[PATCH 0/3] x86 time bits

[PATCH 0/3] x86 time bits

[Peter Zijlstra]

Various x86 time keeping patches I've collected over the past week.

[PATCH 1/3] x86/tsc: Allow TSC calibration without PIT

[Peter Zijlstra]

[-- Attachment #1: peterz-no-pit.patch --]
[-- Type: text/plain, Size: 2250 bytes --]

Zhang Rui reported that a Surface Pro 4 will fail to boot with
lapic=notscdeadline. Part of the problem is that that machine doesn't
have a PIC.

If, for some reason, we fall back to TSC calibration, we rely on the
PIT to be present. Allow TSC calibration to reliably fall back to
HPET.

The below results in an accurate TSC measurement when forced on my
IVB:

  tsc: Unable to calibrate against PIT
  tsc: No reference (HPET/PMTIMER) available
  tsc: Unable to calibrate against PIT
  tsc: using HPET reference calibration
  tsc: Detected 2792.451 MHz processor

Cc: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 arch/x86/include/asm/i8259.h |    5 +++++
 arch/x86/kernel/tsc.c        |   18 ++++++++++++++++++
 2 files changed, 23 insertions(+)

--- a/arch/x86/include/asm/i8259.h
+++ b/arch/x86/include/asm/i8259.h
@@ -69,6 +69,11 @@ struct legacy_pic {
 extern struct legacy_pic *legacy_pic;
 extern struct legacy_pic null_legacy_pic;
 
+static inline bool has_legacy_pic(void)
+{
+	return legacy_pic != &null_legacy_pic;
+}
+
 static inline int nr_legacy_irqs(void)
 {
 	return legacy_pic->nr_legacy_irqs;
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -25,6 +25,7 @@
 #include <asm/geode.h>
 #include <asm/apic.h>
 #include <asm/intel-family.h>
+#include <asm/i8259.h>
 
 unsigned int __read_mostly cpu_khz;	/* TSC clocks / usec, not used here */
 EXPORT_SYMBOL(cpu_khz);
@@ -363,6 +364,20 @@ static unsigned long pit_calibrate_tsc(u
 	unsigned long tscmin, tscmax;
 	int pitcnt;
 
+	if (!has_legacy_pic()) {
+		/*
+		 * Relies on tsc_early_delay_calibrate() to have given us semi
+		 * usable udelay(), wait for the same 50ms we would have with
+		 * the PIT loop below.
+		 */
+		udelay(10 * USEC_PER_MSEC);
+		udelay(10 * USEC_PER_MSEC);
+		udelay(10 * USEC_PER_MSEC);
+		udelay(10 * USEC_PER_MSEC);
+		udelay(10 * USEC_PER_MSEC);
+		return ULONG_MAX;
+	}
+
 	/* Set the Gate high, disable speaker */
 	outb((inb(0x61) & ~0x02) | 0x01, 0x61);
 
@@ -487,6 +502,9 @@ static unsigned long quick_pit_calibrate
 	u64 tsc, delta;
 	unsigned long d1, d2;
 
+	if (!has_legacy_pic())
+		return 0;
+
 	/* Set the Gate high, disable speaker */
 	outb((inb(0x61) & ~0x02) | 0x01, 0x61);
 

[PATCH 2/3] x86/time: Unconditionally register legacy timer interrupt

[Peter Zijlstra]

[-- Attachment #1: peterz-uncondition-legacy-timer.patch --]
[-- Type: text/plain, Size: 786 bytes --]

Even without a PIC/PIT we need the legacy timer interrupt for HPET in
legacy replacement mode.

Cc: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 arch/x86/kernel/time.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/arch/x86/kernel/time.c
+++ b/arch/x86/kernel/time.c
@@ -69,9 +69,12 @@ static struct irqaction irq0  = {
 
 static void __init setup_default_timer_irq(void)
 {
-	if (!nr_legacy_irqs())
-		return;
-	setup_irq(0, &irq0);
+	/*
+	 * Unconditionally register the legacy timer; even without legacy
+	 * PIC/PIT we need this for the HPET0 in legacy replacement mode.
+	 */
+	if (setup_irq(0, &irq0))
+		pr_info("Failed to register legacy timer interrupt\n");
 }
 
 /* Default timer init function */

[PATCH 3/3] x86/tsc: Introduce early tsc clocksource

[Peter Zijlstra]

[-- Attachment #1: peterz-tsc-early.patch --]
[-- Type: text/plain, Size: 4051 bytes --]

Without TSC_KNOWN_FREQ we register the TSC clocksource so late we
first switch to the HPET. Using HPET on large CPU count machines is
undesirable.

