From f00c96f313b07d2eb2845305b9a3395e14385767 Mon Sep 17 00:00:00 2001 From: Clemens Ladisch Date: Sun, 30 Oct 2005 15:03:35 -0800 Subject: [PATCH] hpet-RTC: disable interrupt when no longer needed When the emulated RTC interrupt is no longer needed, we better disable it; otherwise, we get a spurious interrupt whenever the timer has rolled over and reaches the same comparator value. Having a superfluous interrupt every five minutes doesn't hurt much, but it's bad style anyway. ;-) Signed-off-by: Clemens Ladisch Acked-by: "Pallipadi, Venkatesh" Cc: Andi Kleen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/i386/kernel/time_hpet.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'arch/i386/kernel/time_hpet.c') diff --git a/arch/i386/kernel/time_hpet.c b/arch/i386/kernel/time_hpet.c index 658c0629ba6..23e81fcbeae 100644 --- a/arch/i386/kernel/time_hpet.c +++ b/arch/i386/kernel/time_hpet.c @@ -319,8 +319,12 @@ static void hpet_rtc_timer_reinit(void) { unsigned int cfg, cnt; - if (!(PIE_on | AIE_on | UIE_on)) + if (unlikely(!(PIE_on | AIE_on | UIE_on))) { + cfg = hpet_readl(HPET_T1_CFG); + cfg &= ~HPET_TN_ENABLE; + hpet_writel(cfg, HPET_T1_CFG); return; + } if (PIE_on && (PIE_freq > DEFAULT_RTC_INT_FREQ)) hpet_rtc_int_freq = PIE_freq; -- cgit v1.2.3-70-g09d2 From 5f819949ee4e5a06c2e0054cbb42f3f0d170d779 Mon Sep 17 00:00:00 2001 From: Clemens Ladisch Date: Sun, 30 Oct 2005 15:03:36 -0800 Subject: [PATCH] hpet-RTC: fix timer config register accesses Make sure that the RTC timer is in non-periodic mode; some stupid BIOS might have initialized it to periodic mode. Furthermore, don't set the SETVAL bit in the config register. This wouldn't have any effect unless the timer was in period mode (which it isn't), and then the actual timer frequency would be half that of the desired one because incrementing the comparator in the interrupt handler would be done after the hardware has already incremented it itself. Signed-off-by: Clemens Ladisch Acked-by: Venkatesh Pallipadi Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/i386/kernel/time_hpet.c | 9 ++------- arch/x86_64/kernel/time.c | 9 ++------- 2 files changed, 4 insertions(+), 14 deletions(-) (limited to 'arch/i386/kernel/time_hpet.c') diff --git a/arch/i386/kernel/time_hpet.c b/arch/i386/kernel/time_hpet.c index 23e81fcbeae..cb1f313858e 100644 --- a/arch/i386/kernel/time_hpet.c +++ b/arch/i386/kernel/time_hpet.c @@ -309,7 +309,8 @@ int hpet_rtc_timer_init(void) local_irq_restore(flags); cfg = hpet_readl(HPET_T1_CFG); - cfg |= HPET_TN_ENABLE | HPET_TN_SETVAL | HPET_TN_32BIT; + cfg &= ~HPET_TN_PERIODIC; + cfg |= HPET_TN_ENABLE | HPET_TN_32BIT; hpet_writel(cfg, HPET_T1_CFG); return 1; @@ -335,12 +336,6 @@ static void hpet_rtc_timer_reinit(void) cnt = hpet_readl(HPET_T1_CMP); cnt += hpet_tick*HZ/hpet_rtc_int_freq; hpet_writel(cnt, HPET_T1_CMP); - - cfg = hpet_readl(HPET_T1_CFG); - cfg |= HPET_TN_ENABLE | HPET_TN_SETVAL | HPET_TN_32BIT; - hpet_writel(cfg, HPET_T1_CFG); - - return; } /* diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c index 7037ca668c6..35a896ef4c3 100644 --- a/arch/x86_64/kernel/time.c +++ b/arch/x86_64/kernel/time.c @@ -1128,7 +1128,8 @@ int hpet_rtc_timer_init(void) local_irq_restore(flags); cfg = hpet_readl(HPET_T1_CFG); - cfg |= HPET_TN_ENABLE | HPET_TN_SETVAL | HPET_TN_32BIT; + cfg &= ~HPET_TN_PERIODIC; + cfg |= HPET_TN_ENABLE | HPET_TN_32BIT; hpet_writel(cfg, HPET_T1_CFG); return 1; @@ -1154,12 +1155,6 @@ static void hpet_rtc_timer_reinit(void) cnt = hpet_readl(HPET_T1_CMP); cnt += hpet_tick*HZ/hpet_rtc_int_freq; hpet_writel(cnt, HPET_T1_CMP); - - cfg = hpet_readl(HPET_T1_CFG); - cfg |= HPET_TN_ENABLE | HPET_TN_SETVAL | HPET_TN_32BIT; - hpet_writel(cfg, HPET_T1_CFG); - - return; } /* -- cgit v1.2.3-70-g09d2 From 7811fb8f400a3dbfa027d86bb583a31c66fddfc3 Mon Sep 17 00:00:00 2001 From: Clemens Ladisch Date: Sun, 30 Oct 2005 15:03:36 -0800 Subject: [PATCH] hpet-RTC: cache the comparator register Reads from an HPET register require a round trip to the south bridge and are almost as slow as PCI reads. By caching the last value we've written to the comparator register, we can eliminate all HPET reads from the fast path in the emulated RTC interrupt handler. Signed-off-by: Clemens Ladisch Acked-by: Venkatesh Pallipadi Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/i386/kernel/time_hpet.c | 5 ++++- arch/x86_64/kernel/time.c | 5 ++++- 2 files changed, 8 insertions(+), 2 deletions(-) (limited to 'arch/i386/kernel/time_hpet.c') diff --git a/arch/i386/kernel/time_hpet.c b/arch/i386/kernel/time_hpet.c index cb1f313858e..9caeaa315cd 100644 --- a/arch/i386/kernel/time_hpet.c +++ b/arch/i386/kernel/time_hpet.c @@ -275,6 +275,7 @@ static unsigned long PIE_freq = DEFAULT_RTC_INT_FREQ; static unsigned long PIE_count; static unsigned long hpet_rtc_int_freq; /* RTC interrupt frequency */ +static unsigned int hpet_t1_cmp; /* cached comparator register */ /* * Timer 1 for RTC, we do not use periodic interrupt feature, @@ -306,6 +307,7 @@ int hpet_rtc_timer_init(void) cnt = hpet_readl(HPET_COUNTER); cnt += ((hpet_tick*HZ)/hpet_rtc_int_freq); hpet_writel(cnt, HPET_T1_CMP); + hpet_t1_cmp = cnt; local_irq_restore(flags); cfg = hpet_readl(HPET_T1_CFG); @@ -333,9 +335,10 @@ static void hpet_rtc_timer_reinit(void) hpet_rtc_int_freq = DEFAULT_RTC_INT_FREQ; /* It is more accurate to use the comparator value than current count.*/ - cnt = hpet_readl(HPET_T1_CMP); + cnt = hpet_t1_cmp; cnt += hpet_tick*HZ/hpet_rtc_int_freq; hpet_writel(cnt, HPET_T1_CMP); + hpet_t1_cmp = cnt; } /* diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c index 35a896ef4c3..fdaddc4e528 100644 --- a/arch/x86_64/kernel/time.c +++ b/arch/x86_64/kernel/time.c @@ -1089,6 +1089,7 @@ static unsigned long PIE_freq = DEFAULT_RTC_INT_FREQ; static unsigned long PIE_count; static unsigned long hpet_rtc_int_freq; /* RTC interrupt frequency */ +static unsigned int hpet_t1_cmp; /* cached comparator register */ int is_hpet_enabled(void) { @@ -1125,6 +1126,7 @@ int hpet_rtc_timer_init(void) cnt = hpet_readl(HPET_COUNTER); cnt += ((hpet_tick*HZ)/hpet_rtc_int_freq); hpet_writel(cnt, HPET_T1_CMP); + hpet_t1_cmp = cnt; local_irq_restore(flags); cfg = hpet_readl(HPET_T1_CFG); @@ -1152,9 +1154,10 @@ static void hpet_rtc_timer_reinit(void) hpet_rtc_int_freq = DEFAULT_RTC_INT_FREQ; /* It is more accurate to use the comparator value than current count.*/ - cnt = hpet_readl(HPET_T1_CMP); + cnt = hpet_t1_cmp; cnt += hpet_tick*HZ/hpet_rtc_int_freq; hpet_writel(cnt, HPET_T1_CMP); + hpet_t1_cmp = cnt; } /* -- cgit v1.2.3-70-g09d2