1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Pistachio clocksource based on general-purpose timers
4 *
5 * Copyright (C) 2015 Imagination Technologies
6 */
7
8#define pr_fmt(fmt) "%s: " fmt, __func__
9
10#include <linux/clk.h>
11#include <linux/clocksource.h>
12#include <linux/clockchips.h>
13#include <linux/delay.h>
14#include <linux/err.h>
15#include <linux/init.h>
16#include <linux/spinlock.h>
17#include <linux/mfd/syscon.h>
18#include <linux/of.h>
19#include <linux/of_address.h>
20#include <linux/platform_device.h>
21#include <linux/regmap.h>
22#include <linux/sched_clock.h>
23#include <linux/time.h>
24
25/* Top level reg */
26#define CR_TIMER_CTRL_CFG 0x00
27#define TIMER_ME_GLOBAL BIT(0)
28#define CR_TIMER_REV 0x10
29
30/* Timer specific registers */
31#define TIMER_CFG 0x20
32#define TIMER_ME_LOCAL BIT(0)
33#define TIMER_RELOAD_VALUE 0x24
34#define TIMER_CURRENT_VALUE 0x28
35#define TIMER_CURRENT_OVERFLOW_VALUE 0x2C
36#define TIMER_IRQ_STATUS 0x30
37#define TIMER_IRQ_CLEAR 0x34
38#define TIMER_IRQ_MASK 0x38
39
40#define PERIP_TIMER_CONTROL 0x90
41
42/* Timer specific configuration Values */
43#define RELOAD_VALUE 0xffffffff
44
45struct pistachio_clocksource {
46 void __iomem *base;
47 raw_spinlock_t lock;
48 struct clocksource cs;
49};
50
51static struct pistachio_clocksource pcs_gpt;
52
53#define to_pistachio_clocksource(cs) \
54 container_of(cs, struct pistachio_clocksource, cs)
55
56static inline u32 gpt_readl(void __iomem *base, u32 offset, u32 gpt_id)
57{
58 return readl(addr: base + 0x20 * gpt_id + offset);
59}
60
61static inline void gpt_writel(void __iomem *base, u32 value, u32 offset,
62 u32 gpt_id)
63{
64 writel(val: value, addr: base + 0x20 * gpt_id + offset);
65}
66
67static u64 notrace
68pistachio_clocksource_read_cycles(struct clocksource *cs)
69{
70 struct pistachio_clocksource *pcs = to_pistachio_clocksource(cs);
71 __maybe_unused u32 overflow;
72 u32 counter;
73 unsigned long flags;
74
75 /*
76 * The counter value is only refreshed after the overflow value is read.
77 * And they must be read in strict order, hence raw spin lock added.
78 */
79
80 raw_spin_lock_irqsave(&pcs->lock, flags);
81 overflow = gpt_readl(base: pcs->base, TIMER_CURRENT_OVERFLOW_VALUE, gpt_id: 0);
82 counter = gpt_readl(base: pcs->base, TIMER_CURRENT_VALUE, gpt_id: 0);
83 raw_spin_unlock_irqrestore(&pcs->lock, flags);
84
85 return (u64)~counter;
86}
87
88static u64 notrace pistachio_read_sched_clock(void)
89{
90 return pistachio_clocksource_read_cycles(cs: &pcs_gpt.cs);
91}
92
93static void pistachio_clksrc_set_mode(struct clocksource *cs, int timeridx,
94 int enable)
95{
96 struct pistachio_clocksource *pcs = to_pistachio_clocksource(cs);
97 u32 val;
98
99 val = gpt_readl(base: pcs->base, TIMER_CFG, gpt_id: timeridx);
100 if (enable)
101 val |= TIMER_ME_LOCAL;
102 else
103 val &= ~TIMER_ME_LOCAL;
104
105 gpt_writel(base: pcs->base, value: val, TIMER_CFG, gpt_id: timeridx);
106}
107
108static void pistachio_clksrc_enable(struct clocksource *cs, int timeridx)
109{
110 struct pistachio_clocksource *pcs = to_pistachio_clocksource(cs);
111
112 /* Disable GPT local before loading reload value */
113 pistachio_clksrc_set_mode(cs, timeridx, enable: false);
