1/*
2 * J-Core SoC PIT/clocksource driver
3 *
4 * Copyright (C) 2015-2016 Smart Energy Instruments, Inc.
5 *
6 * This file is subject to the terms and conditions of the GNU General Public
7 * License. See the file "COPYING" in the main directory of this archive
8 * for more details.
9 */
10
11#include <linux/kernel.h>
12#include <linux/slab.h>
13#include <linux/interrupt.h>
14#include <linux/clockchips.h>
15#include <linux/clocksource.h>
16#include <linux/sched_clock.h>
17#include <linux/cpu.h>
18#include <linux/cpuhotplug.h>
19#include <linux/of_address.h>
20#include <linux/of_irq.h>
21
22#define PIT_IRQ_SHIFT 12
23#define PIT_PRIO_SHIFT 20
24#define PIT_ENABLE_SHIFT 26
25#define PIT_PRIO_MASK 0xf
26
27#define REG_PITEN 0x00
28#define REG_THROT 0x10
29#define REG_COUNT 0x14
30#define REG_BUSPD 0x18
31#define REG_SECHI 0x20
32#define REG_SECLO 0x24
33#define REG_NSEC 0x28
34
35struct jcore_pit {
36 struct clock_event_device ced;
37 void __iomem *base;
38 unsigned long periodic_delta;
39 u32 enable_val;
40};
41
42static void __iomem *jcore_pit_base;
43static struct jcore_pit __percpu *jcore_pit_percpu;
44
45static notrace u64 jcore_sched_clock_read(void)
46{
47 u32 seclo, nsec, seclo0;
48 __iomem void *base = jcore_pit_base;
49
50 seclo = readl(base + REG_SECLO);
51 do {
52 seclo0 = seclo;
53 nsec = readl(base + REG_NSEC);
54 seclo = readl(base + REG_SECLO);
55 } while (seclo0 != seclo);
56
57 return seclo * NSEC_PER_SEC + nsec;
58}
59
60static u64 jcore_clocksource_read(struct clocksource *cs)
61{
62 return jcore_sched_clock_read();
63}
64
65static int jcore_pit_disable(struct jcore_pit *pit)
66{
67 writel(0, pit->base + REG_PITEN);
68 return 0;
69}
70
71static int jcore_pit_set(unsigned long delta, struct jcore_pit *pit)
72{
73 jcore_pit_disable(pit);
74 writel(delta, pit->base + REG_THROT);
75 writel(pit->enable_val, pit->base + REG_PITEN);
76 return 0;
77}
78
79static int jcore_pit_set_state_shutdown(struct clock_event_device *ced)
80{
81 struct jcore_pit *pit = container_of(ced, struct jcore_pit, ced);
82
83 return jcore_pit_disable(pit);
84}
85
86static int jcore_pit_set_state_oneshot(struct clock_event_device *ced)
87{
88 struct jcore_pit *pit = container_of(ced, struct jcore_pit, ced);
89
90 return jcore_pit_disable(pit);
91}
92
93static int jcore_pit_set_state_periodic(struct clock_event_device *ced)
94{
95 struct jcore_pit *pit = container_of(ced, struct jcore_pit, ced);
96
97 return jcore_pit_set(pit->periodic_delta, pit);
98}
99
100static int jcore_pit_set_next_event(unsigned long delta,
101 struct clock_event_device *ced)
102{
103 struct jcore_pit *pit = container_of(ced, struct jcore_pit, ced);
104
105 return jcore_pit_set(delta, pit);
106}
107
108static int jcore_pit_local_init(unsigned cpu)
109{
110 struct jcore_pit *pit = this_cpu_ptr(jcore_pit_percpu);
111 unsigned buspd, freq;
112
113 pr_info("Local J-Core PIT init on cpu %u\n", cpu);
114
115 buspd = readl(pit->base + REG_BUSPD);
116 freq = DIV_ROUND_CLOSEST(NSEC_PER_SEC, buspd);
117 pit->periodic_delta = DIV_ROUND_CLOSEST(NSEC_PER_SEC, HZ * buspd);
118
119 clockevents_config_and_register(&pit->ced, freq, 1, ULONG_MAX);
120
121 return 0;
122}
123
124static irqreturn_t jcore_timer_interrupt(int irq, void *dev_id)
125{
126 struct jcore_pit *pit = this_cpu_ptr(dev_id);
127
128 if (clockevent_state_oneshot(&pit->ced))
129 jcore_pit_disable(pit);
130
131 pit->ced.event_handler(&pit->ced);
132
133 return IRQ_HANDLED;
134}
135
136static int __init jcore_pit_init(struct device_node *node)
137{
138 int err;
139 unsigned pit_irq, cpu;
140 unsigned long hwirq;
141 u32 irqprio, enable_val;
