Messages in this thread Patch in this message | | | Date | Mon, 09 Jan 2006 16:43:50 +0100 | From | Clemens Ladisch <> | Subject | [PATCH] HPET RTC emulation: add watchdog timer |
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To prevent the emulated RTC timer from stopping when interrupts are disabled for too long, implement the watchdog timer to restart it when needed.
Index: linux-2.6.15/arch/i386/kernel/time_hpet.c =================================================================== --- linux-2.6.15.orig/arch/i386/kernel/time_hpet.c 2006-01-06 16:11:10.000000000 +0100 +++ linux-2.6.15/arch/i386/kernel/time_hpet.c 2006-01-08 21:31:55.000000000 +0100 @@ -413,9 +413,45 @@ int hpet_set_periodic_freq(unsigned long int hpet_rtc_dropped_irq(void) { + unsigned int cnt, ticks_per_int, lost_ints; + if (!is_hpet_enabled()) return 0; + if (UIE_on | PIE_on | AIE_on) { + /* + * The interrupt handler schedules the next interrupt at a + * constant offset from the time the current interrupt was + * scheduled, without regard to the actual time. When the + * handler is delayed too long, it tries to schedule the next + * interrupt in the past and the hardware would not interrupt + * until the counter had wrapped around. We catch it here. + */ + cnt = hpet_readl(HPET_COUNTER); + /* was the comparator set to a time in the past? */ + if ((int)(cnt - hpet_t1_cmp) > 0) { + /* determine how many interrupts were actually lost */ + ticks_per_int = (hpet_tick * HZ) / hpet_rtc_int_freq; + lost_ints = (cnt - hpet_t1_cmp) / ticks_per_int + 1; + /* + * Make sure that, even with the time needed to execute + * this code, the next scheduled interrupt has been + * moved back to the future. + */ + lost_ints++; + + cnt = hpet_t1_cmp + lost_ints * ticks_per_int; + hpet_writel(cnt, HPET_T1_CMP); + hpet_t1_cmp = cnt; + + if (PIE_on) + PIE_count += lost_ints; + + printk(KERN_WARNING "rtc: lost some interrupts" + " at %ldHz.\n", hpet_rtc_int_freq); + } + } + return 1; } Index: linux-2.6.15/arch/x86_64/kernel/time.c =================================================================== --- linux-2.6.15.orig/arch/x86_64/kernel/time.c 2006-01-06 16:11:13.000000000 +0100 +++ linux-2.6.15/arch/x86_64/kernel/time.c 2006-01-08 21:42:16.000000000 +0100 @@ -1234,9 +1234,45 @@ int hpet_set_periodic_freq(unsigned long int hpet_rtc_dropped_irq(void) { + unsigned int cnt, ticks_per_int, lost_ints; + if (!is_hpet_enabled()) return 0; + if (UIE_on | PIE_on | AIE_on) { + /* + * The interrupt handler schedules the next interrupt at a + * constant offset from the time the current interrupt was + * scheduled, without regard to the actual time. When the + * handler is delayed too long, it tries to schedule the next + * interrupt in the past and the hardware would not interrupt + * until the counter had wrapped around. We catch it here. + */ + cnt = hpet_readl(HPET_COUNTER); + /* was the comparator set to a time in the past? */ + if ((int)(cnt - hpet_t1_cmp) > 0) { + /* determine how many interrupts were actually lost */ + ticks_per_int = (hpet_tick * HZ) / hpet_rtc_int_freq; + lost_ints = (cnt - hpet_t1_cmp) / ticks_per_int + 1; + /* + * Make sure that, even with the time needed to execute + * this code, the next scheduled interrupt has been + * moved back to the future. + */ + lost_ints++; + + cnt = hpet_t1_cmp + lost_ints * ticks_per_int; + hpet_writel(cnt, HPET_T1_CMP); + hpet_t1_cmp = cnt; + + if (PIE_on) + PIE_count += lost_ints; + + printk(KERN_WARNING "rtc: lost some interrupts" + " at %ldHz.\n", hpet_rtc_int_freq); + } + } + return 1; } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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