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
st_clksrc_reset(void)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
st_clksrc_sched_clock_read(void)42 static u64 notrace st_clksrc_sched_clock_read(void)
43 {
44 return (u64)readl_relaxed(ddata.base + LPC_LPT_LSB_OFF);
45 }
46
st_clksrc_init(void)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
st_clksrc_setup_clk(struct device_node * np)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
st_clksrc_of_register(struct device_node * np)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
