From: john stultz Currently the i386 HPET code assumes the entire HPET implementation from the spec is present. This breaks on boxes that do not implement the optional legacy timer replacement functionality portion of the spec. This patch, which is very similar to my x86-64 patch for the same issue, fixes the problem allowing i386 systems that cannot use the HPET for the timer interrupt and RTC to still use the HPET as a time source. I've tested this patch on a system systems without HPET, with HPET but without legacy timer replacement, as well as HPET with legacy timer replacement. Signed-off-by: Andrew Morton --- arch/i386/kernel/time.c | 2 - arch/i386/kernel/time_hpet.c | 48 +++++++++++++++++++---------------- arch/i386/kernel/timers/timer_hpet.c | 11 +++++--- arch/i386/kernel/timers/timer_tsc.c | 2 - include/asm-i386/hpet.h | 1 5 files changed, 37 insertions(+), 27 deletions(-) diff -puN arch/i386/kernel/time.c~i386-fix-hpet-for-systems-that-dont-support arch/i386/kernel/time.c --- 25/arch/i386/kernel/time.c~i386-fix-hpet-for-systems-that-dont-support 2005-04-26 19:26:55.042480400 -0700 +++ 25-akpm/arch/i386/kernel/time.c 2005-04-26 19:26:55.053478728 -0700 @@ -441,7 +441,7 @@ static void __init hpet_time_init(void) set_normalized_timespec(&wall_to_monotonic, -xtime.tv_sec, -xtime.tv_nsec); - if (hpet_enable() >= 0) { + if ((hpet_enable() >= 0) && hpet_use_timer) { printk("Using HPET for base-timer\n"); } diff -puN arch/i386/kernel/time_hpet.c~i386-fix-hpet-for-systems-that-dont-support arch/i386/kernel/time_hpet.c --- 25/arch/i386/kernel/time_hpet.c~i386-fix-hpet-for-systems-that-dont-support 2005-04-26 19:26:55.043480248 -0700 +++ 25-akpm/arch/i386/kernel/time_hpet.c 2005-04-26 19:26:55.054478576 -0700 @@ -26,6 +26,7 @@ static unsigned long hpet_period; /* fsecs / HPET clock */ unsigned long hpet_tick; /* hpet clks count per tick */ unsigned long hpet_address; /* hpet memory map physical address */ +int hpet_use_timer; static int use_hpet; /* can be used for runtime check of hpet */ static int boot_hpet_disable; /* boottime override for HPET timer */ @@ -73,27 +74,30 @@ static int hpet_timer_stop_set_go(unsign hpet_writel(0, HPET_COUNTER); hpet_writel(0, HPET_COUNTER + 4); - /* - * Set up timer 0, as periodic with first interrupt to happen at - * hpet_tick, and period also hpet_tick. - */ - cfg = hpet_readl(HPET_T0_CFG); - cfg |= HPET_TN_ENABLE | HPET_TN_PERIODIC | - HPET_TN_SETVAL | HPET_TN_32BIT; - hpet_writel(cfg, HPET_T0_CFG); - - /* - * The first write after writing TN_SETVAL to the config register sets - * the counter value, the second write sets the threshold. - */ - hpet_writel(tick, HPET_T0_CMP); - hpet_writel(tick, HPET_T0_CMP); + if (hpet_use_timer) { + /* + * Set up timer 0, as periodic with first interrupt to happen at + * hpet_tick, and period also hpet_tick. + */ + cfg = hpet_readl(HPET_T0_CFG); + cfg |= HPET_TN_ENABLE | HPET_TN_PERIODIC | + HPET_TN_SETVAL | HPET_TN_32BIT; + hpet_writel(cfg, HPET_T0_CFG); + /* + * The first write after writing TN_SETVAL to the config register sets + * the counter value, the second write sets the threshold. + */ + hpet_writel(tick, HPET_T0_CMP); + hpet_writel(tick, HPET_T0_CMP); + } /* * Go! */ cfg = hpet_readl(HPET_CFG); - cfg |= HPET_CFG_ENABLE | HPET_CFG_LEGACY; + if (hpet_use_timer) + cfg |= HPET_CFG_LEGACY; + cfg |= HPET_CFG_ENABLE; hpet_writel(cfg, HPET_CFG); return 0; @@ -128,12 +132,11 @@ int __init hpet_enable(void) * However, we can do with one timer otherwise using the * the single HPET timer for system time. */ - if ( #ifdef CONFIG_HPET_EMULATE_RTC - !