summaryrefslogtreecommitdiff
path: root/drivers/clocksource/metag_generic.c
blob: 172f43d4bc1af073af4329723b1fe290b963e9b3 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
/*
 * Copyright (C) 2005-2013 Imagination Technologies Ltd.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *
 * Support for Meta per-thread timers.
 *
 * Meta hardware threads have 2 timers. The background timer (TXTIMER) is used
 * as a free-running time base (hz clocksource), and the interrupt timer
 * (TXTIMERI) is used for the timer interrupt (clock event). Both counters
 * traditionally count at approximately 1MHz.
 */

#include <clocksource/metag_generic.h>
#include <linux/cpu.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/param.h>
#include <linux/time.h>
#include <linux/init.h>
#include <linux/proc_fs.h>
#include <linux/clocksource.h>
#include <linux/clockchips.h>
#include <linux/interrupt.h>

#include <asm/clock.h>
#include <asm/hwthread.h>
#include <asm/core_reg.h>
#include <asm/metag_mem.h>
#include <asm/tbx.h>

#define HARDWARE_FREQ		1000000	/* 1MHz */
#define HARDWARE_DIV		1	/* divide by 1 = 1MHz clock */
#define HARDWARE_TO_NS_SHIFT	10	/* convert ticks to ns */

static unsigned int hwtimer_freq = HARDWARE_FREQ;
static DEFINE_PER_CPU(struct clock_event_device, local_clockevent);
static DEFINE_PER_CPU(char [11], local_clockevent_name);

static int metag_timer_set_next_event(unsigned long delta,
				      struct clock_event_device *dev)
{
	__core_reg_set(TXTIMERI, -delta);
	return 0;
}

static cycle_t metag_clocksource_read(struct clocksource *cs)
{
	return __core_reg_get(TXTIMER);
}

static struct clocksource clocksource_metag = {
	.name = "META",
	.rating = 200,
	.mask = CLOCKSOURCE_MASK(32),
	.read = metag_clocksource_read,
	.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};

static irqreturn_t metag_timer_interrupt(int irq, void *dummy)
{
	struct clock_event_device *evt = this_cpu_ptr(&local_clockevent);

	evt->event_handler(evt);

	return IRQ_HANDLED;
}

static struct irqaction metag_timer_irq = {
	.name = "META core timer",
	.handler = metag_timer_interrupt,
	.flags = IRQF_TIMER | IRQF_IRQPOLL | IRQF_PERCPU,
};

unsigned long long sched_clock(void)
{
	unsigned long long ticks = __core_reg_get(TXTIMER);
	return ticks << HARDWARE_TO_NS_SHIFT;
}

static int arch_timer_starting_cpu(unsigned int cpu)
{
	unsigned int txdivtime;
	struct clock_event_device *clk = &per_cpu(local_clockevent, cpu);
	char *name = per_cpu(local_clockevent_name, cpu);

	txdivtime = __core_reg_get(TXDIVTIME);

	txdivtime &= ~TXDIVTIME_DIV_BITS;
	txdivtime |= (HARDWARE_DIV & TXDIVTIME_DIV_BITS);

	__core_reg_set(TXDIVTIME, txdivtime);

	sprintf(name, "META %d", cpu);
	clk->name = name;
	clk->features = CLOCK_EVT_FEAT_ONESHOT,

	clk->rating = 200,
	clk->shift = 12,
	clk->irq = tbisig_map(TBID_SIGNUM_TRT),
	clk->set_next_event = metag_timer_set_next_event,

	clk->mult = div_sc(hwtimer_freq, NSEC_PER_SEC, clk->shift);
	clk->max_delta_ns = clockevent_delta2ns(0x7fffffff, clk);
	clk->min_delta_ns = clockevent_delta2ns(0xf, clk);
	clk->cpumask = cpumask_of(cpu);

	clockevents_register_device(clk);

	/*
	 * For all non-boot CPUs we need to synchronize our free
	 * running clock (TXTIMER) with the boot CPU's clock.
	 *
	 * While this won't be accurate, it should be close enough.
	 */
	if (cpu) {
		unsigned int thread0 = cpu_2_hwthread_id[0];
		unsigned long val;

		val = core_reg_read(TXUCT_ID, TXTIMER_REGNUM, thread0);
		__core_reg_set(TXTIMER, val);
	}
	return 0;
}

int __init metag_generic_timer_init(void)
{
	/*
	 * On Meta 2 SoCs, the actual frequency of the timer is based on the
	 * Meta core clock speed divided by an integer, so it is only
	 * approximately 1MHz. Calculating the real frequency here drastically
	 * reduces clock skew on these SoCs.
	 */
#ifdef CONFIG_METAG_META21
	hwtimer_freq = get_coreclock() / (metag_in32(EXPAND_TIMER_DIV) + 1);
#endif
	pr_info("Timer frequency: %u Hz\n", hwtimer_freq);

	clocksource_register_hz(&clocksource_metag, hwtimer_freq);

	setup_irq(tbisig_map(TBID_SIGNUM_TRT), &metag_timer_irq);

	/* Hook cpu boot to configure the CPU's timers */
	return cpuhp_setup_state(CPUHP_AP_METAG_TIMER_STARTING,
				 "clockevents/metag:starting",
				 arch_timer_starting_cpu, NULL);
}