142
143 jcore_pit_base = of_iomap(node, 0);
144 if (!jcore_pit_base) {
145 pr_err("Error: Cannot map base address for J-Core PIT\n");
146 return -ENXIO;
147 }
148
149 pit_irq = irq_of_parse_and_map(node, 0);
150 if (!pit_irq) {
151 pr_err("Error: J-Core PIT has no IRQ\n");
152 return -ENXIO;
153 }
154
155 pr_info("Initializing J-Core PIT at %p IRQ %d\n",
156 jcore_pit_base, pit_irq);
157
158 err = clocksource_mmio_init(jcore_pit_base, "jcore_pit_cs",
159 NSEC_PER_SEC, 400, 32,
160 jcore_clocksource_read);
161 if (err) {
162 pr_err("Error registering clocksource device: %d\n", err);
163 return err;
164 }
165
166 sched_clock_register(jcore_sched_clock_read, 32, NSEC_PER_SEC);
167
168 jcore_pit_percpu = alloc_percpu(struct jcore_pit);
169 if (!jcore_pit_percpu) {
170 pr_err("Failed to allocate memory for clock event device\n");
171 return -ENOMEM;
172 }
173
174 err = request_irq(pit_irq, jcore_timer_interrupt,
175 IRQF_TIMER | IRQF_PERCPU,
176 "jcore_pit", jcore_pit_percpu);
177 if (err) {
178 pr_err("pit irq request failed: %d\n", err);
179 free_percpu(jcore_pit_percpu);
180 return err;
181 }
182
183 /*
184 * The J-Core PIT is not hard-wired to a particular IRQ, but
185 * integrated with the interrupt controller such that the IRQ it
186 * generates is programmable, as follows:
187 *
188 * The bit layout of the PIT enable register is:
189 *
190 * .....e..ppppiiiiiiii............
191 *
192 * where the .'s indicate unrelated/unused bits, e is enable,
193 * p is priority, and i is hard irq number.
194 *
195 * For the PIT included in AIC1 (obsolete but still in use),
196 * any hard irq (trap number) can be programmed via the 8
197 * iiiiiiii bits, and a priority (0-15) is programmable
198 * separately in the pppp bits.
199 *
200 * For the PIT included in AIC2 (current), the programming
201 * interface is equivalent modulo interrupt mapping. This is
202 * why a different compatible tag was not used. However only
203 * traps 64-127 (the ones actually intended to be used for
204 * interrupts, rather than syscalls/exceptions/etc.) can be
205 * programmed (the high 2 bits of i are ignored) and the
206 * priority pppp is <<2'd and or'd onto the irq number. This
207 * choice seems to have been made on the hardware engineering
208 * side under an assumption that preserving old AIC1 priority
209 * mappings was important. Future models will likely ignore
210 * the pppp field.
211 */
212 hwirq = irq_get_irq_data(pit_irq)->hwirq;
213 irqprio = (hwirq >> 2) & PIT_PRIO_MASK;
214 enable_val = (1U << PIT_ENABLE_SHIFT)
215 | (hwirq << PIT_IRQ_SHIFT)
216 | (irqprio << PIT_PRIO_SHIFT);
217
218 for_each_present_cpu(cpu) {
219 struct jcore_pit *pit = per_cpu_ptr(jcore_pit_percpu, cpu);
220
221 pit->base = of_iomap(node, cpu);
222 if (!pit->base) {
223 pr_err("Unable to map PIT for cpu %u\n", cpu);
224 continue;
225 }
226
227 pit->ced.name = "jcore_pit";
228 pit->ced.features = CLOCK_EVT_FEAT_PERIODIC
229 | CLOCK_EVT_FEAT_ONESHOT
230 | CLOCK_EVT_FEAT_PERCPU;
231 pit->ced.cpumask = cpumask_of(cpu);
232 pit->ced.rating = 400;
233 pit->ced.irq = pit_irq;
234 pit->ced.set_state_shutdown = jcore_pit_set_state_shutdown;
235 pit->ced.set_state_periodic = jcore_pit_set_state_periodic;
236 pit->ced.set_state_oneshot = jcore_pit_set_state_oneshot;
237 pit->ced.set_next_event = jcore_pit_set_next_event;
238
239 pit->enable_val = enable_val;
240 }
241
242 cpuhp_setup_state(CPUHP_AP_JCORE_TIMER_STARTING,
243 "clockevents/jcore:starting",
244 jcore_pit_local_init, NULL);
245
246 return 0;
247}
248
249TIMER_OF_DECLARE(jcore_pit, "jcore,pit", jcore_pit_init);
250