1 // SPDX-License-Identifier: GPL-2.0 1 // SPDX-License-Identifier: GPL-2.0
2 /* 2 /*
3 * 8253/PIT functions !! 3 * i8253.c 8253/PIT functions
4 * 4 *
5 */ 5 */
6 #include <linux/clockchips.h> 6 #include <linux/clockchips.h>
7 #include <linux/init.h> <<
8 #include <linux/timex.h> <<
9 #include <linux/i8253.h> 7 #include <linux/i8253.h>
>> 8 #include <linux/export.h>
>> 9 #include <linux/smp.h>
>> 10 #include <linux/irq.h>
10 11
11 #include <asm/hypervisor.h> <<
12 #include <asm/apic.h> <<
13 #include <asm/hpet.h> <<
14 #include <asm/time.h> 12 #include <asm/time.h>
15 #include <asm/smp.h> <<
16 13
17 /* !! 14 static irqreturn_t timer_interrupt(int irq, void *dev_id)
18 * HPET replaces the PIT, when enabled. So we <<
19 * the two timers is used <<
20 */ <<
21 struct clock_event_device *global_clock_event; <<
22 <<
23 /* <<
24 * Modern chipsets can disable the PIT clock w <<
25 * would be possible to enable the clock but t <<
26 * specific and not discoverable. Avoid the wh <<
27 * <<
28 * These platforms have discoverable TSC/CPU f <<
29 * requires to know the local APIC timer frequ <<
30 * calibrated against the PIT interrupt. <<
31 */ <<
32 static bool __init use_pit(void) <<
33 { 15 {
34 if (!IS_ENABLED(CONFIG_X86_TSC) || !bo !! 16 i8253_clockevent.event_handler(&i8253_clockevent);
35 return true; <<
36 17
37 /* This also returns true when APIC is !! 18 return IRQ_HANDLED;
38 return apic_needs_pit(); <<
39 } 19 }
40 20
41 bool __init pit_timer_init(void) !! 21 void __init setup_pit_timer(void)
42 { 22 {
43 if (!use_pit()) { !! 23 unsigned long flags = IRQF_NOBALANCING | IRQF_TIMER;
44 /* !! 24
45 * Don't just ignore the PIT. <<
46 * VMMs otherwise steal CPU ti <<
47 * the (masked) IRQ. <<
48 */ <<
49 clockevent_i8253_disable(); <<
50 return false; <<
51 } <<
52 clockevent_i8253_init(true); 25 clockevent_i8253_init(true);
53 global_clock_event = &i8253_clockevent !! 26 if (request_irq(0, timer_interrupt, flags, "timer", NULL))
54 return true; !! 27 pr_err("Failed to request irq 0 (timer)\n");
55 } 28 }
56 29
57 #ifndef CONFIG_X86_64 <<
58 static int __init init_pit_clocksource(void) 30 static int __init init_pit_clocksource(void)
59 { 31 {
60 /* !! 32 if (num_possible_cpus() > 1 || /* PIT does not scale! */
61 * Several reasons not to register PI <<
62 * <<
63 * - On SMP PIT does not scale due to <<
64 * - when HPET is enabled <<
65 * - when local APIC timer is active <<
66 */ <<
67 if (num_possible_cpus() > 1 || is_hpet <<
68 !clockevent_state_periodic(&i8253_ 33 !clockevent_state_periodic(&i8253_clockevent))
69 return 0; 34 return 0;
70 35
71 return clocksource_i8253_init(); 36 return clocksource_i8253_init();
72 } 37 }
73 arch_initcall(init_pit_clocksource); 38 arch_initcall(init_pit_clocksource);
74 #endif /* !CONFIG_X86_64 */ <<
75 39
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.