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Message-Id: <1438988495-9942-3-git-send-email-christopher.s.hall@intel.com>
Date: Fri, 7 Aug 2015 16:01:33 -0700
From: Christopher Hall <christopher.s.hall@...el.com>
To: john.stultz@...aro.org, tglx@...utronix.de,
richardcochran@...il.com, mingo@...hat.com,
jeffrey.t.kirsher@...el.com, john.ronciak@...el.com, hpa@...or.com,
x86@...nel.org
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
Christopher Hall <christopher.s.hall@...el.com>
Subject: [PATCH v2 2/4] Add ART initialization code
add private struct correlated_ts member used by get_ts() code
added EXPORTs making get_correlated_timestamp() function and
art_timestamper accessible
Add special case for denominator of 2 (art_to_tsc())
---
arch/x86/include/asm/cpufeature.h | 3 ++-
arch/x86/include/asm/tsc.h | 1 +
arch/x86/kernel/tsc.c | 42 ++++++++++++++++++++++++++-------------
include/linux/clocksource.h | 8 +++++---
kernel/time/timekeeping.c | 1 +
5 files changed, 37 insertions(+), 18 deletions(-)
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 3d6606f..a9322e5 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -85,7 +85,7 @@
#define X86_FEATURE_P4 ( 3*32+ 7) /* "" P4 */
#define X86_FEATURE_CONSTANT_TSC ( 3*32+ 8) /* TSC ticks at a constant rate */
#define X86_FEATURE_UP ( 3*32+ 9) /* smp kernel running on up */
-/* free, was #define X86_FEATURE_FXSAVE_LEAK ( 3*32+10) * "" FXSAVE leaks FOP/FIP/FOP */
+#define X86_FEATURE_ART (3*32+10) /* Platform has always running timer (ART) */
#define X86_FEATURE_ARCH_PERFMON ( 3*32+11) /* Intel Architectural PerfMon */
#define X86_FEATURE_PEBS ( 3*32+12) /* Precise-Event Based Sampling */
#define X86_FEATURE_BTS ( 3*32+13) /* Branch Trace Store */
@@ -352,6 +352,7 @@ extern const char * const x86_bug_flags[NBUGINTS*32];
#define cpu_has_de boot_cpu_has(X86_FEATURE_DE)
#define cpu_has_pse boot_cpu_has(X86_FEATURE_PSE)
#define cpu_has_tsc boot_cpu_has(X86_FEATURE_TSC)
+#define cpu_has_art boot_cpu_has(X86_FEATURE_ART)
#define cpu_has_pge boot_cpu_has(X86_FEATURE_PGE)
#define cpu_has_apic boot_cpu_has(X86_FEATURE_APIC)
#define cpu_has_sep boot_cpu_has(X86_FEATURE_SEP)
diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h
index 94605c0..0089991 100644
--- a/arch/x86/include/asm/tsc.h
+++ b/arch/x86/include/asm/tsc.h
@@ -53,6 +53,7 @@ extern int check_tsc_disabled(void);
extern unsigned long native_calibrate_tsc(void);
extern int tsc_clocksource_reliable;
+extern struct correlated_cs art_timestamper;
/*
* Boot-time check whether the TSCs are synchronized across
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index a90aa6a..0a2f336 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1059,6 +1059,9 @@ int unsynchronized_tsc(void)
return 0;
}
+#define ART_CPUID_LEAF (0x15)
+#define ART_MIN_DENOMINATOR (2)
+
static u32 tsc_numerator;
static u32 tsc_denominator;
/*
@@ -1067,19 +1070,29 @@ static u32 tsc_denominator;
*/
static u64 tsc_adjust;
-static u64 art_to_tsc(u64 cycles)
+static u64 art_to_tsc(struct correlated_cs *cs, u64 cycles)
{
u64 tmp, res = tsc_adjust;
- res += (cycles / tsc_denominator) * tsc_numerator;
- tmp = (cycles % tsc_denominator) * tsc_numerator;
- res += tmp / tsc_denominator;
+ switch (tsc_denominator) {
+ default:
+ res += (cycles / tsc_denominator) * tsc_numerator;
+ tmp = (cycles % tsc_denominator) * tsc_numerator;
+ res += tmp / tsc_denominator;
+ break;
+ case 2:
+ res += (cycles >> 1) * tsc_numerator;
+ tmp = (cycles & 0x1) * tsc_numerator;
+ res += tmp >> 1;
+ break;
+ }
return res;
}
struct correlated_cs art_timestamper = {
.convert = art_to_tsc,
};
+EXPORT_SYMBOL(art_timestamper);
static void tsc_refine_calibration_work(struct work_struct *work);
static DECLARE_DELAYED_WORK(tsc_irqwork, tsc_refine_calibration_work);
@@ -1103,6 +1116,7 @@ static void tsc_refine_calibration_work(struct work_struct *work)
static int hpet;
u64 tsc_stop, ref_stop, delta;
unsigned long freq;
+ unsigned int unused[2];
/* Don't bother refining TSC on unstable systems */
if (check_tsc_unstable())
@@ -1150,17 +1164,17 @@ static void tsc_refine_calibration_work(struct work_struct *work)
(unsigned long)tsc_khz / 1000,
(unsigned long)tsc_khz % 1000);
- /*
- * TODO:
- *
- * If the system has ART, initialize the art_to_tsc conversion
- * and set: art_timestamp.related_cs = &tsc_clocksource.
- *
- * Before that point a call to get_correlated_timestamp will
- * fail the clocksource match check.
- */
-
out:
+ if (boot_cpu_data.cpuid_level >= ART_CPUID_LEAF) {
+ cpuid(ART_CPUID_LEAF, &tsc_denominator, &tsc_numerator, unused,
+ unused+1);
+
+ if (tsc_denominator >= ART_MIN_DENOMINATOR) {
+ set_cpu_cap(&boot_cpu_data, X86_FEATURE_ART);
+ art_timestamper.related_cs = &clocksource_tsc;
+ }
+ }
+
clocksource_register_khz(&clocksource_tsc, tsc_khz);
}
diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 2ed3d0c..46ce54b 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -267,7 +267,8 @@ static inline void acpi_generic_timer_init(void) { }
*/
struct correlated_cs {
struct clocksource *related_cs;
- u64 (*convert)(u64 cycles);
+ u64 (*convert)(struct correlated_cs *cs,
+ u64 cycles);
};
struct correlated_ts;
@@ -285,7 +286,8 @@ struct correlated_ts {
int (*get_ts)(struct correlated_ts *ts);
u64 system_ts;
u64 device_ts;
- u64 system_real;
- u64 system_raw;
+ ktime_t system_real;
+ ktime_t system_raw;
+ void *private;
};
#endif /* _LINUX_CLOCKSOURCE_H */
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 769a04b..abf8aec 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -946,6 +946,7 @@ int get_correlated_timestamp(struct correlated_ts *crt,
} while (read_seqcount_retry(&tk_core.seq, seq));
return 0;
}
+EXPORT_SYMBOL(get_correlated_timestamp);
/**
* do_gettimeofday - Returns the time of day in a timeval
--
1.9.1
--
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