xref: /openbmc/qemu/hw/openrisc/cputimer.c (revision 6683d7bc)
1 /*
2  * QEMU OpenRISC timer support
3  *
4  * Copyright (c) 2011-2012 Jia Liu <proljc@gmail.com>
5  *                         Zhizhou Zhang <etouzh@gmail.com>
6  *
7  * This library is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2 of the License, or (at your option) any later version.
11  *
12  * This library is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
19  */
20 
21 #include "cpu.h"
22 #include "hw/hw.h"
23 #include "qemu/timer.h"
24 
25 #define TIMER_FREQ    (20 * 1000 * 1000)    /* 20MHz */
26 
27 /* The time when TTCR changes */
28 static uint64_t last_clk;
29 static int is_counting;
30 
31 void cpu_openrisc_count_update(OpenRISCCPU *cpu)
32 {
33     uint64_t now, next;
34     uint32_t wait;
35 
36     now = qemu_get_clock_ns(vm_clock);
37     if (!is_counting) {
38         qemu_del_timer(cpu->env.timer);
39         last_clk = now;
40         return;
41     }
42 
43     cpu->env.ttcr += (uint32_t)muldiv64(now - last_clk, TIMER_FREQ,
44                                         get_ticks_per_sec());
45     last_clk = now;
46 
47     if ((cpu->env.ttmr & TTMR_TP) <= (cpu->env.ttcr & TTMR_TP)) {
48         wait = TTMR_TP - (cpu->env.ttcr & TTMR_TP) + 1;
49         wait += cpu->env.ttmr & TTMR_TP;
50     } else {
51         wait = (cpu->env.ttmr & TTMR_TP) - (cpu->env.ttcr & TTMR_TP);
52     }
53 
54     next = now + muldiv64(wait, get_ticks_per_sec(), TIMER_FREQ);
55     qemu_mod_timer(cpu->env.timer, next);
56 }
57 
58 void cpu_openrisc_count_start(OpenRISCCPU *cpu)
59 {
60     is_counting = 1;
61     cpu_openrisc_count_update(cpu);
62 }
63 
64 void cpu_openrisc_count_stop(OpenRISCCPU *cpu)
65 {
66     is_counting = 0;
67     cpu_openrisc_count_update(cpu);
68 }
69 
70 static void openrisc_timer_cb(void *opaque)
71 {
72     OpenRISCCPU *cpu = opaque;
73 
74     if ((cpu->env.ttmr & TTMR_IE) &&
75          qemu_timer_expired(cpu->env.timer, qemu_get_clock_ns(vm_clock))) {
76         CPUState *cs = CPU(cpu);
77 
78         cpu->env.ttmr |= TTMR_IP;
79         cs->interrupt_request |= CPU_INTERRUPT_TIMER;
80     }
81 
82     switch (cpu->env.ttmr & TTMR_M) {
83     case TIMER_NONE:
84         break;
85     case TIMER_INTR:
86         cpu->env.ttcr = 0;
87         cpu_openrisc_count_start(cpu);
88         break;
89     case TIMER_SHOT:
90         cpu_openrisc_count_stop(cpu);
91         break;
92     case TIMER_CONT:
93         cpu_openrisc_count_start(cpu);
94         break;
95     }
96 }
97 
98 void cpu_openrisc_clock_init(OpenRISCCPU *cpu)
99 {
100     cpu->env.timer = qemu_new_timer_ns(vm_clock, &openrisc_timer_cb, cpu);
101     cpu->env.ttmr = 0x00000000;
102     cpu->env.ttcr = 0x00000000;
103 }
104