tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1/*
2 * Copyright (C) 2005-2013 Imagination Technologies Ltd.
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License version 2 as
6 * published by the Free Software Foundation.
7 *
8 * This program is distributed in the hope that it will be useful,
9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 * GNU General Public License for more details.
12 *
13 * You should have received a copy of the GNU General Public License
14 * along with this program. If not, see <http://www.gnu.org/licenses/>.
15 *
16 *
17 * Support for Meta per-thread timers.
18 *
19 * Meta hardware threads have 2 timers. The background timer (TXTIMER) is used
20 * as a free-running time base (hz clocksource), and the interrupt timer
21 * (TXTIMERI) is used for the timer interrupt (clock event). Both counters
22 * traditionally count at approximately 1MHz.
23 */
24
25#include <clocksource/metag_generic.h>
26#include <linux/cpu.h>
27#include <linux/errno.h>
28#include <linux/sched.h>
29#include <linux/kernel.h>
30#include <linux/param.h>
31#include <linux/time.h>
32#include <linux/init.h>
33#include <linux/proc_fs.h>
34#include <linux/clocksource.h>
35#include <linux/clockchips.h>
36#include <linux/interrupt.h>
37
38#include <asm/clock.h>
39#include <asm/hwthread.h>
40#include <asm/core_reg.h>
41#include <asm/metag_mem.h>
42#include <asm/tbx.h>
43
44#define HARDWARE_FREQ 1000000 /* 1MHz */
45#define HARDWARE_DIV 1 /* divide by 1 = 1MHz clock */
46#define HARDWARE_TO_NS_SHIFT 10 /* convert ticks to ns */
47
48static unsigned int hwtimer_freq = HARDWARE_FREQ;
49static DEFINE_PER_CPU(struct clock_event_device, local_clockevent);
50static DEFINE_PER_CPU(char [11], local_clockevent_name);
51
52static int metag_timer_set_next_event(unsigned long delta,
53 struct clock_event_device *dev)
54{
55 __core_reg_set(TXTIMERI, -delta);
56 return 0;
57}
58
59static cycle_t metag_clocksource_read(struct clocksource *cs)
60{
61 return __core_reg_get(TXTIMER);
62}
63
64static struct clocksource clocksource_metag = {
65 .name = "META",
66 .rating = 200,
67 .mask = CLOCKSOURCE_MASK(32),
68 .read = metag_clocksource_read,
69 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
70};
71
72static irqreturn_t metag_timer_interrupt(int irq, void *dummy)
73{
74 struct clock_event_device *evt = this_cpu_ptr(&local_clockevent);
75
76 evt->event_handler(evt);
77
78 return IRQ_HANDLED;
79}
80
81static struct irqaction metag_timer_irq = {
82 .name = "META core timer",
83 .handler = metag_timer_interrupt,
84 .flags = IRQF_TIMER | IRQF_IRQPOLL | IRQF_PERCPU,
85};
86
87unsigned long long sched_clock(void)
88{
89 unsigned long long ticks = __core_reg_get(TXTIMER);
90 return ticks << HARDWARE_TO_NS_SHIFT;
91}
92
93static int arch_timer_starting_cpu(unsigned int cpu)
94{
95 unsigned int txdivtime;
96 struct clock_event_device *clk = &per_cpu(local_clockevent, cpu);
97 char *name = per_cpu(local_clockevent_name, cpu);
98
99 txdivtime = __core_reg_get(TXDIVTIME);
100
101 txdivtime &= ~TXDIVTIME_DIV_BITS;
102 txdivtime |= (HARDWARE_DIV & TXDIVTIME_DIV_BITS);
103
104 __core_reg_set(TXDIVTIME, txdivtime);
105
106 sprintf(name, "META %d", cpu);
107 clk->name = name;
108 clk->features = CLOCK_EVT_FEAT_ONESHOT,
109
110 clk->rating = 200,
111 clk->shift = 12,
112 clk->irq = tbisig_map(TBID_SIGNUM_TRT),
113 clk->set_next_event = metag_timer_set_next_event,
114
115 clk->mult = div_sc(hwtimer_freq, NSEC_PER_SEC, clk->shift);
116 clk->max_delta_ns = clockevent_delta2ns(0x7fffffff, clk);
117 clk->min_delta_ns = clockevent_delta2ns(0xf, clk);
118 clk->cpumask = cpumask_of(cpu);
119
120 clockevents_register_device(clk);
121
122 /*
123 * For all non-boot CPUs we need to synchronize our free
124 * running clock (TXTIMER) with the boot CPU's clock.
125 *
126 * While this won't be accurate, it should be close enough.
127 */
128 if (cpu) {
129 unsigned int thread0 = cpu_2_hwthread_id[0];
130 unsigned long val;
131
132 val = core_reg_read(TXUCT_ID, TXTIMER_REGNUM, thread0);
133 __core_reg_set(TXTIMER, val);
134 }
135 return 0;
136}
137
138int __init metag_generic_timer_init(void)
139{
140 /*
141 * On Meta 2 SoCs, the actual frequency of the timer is based on the
142 * Meta core clock speed divided by an integer, so it is only
143 * approximately 1MHz. Calculating the real frequency here drastically
144 * reduces clock skew on these SoCs.
145 */
146#ifdef CONFIG_METAG_META21
147 hwtimer_freq = get_coreclock() / (metag_in32(EXPAND_TIMER_DIV) + 1);
148#endif
149 pr_info("Timer frequency: %u Hz\n", hwtimer_freq);
150
151 clocksource_register_hz(&clocksource_metag, hwtimer_freq);
152
153 setup_irq(tbisig_map(TBID_SIGNUM_TRT), &metag_timer_irq);
154
155 /* Hook cpu boot to configure the CPU's timers */
156 return cpuhp_setup_state(CPUHP_AP_METAG_TIMER_STARTING,
157 "AP_METAG_TIMER_STARTING",
158 arch_timer_starting_cpu, NULL);
159}