk);
55 
56 	sched_clock_register(st_clksrc_sched_clock_read, 32, rate);
57 
58 	ret = clocksource_mmio_init(ddata.base + LPC_LPT_LSB_OFF,
59 				    "clksrc-st-lpc", rate, 300, 32,
60 				    clocksource_mmio_readl_up);
61 	if (ret) {
62 		pr_err("clksrc-st-lpc: Failed to register clocksource\n");
63 		return ret;
64 	}
65 
66 	return 0;
67 }
68 
69 static int __init st_clksrc_setup_clk(struct device_node *np)
70 {
71 	struct clk *clk;
72 
73 	clk = of_clk_get(np, 0);
74 	if (IS_ERR(clk)) {
75 		pr_err("clksrc-st-lpc: Failed to get LPC clock\n");
76 		return PTR_ERR(clk);
77 	}
78 
79 	if (clk_prepare_enable(clk)) {
80 		pr_err("clksrc-st-lpc: Failed to enable LPC clock\n");
81 		return -EINVAL;
82 	}
83 
84 	if (!clk_get_rate(clk)) {
85 		pr_err("clksrc-st-lpc: Failed to get LPC clock rate\n");
86 		clk_disable_unprepare(clk);
87 		return -EINVAL;
88 	}
89 
90 	ddata.clk = clk;
91 
92 	return 0;
93 }
94 
95 static int __init st_clksrc_of_register(struct device_node *np)
96 {
97 	int ret;
98 	uint32_t mode;
99 
100 	ret = of_property_read_u32(np, "st,lpc-mode", &mode);
101 	if (ret) {
102 		pr_err("clksrc-st-lpc: An LPC mode must be provided\n");
103 		return ret;
104 	}
105 
106 	/* LPC can either run as a Clocksource or in RTC or WDT mode */
107 	if (mode != ST_LPC_MODE_CLKSRC)
108 		return 0;
109 
110 	ddata.base = of_iomap(np, 0);
111 	if (!ddata.base) {
112 		pr_err("clksrc-st-lpc: Unable to map iomem\n");
113 		return -ENXIO;
114 	}
115 
116 	ret = st_clksrc_setup_clk(np);
117 	if (ret) {
118 		iounmap(ddata.base);
119 		return ret;
120 	}
121 
122 	ret = st_clksrc_init();
123 	if (ret) {
124 		clk_disable_unprepare(ddata.clk);
125 		clk_put(ddata.clk);
126 		iounmap(ddata.base);
127 		return ret;
128 	}
129 
130 	pr_info("clksrc-st-lpc: clocksource initialised - running @ %luHz\n",
131 		clk_get_rate(ddata.clk));
132 
133 	return ret;
134 }
135 TIMER_OF_DECLARE(ddata, "st,stih407-lpc", st_clksrc_of_register);
136