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authorMarcelo Tosatti <marcelo@kvack.org>2007-02-16 01:27:44 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-02-16 08:13:58 -0800
commit07190a08eef3666a8687070226c8d403c1d548b7 (patch)
tree20a9f7e9b6bf925a6721f88e438ec551fa8ce992 /arch/i386/kernel
parent5d8b34fdcb384161552d01ee8f34af5ff11f9684 (diff)
[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/kernel')
-rw-r--r--arch/i386/kernel/tsc.c20
1 files changed, 20 insertions, 0 deletions
diff --git a/arch/i386/kernel/tsc.c b/arch/i386/kernel/tsc.c
index 22931d24027..3082a418635 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);