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| author | Marcelo Tosatti <marcelo@kvack.org> | 2007-02-16 10:27:44 +0100 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-02-16 17:13:58 +0100 |
| commit | 07190a08eef3666a8687070226c8d403c1d548b7 (patch) | |
| tree | 20a9f7e9b6bf925a6721f88e438ec551fa8ce992 /arch/i386 | |
| parent | [PATCH] clocksource: Add verification (watchdog) helper (diff) | |
| download | linux-07190a08eef3666a8687070226c8d403c1d548b7.tar.xz linux-07190a08eef3666a8687070226c8d403c1d548b7.zip | |
[PATCH] Mark TSC on GeodeLX reliable
The Geode can safely use the TSC for highres, since:
1) Does not support frequency scaling,
2) The TSC _does_ count when the CPU is halted. Furthermore, the Geode
supports a mode called "suspension on halt", where Suspend mode (which
interacts with the power management states) is entered. TSC counting
during suspend mode is controlled by bit 8 of the Bus Controller
Configuration Register #0 (thanks Tom!).
3) no SMP :)
Check if "RTSC counts during suspension" and remove the requirement for
verification, so the clocksource code can safely select it as an timesource
for the highres timers subsystem.
Signed-off-by: Marcelo Tosatti <marcelo@kvack.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/i386')
| -rw-r--r-- | arch/i386/kernel/tsc.c | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/arch/i386/kernel/tsc.c b/arch/i386/kernel/tsc.c index 22931d24027c..3082a418635c 100644 --- a/arch/i386/kernel/tsc.c +++ b/arch/i386/kernel/tsc.c @@ -364,6 +364,25 @@ __cpuinit int unsynchronized_tsc(void) return tsc_unstable; } +/* + * Geode_LX - the OLPC CPU has a possibly a very reliable TSC + */ +#ifdef CONFIG_MGEODE_LX +/* RTSC counts during suspend */ +#define RTSC_SUSP 0x100 + +static void __init check_geode_tsc_reliable(void) +{ + unsigned long val; + + rdmsrl(MSR_GEODE_BUSCONT_CONF0, val); + if ((val & RTSC_SUSP)) + clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY; +} +#else +static inline void check_geode_tsc_reliable(void) { } +#endif + static int __init init_tsc_clocksource(void) { @@ -372,6 +391,7 @@ static int __init init_tsc_clocksource(void) dmi_check_system(bad_tsc_dmi_table); unsynchronized_tsc(); + check_geode_tsc_reliable(); current_tsc_khz = tsc_khz; clocksource_tsc.mult = clocksource_khz2mult(current_tsc_khz, clocksource_tsc.shift); |