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Message-Id: <20060809021739.23103.98698.sendpatchset@cog.beaverton.ibm.com>
Date: Tue, 8 Aug 2006 22:17:40 -0400
From: john stultz <johnstul@...ibm.com>
To: ak@...e.de
Cc: john stultz <johnstul@...ibm.com>, linux-kernel@...r.kernel.org
Subject: [RFC][PATCH 5/6] x86_64: Clocksources for x86-64
Re-add TSC and HPET support to x86_64 via clocksource infrastructure.
Signed-off-by: John Stultz <johnstul@...ibm.com>
arch/x86_64/kernel/time.c | 133 +++++++++++++++++++++++++++++++++++++++++++--
include/asm-x86_64/timex.h | 3 +
2 files changed, 133 insertions(+), 3 deletions(-)
linux-2.6.18-rc4_timeofday-arch-x86-64-part4_C5.patch
============================================
diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
index d18230a..546abc7 100644
--- a/arch/x86_64/kernel/time.c
+++ b/arch/x86_64/kernel/time.c
@@ -39,6 +39,7 @@
#include <asm/sections.h>
#include <linux/cpufreq.h>
#include <linux/hpet.h>
+#include <linux/clocksource.h>
#ifdef CONFIG_X86_LOCAL_APIC
#include <asm/apic.h>
#endif
@@ -60,8 +61,9 @@ static int notsc __initdata = 0;
#define NS_SCALE 10 /* 2^10, carefully chosen */
#define US_SCALE 32 /* 2^32, arbitralrily chosen */
-unsigned int cpu_khz; /* TSC clocks / usec, not used here */
+unsigned int cpu_khz; /* CPU clocks / usec, not used here */
EXPORT_SYMBOL(cpu_khz);
+unsigned int tsc_khz; /* TSC clocks / usec, not used here */
unsigned long hpet_address;
static unsigned long hpet_period; /* fsecs / HPET clock */
unsigned long hpet_tick; /* HPET clocks / interrupt */
@@ -382,8 +384,9 @@ static int time_cpufreq_notifier(struct
cpufreq_scale(loops_per_jiffy_ref, ref_freq, freq->new);
cpu_khz = cpufreq_scale(cpu_khz_ref, ref_freq, freq->new);
- if (!(freq->flags & CPUFREQ_CONST_LOOPS))
- vxtime.tsc_quot = (USEC_PER_MSEC << US_SCALE) / cpu_khz;
+ if (!(freq->flags & CPUFREQ_CONST_LOOPS)) {
+ tsc_khz = cpu_khz;
+ }
}
set_cyc2ns_scale(cpu_khz_ref);
@@ -659,6 +662,10 @@ void __init time_init(void)
cpu_khz = pit_calibrate_tsc();
timename = "PIT";
}
+ tsc_khz = cpu_khz;
+
+ if (unsynchronized_tsc())
+ mark_tsc_unstable();
printk(KERN_INFO "time.c: Detected %d.%03d MHz processor.\n",
cpu_khz / 1000, cpu_khz % 1000);
@@ -999,3 +1006,123 @@ int __init notsc_setup(char *s)
}
__setup("notsc", notsc_setup);
+
+
+/* clock source code: */
+
+static unsigned long current_tsc_khz = 0;
+
+static int tsc_update_callback(void);
+
+static cycle_t read_tsc(void)
+{
+ cycle_t ret;
+ rdtscll(ret);
+ return ret;
+}
+
+static struct clocksource clocksource_tsc = {
+ .name = "tsc",
+ .rating = 300,
+ .read = read_tsc,
+ .mask = (cycle_t)-1,
+ .mult = 0, /* to be set */
+ .shift = 22,
+ .update_callback = tsc_update_callback,
+ .is_continuous = 1,
+};
+
+static int tsc_update_callback(void)
+{
+ int change = 0;
+
+ /* check to see if we should switch to the safe clocksource: */
+ if (clocksource_tsc.rating != 50 && check_tsc_unstable()) {
+ clocksource_tsc.rating = 50;
+ clocksource_reselect();
+ change = 1;
+ }
+
+ /* only update if tsc_khz has changed: */
+ if (current_tsc_khz != tsc_khz){
+ current_tsc_khz = tsc_khz;
+ clocksource_tsc.mult = clocksource_khz2mult(current_tsc_khz,
+ clocksource_tsc.shift);
+ change = 1;
+ }
+ return change;
+}
+
+static int __init init_tsc_clocksource(void)
+{
+ if (!notsc && tsc_khz) {
+ current_tsc_khz = tsc_khz;
+ clocksource_tsc.mult = clocksource_khz2mult(current_tsc_khz,
+ clocksource_tsc.shift);
+ return clocksource_register(&clocksource_tsc);
+ }
+ return 0;
+}
+
+module_init(init_tsc_clocksource);
+
+
+#define HPET_MASK 0xFFFFFFFF
+#define HPET_SHIFT 22
+
+/* FSEC = 10^-15 NSEC = 10^-9 */
+#define FSEC_PER_NSEC 1000000
+
+static void *hpet_ptr;
+
+static cycle_t read_hpet(void)
+{
+ return (cycle_t)readl(hpet_ptr);
+}
+
+struct clocksource clocksource_hpet = {
+ .name = "hpet",
+ .rating = 250,
+ .read = read_hpet,
+ .mask = (cycle_t)HPET_MASK,
+ .mult = 0, /* set below */
+ .shift = HPET_SHIFT,
+ .is_continuous = 1,
+};
+
+static int __init init_hpet_clocksource(void)
+{
+ unsigned long hpet_period;
+ void __iomem *hpet_base;
+ u64 tmp;
+
+ if (!hpet_address)
+ return -ENODEV;
+
+ /* calculate the hpet address: */
+ hpet_base =
+ (void __iomem*)ioremap_nocache(hpet_address, HPET_MMAP_SIZE);
+ hpet_ptr = hpet_base + HPET_COUNTER;
+
+ /* calculate the frequency: */
+ hpet_period = readl(hpet_base + HPET_PERIOD);
+
+ /*
+ * hpet period is in femto seconds per cycle
+ * so we need to convert this to ns/cyc units
+ * aproximated by mult/2^shift
+ *
+ * fsec/cyc * 1nsec/1000000fsec = nsec/cyc = mult/2^shift
+ * fsec/cyc * 1ns/1000000fsec * 2^shift = mult
+ * fsec/cyc * 2^shift * 1nsec/1000000fsec = mult
+ * (fsec/cyc << shift)/1000000 = mult
+ * (hpet_period << shift)/FSEC_PER_NSEC = mult
+ */
+ tmp = (u64)hpet_period << HPET_SHIFT;
+ do_div(tmp, FSEC_PER_NSEC);
+ clocksource_hpet.mult = (u32)tmp;
+
+ return clocksource_register(&clocksource_hpet);
+}
+
+module_init(init_hpet_clocksource);
diff --git a/include/asm-x86_64/timex.h b/include/asm-x86_64/timex.h
index b9e5320..11c6820 100644
--- a/include/asm-x86_64/timex.h
+++ b/include/asm-x86_64/timex.h
@@ -40,6 +40,9 @@ static __always_inline cycles_t get_cycl
}
extern unsigned int cpu_khz;
+extern unsigned int tsc_khz;
+
+extern void mark_tsc_unstable(void);
extern int read_current_timer(unsigned long *timer_value);
#define ARCH_HAS_READ_CURRENT_TIMER 1
-
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