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authorRichard Henderson <rth@twiddle.net>2013-07-14 20:55:08 +0400
committerMatt Turner <mattst88@gmail.com>2013-11-17 04:33:18 +0400
commitdb2d3260617ae8c9076ef12e6de06bd5b3d82cd3 (patch)
tree700ee620482cdee9aef58c3d4c8bde7336394c5d /arch/alpha
parent85d0b3a573d8b711ee0c96199ac24a0f3283ed68 (diff)
downloadlinux-db2d3260617ae8c9076ef12e6de06bd5b3d82cd3.tar.xz
alpha: Enable the rpcc clocksource for single processor
Don't depend on SMP, just check the number of processors online. This allows a single distribution kernel to use the clocksource when run on a single processor machine. Do depend on whether or not we're using WTINT. Signed-off-by: Richard Henderson <rth@twiddle.net>
Diffstat (limited to 'arch/alpha')
-rw-r--r--arch/alpha/kernel/time.c67
1 files changed, 37 insertions, 30 deletions
diff --git a/arch/alpha/kernel/time.c b/arch/alpha/kernel/time.c
index 4c6c0fe47a7b..0d72e2df4b0e 100644
--- a/arch/alpha/kernel/time.c
+++ b/arch/alpha/kernel/time.c
@@ -184,6 +184,37 @@ common_init_rtc(void)
init_rtc_irq();
}
+
+#ifndef CONFIG_ALPHA_WTINT
+/*
+ * The RPCC as a clocksource primitive.
+ *
+ * While we have free-running timecounters running on all CPUs, and we make
+ * a half-hearted attempt in init_rtc_rpcc_info to sync the timecounter
+ * with the wall clock, that initialization isn't kept up-to-date across
+ * different time counters in SMP mode. Therefore we can only use this
+ * method when there's only one CPU enabled.
+ *
+ * When using the WTINT PALcall, the RPCC may shift to a lower frequency,
+ * or stop altogether, while waiting for the interrupt. Therefore we cannot
+ * use this method when WTINT is in use.
+ */
+
+static cycle_t read_rpcc(struct clocksource *cs)
+{
+ return rpcc();
+}
+
+static struct clocksource clocksource_rpcc = {
+ .name = "rpcc",
+ .rating = 300,
+ .read = read_rpcc,
+ .mask = CLOCKSOURCE_MASK(32),
+ .flags = CLOCK_SOURCE_IS_CONTINUOUS
+};
+#endif /* ALPHA_WTINT */
+
+
/* Validate a computed cycle counter result against the known bounds for
the given processor core. There's too much brokenness in the way of
timing hardware for any one method to work everywhere. :-(
@@ -294,33 +325,6 @@ rpcc_after_update_in_progress(void)
return rpcc();
}
-#ifndef CONFIG_SMP
-/* Until and unless we figure out how to get cpu cycle counters
- in sync and keep them there, we can't use the rpcc. */
-static cycle_t read_rpcc(struct clocksource *cs)
-{
- cycle_t ret = (cycle_t)rpcc();
- return ret;
-}
-
-static struct clocksource clocksource_rpcc = {
- .name = "rpcc",
- .rating = 300,
- .read = read_rpcc,
- .mask = CLOCKSOURCE_MASK(32),
- .flags = CLOCK_SOURCE_IS_CONTINUOUS
-};
-
-static inline void register_rpcc_clocksource(long cycle_freq)
-{
- clocksource_register_hz(&clocksource_rpcc, cycle_freq);
-}
-#else /* !CONFIG_SMP */
-static inline void register_rpcc_clocksource(long cycle_freq)
-{
-}
-#endif /* !CONFIG_SMP */
-
void __init
time_init(void)
{
@@ -362,20 +366,23 @@ time_init(void)
"and unable to estimate a proper value!\n");
}
+ /* See above for restrictions on using clocksource_rpcc. */
+#ifndef CONFIG_ALPHA_WTINT
+ if (hwrpb->nr_processors == 1)
+ clocksource_register_hz(&clocksource_rpcc, cycle_freq);
+#endif
+
/* From John Bowman <bowman@math.ualberta.ca>: allow the values
to settle, as the Update-In-Progress bit going low isn't good
enough on some hardware. 2ms is our guess; we haven't found
bogomips yet, but this is close on a 500Mhz box. */
__delay(1000000);
-
if (HZ > (1<<16)) {
extern void __you_loose (void);
__you_loose();
}
- register_rpcc_clocksource(cycle_freq);
-
state.last_time = cc1;
state.scaled_ticks_per_cycle
= ((unsigned long) HZ << FIX_SHIFT) / cycle_freq;