SMP - Single shot local timer

- APIC timer always reprogrammed if expired

- timer tick never happens when in kernel => never immediate return
  from userspace to kernel because of a buffered interrupt

- renamed argument to lapic_set_timer_one_shot()

- removed arch_ prefix from timer functions

kernel/arch/i386/apic.c

@@ -499,7 +499,7 @@ PRIVATE void apic_calibrate_clocks(unsigned cpu)
 	BOOT_VERBOSE(cpu_print_freq(cpuid));
 }
 
-PUBLIC void lapic_set_timer_one_shot(const u32_t value)
+PUBLIC void lapic_set_timer_one_shot(const u32_t usec)
 {
 	/* sleep in micro seconds */
 	u32_t lvtt;
@@ -508,7 +508,6 @@ PUBLIC void lapic_set_timer_one_shot(const u32_t value)
 
 	ticks_per_us = lapic_bus_freq[cpu] / 1000000;
 
-	/* calculate divisor and count from value */
 	lvtt = APIC_TDCR_1;
 	lapic_write(LAPIC_TIMER_DCR, lvtt);
 
@@ -516,7 +515,7 @@ PUBLIC void lapic_set_timer_one_shot(const u32_t value)
 	lvtt = APIC_TIMER_INT_VECTOR;
 	lapic_write(LAPIC_LVTTR, lvtt);
 
-	lapic_write(LAPIC_TIMER_ICR, value * ticks_per_us);
+	lapic_write(LAPIC_TIMER_ICR, usec * ticks_per_us);
 }
 
 PUBLIC void lapic_set_timer_periodic(const unsigned freq)
@@ -543,13 +542,16 @@ PUBLIC void lapic_stop_timer(void)
 	u32_t lvtt;
 	lvtt = lapic_read(LAPIC_LVTTR);
 	lapic_write(LAPIC_LVTTR, lvtt | APIC_LVTT_MASK);
+	/* zero the current counter so it can be restarted again */
+	lapic_write(LAPIC_TIMER_ICR, 0);
+	lapic_write(LAPIC_TIMER_CCR, 0);
 }
 
 PUBLIC void lapic_restart_timer(void)
 {
-	u32_t lvtt;
-	lvtt = lapic_read(LAPIC_LVTTR);
-	lapic_write(LAPIC_LVTTR, lvtt & ~APIC_LVTT_MASK);
+	/* restart the timer only if the counter reached zero, i.e. expired */
+	if (lapic_read(LAPIC_TIMER_CCR) == 0)
+		lapic_set_timer_one_shot(1000000/system_hz);
 }
 
 PUBLIC void lapic_microsec_sleep(unsigned count)

kernel/arch/i386/arch_clock.c

@@ -117,7 +117,7 @@ PRIVATE void estimate_cpu_freq(void)
 	BOOT_VERBOSE(cpu_print_freq(cpuid));
 }
 
-PUBLIC int arch_init_local_timer(unsigned freq)
+PUBLIC int init_local_timer(unsigned freq)
 {
 #ifdef CONFIG_APIC
 	/* if we know the address, lapic is enabled and we should use it */
@@ -140,7 +140,7 @@ PUBLIC int arch_init_local_timer(unsigned freq)
 	return 0;
 }
 
-PUBLIC void arch_stop_local_timer(void)
+PUBLIC void stop_local_timer(void)
 {
 #ifdef CONFIG_APIC
 	if (lapic_addr) {
@@ -153,19 +153,16 @@ PUBLIC void arch_stop_local_timer(void)
 	}
 }
 
-PUBLIC void arch_restart_local_timer(void)
+PUBLIC void restart_local_timer(void)
 {
 #ifdef CONFIG_APIC
 	if (lapic_addr) {
 		lapic_restart_timer();
-	} else
-#endif
-	{
-		init_8253A_timer(system_hz);
 	}
+#endif
 }
 