(id & HPET_ID_NUMBER) || -#endif - !(id & HPET_ID_LEGSUP)) + if (!(id & HPET_ID_NUMBER)) return -1; +#endif + hpet_period = hpet_readl(HPET_PERIOD); if ((hpet_period < HPET_MIN_PERIOD) || (hpet_period > HPET_MAX_PERIOD)) @@ -152,6 +155,8 @@ int __init hpet_enable(void) if (hpet_tick_rem > (hpet_period >> 1)) hpet_tick++; /* rounding the result */ + hpet_use_timer = id & HPET_ID_LEGSUP; + if (hpet_timer_stop_set_go(hpet_tick)) return -1; @@ -202,7 +207,8 @@ int __init hpet_enable(void) #endif #ifdef CONFIG_X86_LOCAL_APIC - wait_timer_tick = wait_hpet_tick; + if (hpet_use_timer) + wait_timer_tick = wait_hpet_tick; #endif return 0; } diff -puN arch/i386/kernel/timers/timer_hpet.c~i386-fix-hpet-for-systems-that-dont-support arch/i386/kernel/timers/timer_hpet.c --- 25/arch/i386/kernel/timers/timer_hpet.c~i386-fix-hpet-for-systems-that-dont-support 2005-04-26 19:26:55.045479944 -0700 +++ 25-akpm/arch/i386/kernel/timers/timer_hpet.c 2005-04-26 19:26:55.054478576 -0700 @@ -79,7 +79,7 @@ static unsigned long get_offset_hpet(voi eax = hpet_readl(HPET_COUNTER); eax -= hpet_last; /* hpet delta */ - + eax = min(hpet_tick, eax); /* * Time offset = (hpet delta) * ( usecs per HPET clock ) * = (hpet delta) * ( usecs per tick / HPET clocks per tick) @@ -105,9 +105,12 @@ static void mark_offset_hpet(void) last_offset = ((unsigned long long)last_tsc_high<<32)|last_tsc_low; rdtsc(last_tsc_low, last_tsc_high); - offset = hpet_readl(HPET_T0_CMP) - hpet_tick; - if (unlikely(((offset - hpet_last) > hpet_tick) && (hpet_last != 0))) { - int lost_ticks = (offset - hpet_last) / hpet_tick; + if (hpet_use_timer) + offset = hpet_readl(HPET_T0_CMP) - hpet_tick; + else + offset = hpet_readl(HPET_COUNTER); + if (unlikely(((offset - hpet_last) >= (2*hpet_tick)) && (hpet_last != 0))) { + int lost_ticks = ((offset - hpet_last) / hpet_tick) - 1; jiffies_64 += lost_ticks; } hpet_last = offset; diff -puN arch/i386/kernel/timers/timer_tsc.c~i386-fix-hpet-for-systems-that-dont-support arch/i386/kernel/timers/timer_tsc.c --- 25/arch/i386/kernel/timers/timer_tsc.c~i386-fix-hpet-for-systems-that-dont-support 2005-04-26 19:26:55.047479640 -0700 +++ 25-akpm/arch/i386/kernel/timers/timer_tsc.c 2005-04-26 19:26:55.055478424 -0700 @@ -497,7 +497,7 @@ static int __init init_tsc(char* overrid if (cpu_has_tsc) { unsigned long tsc_quotient; #ifdef CONFIG_HPET_TIMER - if (is_hpet_enabled()){ + if (is_hpet_enabled() && hpet_use_timer) { unsigned long result, remain; printk("Using TSC for gettimeofday\n"); tsc_quotient = calibrate_tsc_hpet(NULL); diff -puN include/asm-i386/hpet.h~i386-fix-hpet-for-systems-that-dont-support include/asm-i386/hpet.h --- 25/include/asm-i386/hpet.h~i386-fix-hpet-for-systems-that-dont-support 2005-04-26 19:26:55.049479336 -0700 +++ 25-akpm/include/asm-i386/hpet.h 2005-04-26 19:26:55.055478424 -0700 @@ -92,6 +92,7 @@ extern unsigned long hpet_tick; /* hpet clks count per tick */ extern unsigned long hpet_address; /* hpet memory map physical address */ +extern int hpet_use_timer; extern int hpet_rtc_timer_init(void); extern int hpet_enable(void); _