Therefore register a tsc-early clocksource using the preliminary
tsc_khz from quick calibration. Then when the final TSC calibration
comes in, we can switch to that.

The only notably problem is that we must mark the real tsc clocksource
with CLOCK_SOURCE_VALID_FOR_HRES, otherwise we will not select it when
unregistering tsc-early. And we cannot leave tsc-early registered,
because then we'd fall back to it when we mark the tsc clocksource as
unstable.

Cc: Len Brown <lenb@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 arch/x86/kernel/tsc.c |   43 +++++++++++++++++++++++++++++++++----------
 1 file changed, 33 insertions(+), 10 deletions(-)

--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1005,8 +1005,6 @@ static void __init detect_art(void)
 
 /* clocksource code */
 
-static struct clocksource clocksource_tsc;
-
 static void tsc_resume(struct clocksource *cs)
 {
 	tsc_verify_tsc_adjust(true);
@@ -1057,12 +1055,31 @@ static void tsc_cs_tick_stable(struct cl
 /*
  * .mask MUST be CLOCKSOURCE_MASK(64). See comment above read_tsc()
  */
+static struct clocksource clocksource_tsc_early = {
+	.name                   = "tsc-early",
+	.rating                 = 299,
+	.read                   = read_tsc,
+	.mask                   = CLOCKSOURCE_MASK(64),
+	.flags                  = CLOCK_SOURCE_IS_CONTINUOUS |
+				  CLOCK_SOURCE_MUST_VERIFY,
+	.archdata               = { .vclock_mode = VCLOCK_TSC },
+	.resume			= tsc_resume,
+	.mark_unstable		= tsc_cs_mark_unstable,
+	.tick_stable		= tsc_cs_tick_stable,
+};
+
+/*
+ * Must mark VALID_FOR_HRES early such that when we unregister tsc_early
+ * this one will immediately take over. We will only register if TSC has
+ * been found good.
+ */
 static struct clocksource clocksource_tsc = {
 	.name                   = "tsc",
 	.rating                 = 300,
 	.read                   = read_tsc,
 	.mask                   = CLOCKSOURCE_MASK(64),
 	.flags                  = CLOCK_SOURCE_IS_CONTINUOUS |
+				  CLOCK_SOURCE_VALID_FOR_HRES |
 				  CLOCK_SOURCE_MUST_VERIFY,
 	.archdata               = { .vclock_mode = VCLOCK_TSC },
 	.resume			= tsc_resume,
@@ -1186,8 +1203,8 @@ static void tsc_refine_calibration_work(
 	int cpu;
 
 	/* Don't bother refining TSC on unstable systems */
-	if (check_tsc_unstable())
-		goto out;
+	if (tsc_unstable)
+		return;
 
 	/*
 	 * Since the work is started early in boot, we may be
@@ -1239,9 +1256,13 @@ static void tsc_refine_calibration_work(
 		set_cyc2ns_scale(tsc_khz, cpu, tsc_stop);
 
 out:
+	if (tsc_unstable)
+		return;
+
 	if (boot_cpu_has(X86_FEATURE_ART))
 		art_related_clocksource = &clocksource_tsc;
 	clocksource_register_khz(&clocksource_tsc, tsc_khz);
+	clocksource_unregister(&clocksource_tsc_early);
 }
 
 
@@ -1250,13 +1271,11 @@ static int __init init_tsc_clocksource(v
 	if (!boot_cpu_has(X86_FEATURE_TSC) || tsc_disabled > 0 || !tsc_khz)
 		return 0;
 
