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kernel/x86: Avoid using any initial values in APIC timer registers.

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We should just be zeroing any unknown bits, not trying to preserve them.
If the BIOS or other mechanisms left the timer in some other mode
besides "one-shot" like we need, then we might incorrectly preserve
those bits.

This also has the advantage of avoiding config reads in set_hardware_timer.
This commit is contained in:
Augustin Cavalier
2026-05-21 15:01:17 -04:00
parent faa27a36dd
commit 5dfc0663d5
2 changed files with 29 additions and 38 deletions
Download Patch File Download Diff File Expand all files Collapse all files
headers/private/kernel/arch/x86/apic.h
-3
View File
@@ -68,9 +68,6 @@
/* Local Vector Table defines */
#define APIC_LVT_MASKED (1 << 16)
// timer defines
#define APIC_LVT_TIMER_MASK 0xfffcef00
// LINT0/1 defines
#define APIC_LVT_LINT_MASK 0xfffe0800
#define APIC_LVT_LINT_INPUT_POLARITY (1 << 13)
src/system/kernel/arch/x86/timers/x86_apic.cpp
+29 -35
View File
@@ -1,5 +1,5 @@
/*
* Copyright 2025, Haiku, Inc. All rights reserved.
* Copyright 2025-2026, Haiku, Inc. All rights reserved.
* Copyright 2008, Dustin Howett, [email protected]. All rights reserved.
* Copyright 2002-2010, Axel Dörfler, [email protected]. All rights reserved.
* Distributed under the terms of the MIT License.
@@ -28,21 +28,8 @@
#endif
/* Method Prototypes */
static int apic_timer_get_priority();
static status_t apic_timer_set_hardware_timer(bigtime_t relativeTimeout);
static status_t apic_timer_clear_hardware_timer();
static status_t apic_timer_init(struct kernel_args *args);
static uint32 sApicTicsPerSec = 0;
struct timer_info gAPICTimer = {
"APIC",
&apic_timer_get_priority,
&apic_timer_set_hardware_timer,
&apic_timer_clear_hardware_timer,
&apic_timer_init
};
static uint32 sApicTimerConfigBase = 0;
static int
@@ -72,13 +59,13 @@ apic_timer_set_hardware_timer(bigtime_t relativeTimeout)
cpu_status state = disable_interrupts();
uint32 config = apic_lvt_timer() | APIC_LVT_MASKED; // mask the timer
apic_set_lvt_timer(config);
// mask the timer
apic_set_lvt_timer(sApicTimerConfigBase | APIC_LVT_MASKED);
apic_set_lvt_initial_timer_count(0); // zero out the timer
config &= ~APIC_LVT_MASKED; // unmask the timer
apic_set_lvt_timer(config);
// unmask the timer
apic_set_lvt_timer(sApicTimerConfigBase);
TRACE("arch_smp_set_apic_timer: config 0x%" B_PRIx32 ", timeout %" B_PRIdBIGTIME
", tics/sec %" B_PRIu32 ", tics %" B_PRId64 "\n", config, relativeTimeout,
@@ -97,11 +84,11 @@ apic_timer_clear_hardware_timer()
{
cpu_status state = disable_interrupts();
uint32 config = apic_lvt_timer() | APIC_LVT_MASKED;
// mask the timer
apic_set_lvt_timer(config);
// mask the timer
apic_set_lvt_timer(sApicTimerConfigBase | APIC_LVT_MASKED);
apic_set_lvt_initial_timer_count(0); // zero out the timer
// zero out the timer
apic_set_lvt_initial_timer_count(0);
restore_interrupts(state);
return B_OK;
@@ -115,13 +102,11 @@ static uint32
calculate_apic_timer_conversion_factor()
{
// setup the timer
uint32 config = apic_lvt_timer() & APIC_LVT_TIMER_MASK;
config |= APIC_LVT_MASKED;
uint32 config = APIC_LVT_MASKED;
// timer masked, vector 0
apic_set_lvt_timer(config);
config = (apic_lvt_timer_divide_config() & ~0xf);
apic_set_lvt_timer_divide_config(config | APIC_TIMER_DIVIDE_CONFIG_1);
apic_set_lvt_timer_divide_config(APIC_TIMER_DIVIDE_CONFIG_1);
// divide clock by one
apic_set_lvt_initial_timer_count(UINT32_MAX); // start the counter
@@ -181,6 +166,8 @@ apic_timer_init(struct kernel_args *args)
install_io_interrupt_handler(0xfb - ARCH_INTERRUPT_BASE,
&apic_timer_interrupt, NULL, B_NO_LOCK_VECTOR);
sApicTimerConfigBase = 0xfb; // one-shot mode, vector 0xfb
apic_timer_per_cpu_init(args, 0);
// will be called on non-boot CPUs by apic_per_cpu_init()
@@ -191,16 +178,23 @@ apic_timer_init(struct kernel_args *args)
status_t
apic_timer_per_cpu_init(struct kernel_args *args, int32 cpu)
{
/* setup timer */
uint32 config = apic_lvt_timer() & APIC_LVT_TIMER_MASK;
config |= 0xfb | APIC_LVT_MASKED; // vector 0xfb, timer masked
apic_set_lvt_timer(config);
// setup timer
apic_set_lvt_timer(sApicTimerConfigBase | APIC_LVT_MASKED);
apic_set_lvt_initial_timer_count(0); // zero out the clock
// zero out the clock
apic_set_lvt_initial_timer_count(0);
config = apic_lvt_timer_divide_config() & 0xfffffff0;
config |= APIC_TIMER_DIVIDE_CONFIG_1; // clock division by 1
apic_set_lvt_timer_divide_config(config);
// clock division by 1
apic_set_lvt_timer_divide_config(APIC_TIMER_DIVIDE_CONFIG_1);
return B_OK;
}
struct timer_info gAPICTimer = {
"APIC",
&apic_timer_get_priority,
&apic_timer_set_hardware_timer,
&apic_timer_clear_hardware_timer,
&apic_timer_init
};