1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Clocksource using the Low Power Timer found in the Low Power Controller (LPC)
4  *
5  * Copyright (C) 2015 STMicroelectronics – All Rights Reserved
6  *
7  * Author(s): Francesco Virlinzi <francesco.virlinzi@st.com>
8  *	      Ajit Pal Singh <ajitpal.singh@st.com>
9  */
10 
11 #include <linux/clk.h>
12 #include <linux/clocksource.h>
13 #include <linux/init.h>
14 #include <linux/of_address.h>
15 #include <linux/sched_clock.h>
16 #include <linux/slab.h>
17 
18 #include <dt-bindings/mfd/st-lpc.h>
19 
20 /* Low Power Timer */
21 #define LPC_LPT_LSB_OFF		0x400
22 #define LPC_LPT_MSB_OFF		0x404
23 #define LPC_LPT_START_OFF	0x408
24 
25 static struct st_clksrc_ddata {
26 	struct clk		*clk;
27 	void __iomem		*base;
28 } ddata;
29 
st_clksrc_reset(void)30 static void __init st_clksrc_reset(void)
31 {
32 	writel_relaxed(0, ddata.base + LPC_LPT_START_OFF);
33 	writel_relaxed(0, ddata.base + LPC_LPT_MSB_OFF);
34 	writel_relaxed(0, ddata.base + LPC_LPT_LSB_OFF);
35 	writel_relaxed(1, ddata.base + LPC_LPT_START_OFF);
36 }
37 
st_clksrc_sched_clock_read(void)38 static u64 notrace st_clksrc_sched_clock_read(void)
39 {
40 	return (u64)readl_relaxed(ddata.base + LPC_LPT_LSB_OFF);
41 }
42 
st_clksrc_init(void)43 static int __init st_clksrc_init(void)
44 {
45 	unsigned long rate;
46 	int ret;
47 
48 	st_clksrc_reset();
49 
50 	rate = clk_get_rate(ddata.clk);
51 
52 	sched_clock_register(st_clksrc_sched_clock_read, 32, rate);
53 
54 	ret = clocksource_mmio_init(ddata.base + LPC_LPT_LSB_OFF,
55 				    "clksrc-st-lpc", rate, 300, 32,
56 				    clocksource_mmio_readl_up);
57 	if (ret) {
58 		pr_err("clksrc-st-lpc: Failed to register clocksource\n");
59 		return ret;
60 	}
61 
62 	return 0;
63 }
64 
st_clksrc_setup_clk(struct device_node * np)65 static int __init st_clksrc_setup_clk(struct device_node *np)
66 {
67 	struct clk *clk;
68 
69 	clk = of_clk_get(np, 0);
70 	if (IS_ERR(clk)) {
71 		pr_err("clksrc-st-lpc: Failed to get LPC clock\n");
72 		return PTR_ERR(clk);
73 	}
74 
75 	if (clk_prepare_enable(clk)) {
76 		pr_err("clksrc-st-lpc: Failed to enable LPC clock\n");
77 		return -EINVAL;
78 	}
79 
80 	if (!clk_get_rate(clk)) {
81 		pr_err("clksrc-st-lpc: Failed to get LPC clock rate\n");
82 		clk_disable_unprepare(clk);
83 		return -EINVAL;
84 	}
85 
86 	ddata.clk = clk;
87 
88 	return 0;
89 }
90 
st_clksrc_of_register(struct device_node * np)91 static int __init st_clksrc_of_register(struct device_node *np)
92 {
93 	int ret;
94 	uint32_t mode;
95 
96 	ret = of_property_read_u32(np, "st,lpc-mode", &mode);
97 	if (ret) {
98 		pr_err("clksrc-st-lpc: An LPC mode must be provided\n");
99 		return ret;
100 	}
101 
102 	/* LPC can either run as a Clocksource or in RTC or WDT mode */
103 	if (mode != ST_LPC_MODE_CLKSRC)
104 		return 0;
105 
106 	ddata.base = of_iomap(np, 0);
107 	if (!ddata.base) {
108 		pr_err("clksrc-st-lpc: Unable to map iomem\n");
109 		return -ENXIO;
110 	}
111 
112 	ret = st_clksrc_setup_clk(np);
113 	if (ret) {
114 		iounmap(ddata.base);
115 		return ret;
116 	}
117 
118 	ret = st_clksrc_init();
119 	if (ret) {
120 		clk_disable_unprepare(ddata.clk);
121 		clk_put(ddata.clk);
122 		iounmap(ddata.base);
123 		return ret;
124 	}
125 
126 	pr_info("clksrc-st-lpc: clocksource initialised - running @ %luHz\n",
127 		clk_get_rate(ddata.clk));
128 
129 	return ret;
130 }
131 TIMER_OF_DECLARE(ddata, "st,stih407-lpc", st_clksrc_of_register);
132