From 312df5f1a1da780e084b328bcabb02a6dcd044c3 Mon Sep 17 00:00:00 2001 From: Andi Kleen Date: Mon, 16 May 2005 21:53:28 -0700 Subject: [PATCH] x86_64: Add pmtimer support There are unfortunately more and more multi processor Opteron systems which don't have HPET timer support in the southbridge. This covers in particular Nvidia and VIA chipsets. They also don't guarantee that the TSCs are synchronized between CPUs; and especially with MP powernow the systems are nearly unusable because the time gets very inconsistent between CPUs. The timer code for x86-64 was originally written under the assumption that we could fall back to the HPET timer on such systems. But this doesn't work there. Another alternative is to use the ACPI PM timer as primary time source. This patch does that. The kernel only uses PM timer when there is no other choice because it has some disadvantages. Ported over from i386. It should be faster than the i386 version because I dropped the "read three times" workaround, but is still considerable slower than HPET and also does not work together with vsyscalls which have to be disabled. Cc: Signed-off-by: Andi Kleen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/x86_64/Kconfig | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'arch/x86_64/Kconfig') diff --git a/arch/x86_64/Kconfig b/arch/x86_64/Kconfig index 44ee7f6..82cb2a3 100644 --- a/arch/x86_64/Kconfig +++ b/arch/x86_64/Kconfig @@ -303,6 +303,20 @@ config HPET_TIMER as it is off-chip. You can find the HPET spec at . +config X86_PM_TIMER + bool "PM timer" + default y + help + Support the ACPI PM timer for time keeping. This is slow, + but is useful on some chipsets without HPET on systems with more + than one CPU. On a single processor or single socket multi core + system it is normally not required. + When the PM timer is active 64bit vsyscalls are disabled + and should not be enabled (/proc/sys/kernel/vsyscall64 should + not be changed). + The kernel selects the PM timer only as a last resort, so it is + useful to enable just in case. + config HPET_EMULATE_RTC bool "Provide RTC interrupt" depends on HPET_TIMER && RTC=y -- cgit v1.1