+	if (check_tsc_unstable())
+		return 0;
+
 	if (tsc_clocksource_reliable)
 		clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;
-	/* lower the rating if we already know its unstable: */
-	if (check_tsc_unstable()) {
-		clocksource_tsc.rating = 0;
-		clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS;
-	}
 
 	if (boot_cpu_has(X86_FEATURE_NONSTOP_TSC_S3))
 		clocksource_tsc.flags |= CLOCK_SOURCE_SUSPEND_NONSTOP;
@@ -1269,6 +1288,7 @@ static int __init init_tsc_clocksource(v
 		if (boot_cpu_has(X86_FEATURE_ART))
 			art_related_clocksource = &clocksource_tsc;
 		clocksource_register_khz(&clocksource_tsc, tsc_khz);
+		clocksource_unregister(&clocksource_tsc_early);
 		return 0;
 	}
 
@@ -1367,9 +1387,12 @@ void __init tsc_init(void)
 
 	check_system_tsc_reliable();
 
-	if (unsynchronized_tsc())
+	if (unsynchronized_tsc()) {
 		mark_tsc_unstable("TSCs unsynchronized");
+		return;
+	}
 
+	clocksource_register_khz(&clocksource_tsc_early, tsc_khz);
 	detect_art();
 }
 

[tip:x86/timers] x86/tsc: Allow TSC calibration without PIT

[tip-bot for Peter Zijlstra]

Commit-ID:  30c7e5b123673d5e570e238dbada2fb68a87212c
Gitweb:     https://git.kernel.org/tip/30c7e5b123673d5e570e238dbada2fb68a87212c
Author:     Peter Zijlstra <peterz@infradead.org>
AuthorDate: Fri, 22 Dec 2017 10:20:11 +0100
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sun, 14 Jan 2018 20:18:23 +0100

x86/tsc: Allow TSC calibration without PIT

Zhang Rui reported that a Surface Pro 4 will fail to boot with
lapic=notscdeadline. Part of the problem is that that machine doesn't have
a PIT.

If, for some reason, the TSC init has to fall back to TSC calibration, it
relies on the PIT to be present.

Allow TSC calibration to reliably fall back to HPET.

The below results in an accurate TSC measurement when forced on a IVB:

  tsc: Unable to calibrate against PIT
  tsc: No reference (HPET/PMTIMER) available
  tsc: Unable to calibrate against PIT
  tsc: using HPET reference calibration
  tsc: Detected 2792.451 MHz processor

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: len.brown@intel.com
Cc: rui.zhang@intel.com
Link: https://lkml.kernel.org/r/20171222092243.333145937@infradead.org

---
 arch/x86/include/asm/i8259.h |  5 +++++
 arch/x86/kernel/tsc.c        | 18 ++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/arch/x86/include/asm/i8259.h b/arch/x86/include/asm/i8259.h
index c8376b4..5cdcdbd 100644
--- a/arch/x86/include/asm/i8259.h
+++ b/arch/x86/include/asm/i8259.h
@@ -69,6 +69,11 @@ struct legacy_pic {
 extern struct legacy_pic *legacy_pic;
 extern struct legacy_pic null_legacy_pic;
 
+static inline bool has_legacy_pic(void)
+{
+	return legacy_pic != &null_legacy_pic;
+}
+
 static inline int nr_legacy_irqs(void)
 {
 	return legacy_pic->nr_legacy_irqs;
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index e169e85..a2c9dd8 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -25,6 +25,7 @@
 #include <asm/geode.h>
 #include <asm/apic.h>
 #include <asm/intel-family.h>
+#include <asm/i8259.h>
 
 unsigned int __read_mostly cpu_khz;	/* TSC clocks / usec, not used here */
 EXPORT_SYMBOL(cpu_khz);
@@ -363,6 +364,20 @@ static unsigned long pit_calibrate_tsc(u32 latch, unsigned long ms, int loopmin)
 	unsigned long tscmin, tscmax;
 	int pitcnt;
 