114 gpt_writel(base: pcs->base, RELOAD_VALUE, TIMER_RELOAD_VALUE, gpt_id: timeridx);
115 pistachio_clksrc_set_mode(cs, timeridx, enable: true);
116}
117
118static void pistachio_clksrc_disable(struct clocksource *cs, int timeridx)
119{
120 /* Disable GPT local */
121 pistachio_clksrc_set_mode(cs, timeridx, enable: false);
122}
123
124static int pistachio_clocksource_enable(struct clocksource *cs)
125{
126 pistachio_clksrc_enable(cs, timeridx: 0);
127 return 0;
128}
129
130static void pistachio_clocksource_disable(struct clocksource *cs)
131{
132 pistachio_clksrc_disable(cs, timeridx: 0);
133}
134
135/* Desirable clock source for pistachio platform */
136static struct pistachio_clocksource pcs_gpt = {
137 .cs = {
138 .name = "gptimer",
139 .rating = 300,
140 .enable = pistachio_clocksource_enable,
141 .disable = pistachio_clocksource_disable,
142 .read = pistachio_clocksource_read_cycles,
143 .mask = CLOCKSOURCE_MASK(32),
144 .flags = CLOCK_SOURCE_IS_CONTINUOUS |
145 CLOCK_SOURCE_SUSPEND_NONSTOP,
146 },
147};
148
149static int __init pistachio_clksrc_of_init(struct device_node *node)
150{
151 struct clk *sys_clk, *fast_clk;
152 struct regmap *periph_regs;
153 unsigned long rate;
154 int ret;
155
156 pcs_gpt.base = of_iomap(node, index: 0);
157 if (!pcs_gpt.base) {
158 pr_err("cannot iomap\n");
159 return -ENXIO;
160 }
161
162 periph_regs = syscon_regmap_lookup_by_phandle(np: node, property: "img,cr-periph");
163 if (IS_ERR(ptr: periph_regs)) {
164 pr_err("cannot get peripheral regmap (%ld)\n",
165 PTR_ERR(periph_regs));
166 return PTR_ERR(ptr: periph_regs);
167 }
168
169 /* Switch to using the fast counter clock */
170 ret = regmap_update_bits(map: periph_regs, PERIP_TIMER_CONTROL,
171 mask: 0xf, val: 0x0);
172 if (ret)
173 return ret;
174
175 sys_clk = of_clk_get_by_name(np: node, name: "sys");
176 if (IS_ERR(ptr: sys_clk)) {
177 pr_err("clock get failed (%ld)\n", PTR_ERR(sys_clk));
178 return PTR_ERR(ptr: sys_clk);
179 }
180
181 fast_clk = of_clk_get_by_name(np: node, name: "fast");
182 if (IS_ERR(ptr: fast_clk)) {
183 pr_err("clock get failed (%lu)\n", PTR_ERR(fast_clk));
184 return PTR_ERR(ptr: fast_clk);
185 }
186
187 ret = clk_prepare_enable(clk: sys_clk);
188 if (ret < 0) {
189 pr_err("failed to enable clock (%d)\n", ret);
190 return ret;
191 }
192
193 ret = clk_prepare_enable(clk: fast_clk);
194 if (ret < 0) {
195 pr_err("failed to enable clock (%d)\n", ret);
196 clk_disable_unprepare(clk: sys_clk);
197 return ret;
198 }
199
200 rate = clk_get_rate(clk: fast_clk);
201
202 /* Disable irq's for clocksource usage */
203 gpt_writel(base: pcs_gpt.base, value: 0, TIMER_IRQ_MASK, gpt_id: 0);
204 gpt_writel(base: pcs_gpt.base, value: 0, TIMER_IRQ_MASK, gpt_id: 1);
205 gpt_writel(base: pcs_gpt.base, value: 0, TIMER_IRQ_MASK, gpt_id: 2);
206 gpt_writel(base: pcs_gpt.base, value: 0, TIMER_IRQ_MASK, gpt_id: 3);
207
208 /* Enable timer block */
209 writel(TIMER_ME_GLOBAL, addr: pcs_gpt.base);
210
211 raw_spin_lock_init(&pcs_gpt.lock);
212 sched_clock_register(read: pistachio_read_sched_clock, bits: 32, rate);
213 return clocksource_register_hz(cs: &pcs_gpt.cs, hz: rate);
214}
215TIMER_OF_DECLARE(pistachio_gptimer, "img,pistachio-gptimer",
216 pistachio_clksrc_of_init);
217

source code of linux/drivers/clocksource/timer-pistachio.c