-PUBLIC int arch_register_local_timer_handler(const irq_handler_t handler)
+PUBLIC int register_local_timer_handler(const irq_handler_t handler)
 {
 #ifdef CONFIG_APIC
 	if (lapic_addr) {
@@ -269,7 +266,7 @@ PUBLIC void context_stop_idle(void)
 	context_stop(get_cpulocal_var_ptr(idle_proc));
 
 	if (is_idle)
-		arch_restart_local_timer();
+		restart_local_timer();
 }
 
 PUBLIC u64_t ms_2_cpu_time(unsigned ms)

kernel/arch/i386/arch_smp.c

@@ -238,7 +238,6 @@ PRIVATE void ap_finish_booting(void)
 		panic("FATAL : failed to initialize timer interrupts CPU %d, "
 				"cannot continue without any clock source!", cpu);
 	}
-	printf("CPU %d local APIC timer is ticking\n", cpu);
 
 	/* FIXME assign CPU local idle structure */
 	get_cpulocal_var(proc_ptr) = get_cpulocal_var_ptr(idle_proc);

kernel/clock.c

@@ -224,10 +224,10 @@ PRIVATE void load_update(void)
 
 PUBLIC int boot_cpu_init_timer(unsigned freq)
 {
-	if (arch_init_local_timer(freq))
+	if (init_local_timer(freq))
 		return -1;
 
-	if (arch_register_local_timer_handler(
+	if (register_local_timer_handler(
 				(irq_handler_t) timer_int_handler))
 		return -1;
 
@@ -236,6 +236,6 @@ PUBLIC int boot_cpu_init_timer(unsigned freq)
 
 PUBLIC int app_cpu_init_timer(unsigned freq)
 {
-	if (arch_init_local_timer(freq))
+	if (init_local_timer(freq))
 		return -1;
 }

kernel/clock.h

@@ -9,12 +9,12 @@ _PROTOTYPE(int app_cpu_init_timer, (unsigned freq));
 
 _PROTOTYPE(int timer_int_handler, (void));
 
-_PROTOTYPE(int arch_init_local_timer, (unsigned freq));
+_PROTOTYPE(int init_local_timer, (unsigned freq));
 /* sto p the local timer ticking */
-_PROTOTYPE(void arch_stop_local_timer, (void));
+_PROTOTYPE(void stop_local_timer, (void));
 /* let the time tick again with the original settings after it was stopped */
-_PROTOTYPE(void arch_restart_local_timer, (void));
-_PROTOTYPE(int arch_register_local_timer_handler, (irq_handler_t handler));
+_PROTOTYPE(void restart_local_timer, (void));
+_PROTOTYPE(int register_local_timer_handler, (irq_handler_t handler));
 
 _PROTOTYPE( u64_t ms_2_cpu_time, (unsigned ms));
 

kernel/main.c

@@ -376,8 +376,8 @@ PUBLIC void minix_shutdown(timer_t *tp)
   if (ncpus > 1)
 	  smp_shutdown_aps();
 #endif
-  arch_stop_local_timer();
   hw_intr_disable_all();
+  stop_local_timer();
   intr_init(INTS_ORIG, 0);
   arch_shutdown(tp ? tmr_arg(tp)->ta_int : RBT_PANIC);
 }

kernel/proc.c

@@ -191,7 +191,7 @@ PRIVATE void idle(void)
 #ifdef CONFIG_SMP
 	/* we don't need to keep time on APs as it is handled on the BSP */
 	if (cpuid != bsp_cpu_id)
-		arch_stop_local_timer();
+		stop_local_timer();
 	get_cpulocal_var(cpu_is_idle) = 1;
 #endif
 
@@ -338,10 +338,11 @@ check_misc_flags:
 	p->p_schedules++;
 #endif
 
-
 	p = arch_finish_switch_to_user();
 	assert(!is_zero64(p->p_cpu_time_left));
 
+	restart_local_timer();
+	
 	context_stop(proc_addr(KERNEL));
 
 	/* If the process isn't the owner of FPU, enable the FPU exception */

kernel/smp.c

@@ -30,7 +30,7 @@ PUBLIC void ap_boot_finished(unsigned cpu)
 PUBLIC void smp_ipi_halt_handler(void)
 {
 	ipi_ack();
-	arch_stop_local_timer();
+	stop_local_timer();
 	arch_smp_halt_cpu();
 }