+	if (!has_legacy_pic()) {
+		/*
+		 * Relies on tsc_early_delay_calibrate() to have given us semi
+		 * usable udelay(), wait for the same 50ms we would have with
+		 * the PIT loop below.
+		 */
+		udelay(10 * USEC_PER_MSEC);
+		udelay(10 * USEC_PER_MSEC);
+		udelay(10 * USEC_PER_MSEC);
+		udelay(10 * USEC_PER_MSEC);
+		udelay(10 * USEC_PER_MSEC);
+		return ULONG_MAX;
+	}
+
 	/* Set the Gate high, disable speaker */
 	outb((inb(0x61) & ~0x02) | 0x01, 0x61);
 
@@ -487,6 +502,9 @@ static unsigned long quick_pit_calibrate(void)
 	u64 tsc, delta;
 	unsigned long d1, d2;
 
+	if (!has_legacy_pic())
+		return 0;
+
 	/* Set the Gate high, disable speaker */
 	outb((inb(0x61) & ~0x02) | 0x01, 0x61);
 

[tip:x86/timers] x86/time: Unconditionally register legacy timer interrupt

[tip-bot for Peter Zijlstra]

Commit-ID:  6d671e1b85c63e7a337ba76c1a154c091545cff8
Gitweb:     https://git.kernel.org/tip/6d671e1b85c63e7a337ba76c1a154c091545cff8
Author:     Peter Zijlstra <peterz@infradead.org>
AuthorDate: Fri, 22 Dec 2017 10:20:12 +0100
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sun, 14 Jan 2018 20:18:23 +0100

x86/time: Unconditionally register legacy timer interrupt

Even without a PIC/PIT the legacy timer interrupt is required for HPET in
legacy replacement mode.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: len.brown@intel.com
Cc: rui.zhang@intel.com
Link: https://lkml.kernel.org/r/20171222092243.382623763@infradead.org

---
 arch/x86/kernel/time.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/time.c b/arch/x86/kernel/time.c
index 749d189..774ebaf 100644
--- a/arch/x86/kernel/time.c
+++ b/arch/x86/kernel/time.c
@@ -69,9 +69,12 @@ static struct irqaction irq0  = {
 
 static void __init setup_default_timer_irq(void)
 {
-	if (!nr_legacy_irqs())
-		return;
-	setup_irq(0, &irq0);
+	/*
+	 * Unconditionally register the legacy timer; even without legacy
+	 * PIC/PIT we need this for the HPET0 in legacy replacement mode.
+	 */
+	if (setup_irq(0, &irq0))
+		pr_info("Failed to register legacy timer interrupt\n");
 }
 
 /* Default timer init function */

[tip:x86/timers] x86/tsc: Introduce early tsc clocksource

[tip-bot for Peter Zijlstra]

Commit-ID:  aa83c45762a242acce9b35020363225a7b59d7c9
Gitweb:     https://git.kernel.org/tip/aa83c45762a242acce9b35020363225a7b59d7c9
Author:     Peter Zijlstra <peterz@infradead.org>
AuthorDate: Fri, 22 Dec 2017 10:20:13 +0100
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sun, 14 Jan 2018 20:18:23 +0100

x86/tsc: Introduce early tsc clocksource

Without TSC_KNOWN_FREQ the TSC clocksource is registered so late that the
kernel first switches to the HPET. Using HPET on large CPU count machines is
undesirable.

Therefore register a tsc-early clocksource using the preliminary tsc_khz
from quick calibration. Then when the final TSC calibration is done, it
can switch to the tuned frequency.

The only notably problem is that the real tsc clocksource must be marked
with CLOCK_SOURCE_VALID_FOR_HRES, otherwise it will not be selected when
unregistering tsc-early. tsc-early cannot be left registered, because then
the clocksource code would fall back to it when we tsc clocksource is
marked unstable later.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: len.brown@intel.com
Cc: rui.zhang@intel.com
Cc: Len Brown <lenb@kernel.org>
Link: https://lkml.kernel.org/r/20171222092243.431585460@infradead.org

---
 arch/x86/kernel/tsc.c | 43 +++++++++++++++++++++++++++++++++----------
 1 file changed, 33 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index a2c9dd8..fb43027 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1006,8 +1006,6 @@ static void __init detect_art(void)
 
