#include <linux/platform_device.h>
#include <linux/ftrace.h>
-#include <asm/uaccess.h>
+#include <linux/uaccess.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <asm/page.h>
*/
irqreturn_t __irq_entry timer_interrupt(int irq, void *dev_id)
{
- unsigned long now, now2;
+ unsigned long now;
unsigned long next_tick;
- unsigned long cycles_elapsed, ticks_elapsed = 1;
- unsigned long cycles_remainder;
+ unsigned long ticks_elapsed = 0;
unsigned int cpu = smp_processor_id();
struct cpuinfo_parisc *cpuinfo = &per_cpu(cpu_data, cpu);
profile_tick(CPU_PROFILING);
- /* Initialize next_tick to the expected tick time. */
+ /* Initialize next_tick to the old expected tick time. */
next_tick = cpuinfo->it_value;
- /* Get current cycle counter (Control Register 16). */
- now = mfctl(16);
-
- cycles_elapsed = now - next_tick;
-
- if ((cycles_elapsed >> 6) < cpt) {
- /* use "cheap" math (add/subtract) instead
- * of the more expensive div/mul method
- */
- cycles_remainder = cycles_elapsed;
- while (cycles_remainder > cpt) {
- cycles_remainder -= cpt;
- ticks_elapsed++;
- }
- } else {
- /* TODO: Reduce this to one fdiv op */
- cycles_remainder = cycles_elapsed % cpt;
- ticks_elapsed += cycles_elapsed / cpt;
- }
-
- /* convert from "division remainder" to "remainder of clock tick" */
- cycles_remainder = cpt - cycles_remainder;
-
- /* Determine when (in CR16 cycles) next IT interrupt will fire.
- * We want IT to fire modulo clocktick even if we miss/skip some.
- * But those interrupts don't in fact get delivered that regularly.
- */
- next_tick = now + cycles_remainder;
+ /* Calculate how many ticks have elapsed. */
+ do {
+ ++ticks_elapsed;
+ next_tick += cpt;
+ now = mfctl(16);
+ } while (next_tick - now > cpt);
+ /* Store (in CR16 cycles) up to when we are accounting right now. */
cpuinfo->it_value = next_tick;
- /* Program the IT when to deliver the next interrupt.
- * Only bottom 32-bits of next_tick are writable in CR16!
- */
- mtctl(next_tick, 16);
+ /* Go do system house keeping. */
+ if (cpu == 0)
+ xtime_update(ticks_elapsed);
+
+ update_process_times(user_mode(get_irq_regs()));
- /* Skip one clocktick on purpose if we missed next_tick.
+ /* Skip clockticks on purpose if we know we would miss those.
* The new CR16 must be "later" than current CR16 otherwise
* itimer would not fire until CR16 wrapped - e.g 4 seconds
* later on a 1Ghz processor. We'll account for the missed
- * tick on the next timer interrupt.
+ * ticks on the next timer interrupt.
+ * We want IT to fire modulo clocktick even if we miss/skip some.
+ * But those interrupts don't in fact get delivered that regularly.
*
* "next_tick - now" will always give the difference regardless
* if one or the other wrapped. If "now" is "bigger" we'll end up
* with a very large unsigned number.
*/
- now2 = mfctl(16);
- if (next_tick - now2 > cpt)
- mtctl(next_tick+cpt, 16);
+ while (next_tick - mfctl(16) > cpt)
+ next_tick += cpt;
-#if 1
-/*
- * GGG: DEBUG code for how many cycles programming CR16 used.
- */
- if (unlikely(now2 - now > 0x3000)) /* 12K cycles */
- printk (KERN_CRIT "timer_interrupt(CPU %d): SLOW! 0x%lx cycles!"
- " cyc %lX rem %lX "
- " next/now %lX/%lX\n",
- cpu, now2 - now, cycles_elapsed, cycles_remainder,
- next_tick, now );
-#endif
-
- /* Can we differentiate between "early CR16" (aka Scenario 1) and
- * "long delay" (aka Scenario 3)? I don't think so.
- *
- * Timer_interrupt will be delivered at least a few hundred cycles
- * after the IT fires. But it's arbitrary how much time passes
- * before we call it "late". I've picked one second.
- *
- * It's important NO printk's are between reading CR16 and
- * setting up the next value. May introduce huge variance.
- */
- if (unlikely(ticks_elapsed > HZ)) {
- /* Scenario 3: very long delay? bad in any case */
- printk (KERN_CRIT "timer_interrupt(CPU %d): delayed!"
- " cycles %lX rem %lX "
- " next/now %lX/%lX\n",
- cpu,
- cycles_elapsed, cycles_remainder,
- next_tick, now );
- }
-
- /* Done mucking with unreliable delivery of interrupts.
- * Go do system house keeping.
+ /* Program the IT when to deliver the next interrupt.
+ * Only bottom 32-bits of next_tick are writable in CR16!
+ * Timer interrupt will be delivered at least a few hundred cycles
+ * after the IT fires, so if we are too close (<= 500 cycles) to the
+ * next cycle, simply skip it.
*/
-
- if (!--cpuinfo->prof_counter) {
- cpuinfo->prof_counter = cpuinfo->prof_multiplier;
- update_process_times(user_mode(get_irq_regs()));
- }
-
- if (cpu == 0)
- xtime_update(ticks_elapsed);
+ if (next_tick - mfctl(16) <= 500)
+ next_tick += cpt;
+ mtctl(next_tick, 16);
return IRQ_HANDLED;
}
projects / linux-2.6-block.git / blobdiff