 /* clocksource code */
 
-static struct clocksource clocksource_tsc;
-
 static void tsc_resume(struct clocksource *cs)
 {
 	tsc_verify_tsc_adjust(true);
@@ -1058,12 +1056,31 @@ static void tsc_cs_tick_stable(struct clocksource *cs)
 /*
  * .mask MUST be CLOCKSOURCE_MASK(64). See comment above read_tsc()
  */
+static struct clocksource clocksource_tsc_early = {
+	.name                   = "tsc-early",
+	.rating                 = 299,
+	.read                   = read_tsc,
+	.mask                   = CLOCKSOURCE_MASK(64),
+	.flags                  = CLOCK_SOURCE_IS_CONTINUOUS |
+				  CLOCK_SOURCE_MUST_VERIFY,
+	.archdata               = { .vclock_mode = VCLOCK_TSC },
+	.resume			= tsc_resume,
+	.mark_unstable		= tsc_cs_mark_unstable,
+	.tick_stable		= tsc_cs_tick_stable,
+};
+
+/*
+ * Must mark VALID_FOR_HRES early such that when we unregister tsc_early
+ * this one will immediately take over. We will only register if TSC has
+ * been found good.
+ */
 static struct clocksource clocksource_tsc = {
 	.name                   = "tsc",
 	.rating                 = 300,
 	.read                   = read_tsc,
 	.mask                   = CLOCKSOURCE_MASK(64),
 	.flags                  = CLOCK_SOURCE_IS_CONTINUOUS |
+				  CLOCK_SOURCE_VALID_FOR_HRES |
 				  CLOCK_SOURCE_MUST_VERIFY,
 	.archdata               = { .vclock_mode = VCLOCK_TSC },
 	.resume			= tsc_resume,
@@ -1187,8 +1204,8 @@ static void tsc_refine_calibration_work(struct work_struct *work)
 	int cpu;
 
 	/* Don't bother refining TSC on unstable systems */
-	if (check_tsc_unstable())
-		goto out;
+	if (tsc_unstable)
+		return;
 
 	/*
 	 * Since the work is started early in boot, we may be
@@ -1240,9 +1257,13 @@ static void tsc_refine_calibration_work(struct work_struct *work)
 		set_cyc2ns_scale(tsc_khz, cpu, tsc_stop);
 
 out:
+	if (tsc_unstable)
+		return;
+
 	if (boot_cpu_has(X86_FEATURE_ART))
 		art_related_clocksource = &clocksource_tsc;
 	clocksource_register_khz(&clocksource_tsc, tsc_khz);
+	clocksource_unregister(&clocksource_tsc_early);
 }
 
 
@@ -1251,13 +1272,11 @@ static int __init init_tsc_clocksource(void)
 	if (!boot_cpu_has(X86_FEATURE_TSC) || tsc_disabled > 0 || !tsc_khz)
 		return 0;
 
+	if (check_tsc_unstable())
+		return 0;
+
 	if (tsc_clocksource_reliable)
 		clocksource_tsc.flags &= ~CLOCK_SOURCE_MUST_VERIFY;
-	/* lower the rating if we already know its unstable: */
-	if (check_tsc_unstable()) {
-		clocksource_tsc.rating = 0;
-		clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS;
-	}
 
 	if (boot_cpu_has(X86_FEATURE_NONSTOP_TSC_S3))
 		clocksource_tsc.flags |= CLOCK_SOURCE_SUSPEND_NONSTOP;
@@ -1270,6 +1289,7 @@ static int __init init_tsc_clocksource(void)
 		if (boot_cpu_has(X86_FEATURE_ART))
 			art_related_clocksource = &clocksource_tsc;
 		clocksource_register_khz(&clocksource_tsc, tsc_khz);
+		clocksource_unregister(&clocksource_tsc_early);
 		return 0;
 	}
 
@@ -1374,9 +1394,12 @@ void __init tsc_init(void)
 
 	check_system_tsc_reliable();
 
-	if (unsynchronized_tsc())
+	if (unsynchronized_tsc()) {
 		mark_tsc_unstable("TSCs unsynchronized");
+		return;
+	}
 
+	clocksource_register_khz(&clocksource_tsc_early, tsc_khz);
 	detect_art();
 }