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* [PATCH 1/2] powerpc/timer - large decrementer support
@ 2016-04-12  4:38 Oliver O'Halloran
  2016-04-12  4:38 ` [PATCH 2/2] KVM: PPC: hypervisor " Oliver O'Halloran
  2016-04-12  7:19 ` [PATCH 1/2] powerpc/timer - " Balbir Singh
  0 siblings, 2 replies; 8+ messages in thread
From: Oliver O'Halloran @ 2016-04-12  4:38 UTC (permalink / raw)
  To: linuxppc-dev; +Cc: Oliver O'Halloran, Jack Miller

POWER ISA v3 adds large decrementer (LD) mode of operation which increases
the size of the decrementer register from 32 bits to an implementation
defined with of up to 64 bits.

This patch adds support for the LD on processors with the CPU_FTR_ARCH_300
cpu feature flag set. Even for CPUs with this feature LD mode is only
enabled when the property ibm,dec-bits devicetree property is supplied
for the boot CPU. The decrementer value is a signed quantity (with
negative values indicating a pending exception) and this property is
required to find the maximum positive decrementer value. If this property
is not supplied then the traditional decrementer width of 32 bits is
assumed and LD mode is disabled.

This patch was based on inital work by Jack Miller.

Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Cc: Jack Miller <jack@codezen.org>
---
 arch/powerpc/include/asm/reg.h  |  1 +
 arch/powerpc/include/asm/time.h |  6 +--
 arch/powerpc/kernel/time.c      | 89 +++++++++++++++++++++++++++++++++++++----
 3 files changed, 86 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index f5f4c66bbbc9..ff581ed1ab9d 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -332,6 +332,7 @@
 #define   LPCR_AIL_0	0x00000000	/* MMU off exception offset 0x0 */
 #define   LPCR_AIL_3	0x01800000	/* MMU on exception offset 0xc00...4xxx */
 #define   LPCR_ONL	0x00040000	/* online - PURR/SPURR count */
+#define   LPCR_LD	0x00020000	/* large decremeter */
 #define   LPCR_PECE	0x0001f000	/* powersave exit cause enable */
 #define     LPCR_PECEDP	0x00010000	/* directed priv dbells cause exit */
 #define     LPCR_PECEDH	0x00008000	/* directed hyp dbells cause exit */
diff --git a/arch/powerpc/include/asm/time.h b/arch/powerpc/include/asm/time.h
index 1092fdd7e737..09211640a0e0 100644
--- a/arch/powerpc/include/asm/time.h
+++ b/arch/powerpc/include/asm/time.h
@@ -146,7 +146,7 @@ static inline void set_tb(unsigned int upper, unsigned int lower)
  * in auto-reload mode.  The problem is PIT stops counting when it
  * hits zero.  If it would wrap, we could use it just like a decrementer.
  */
-static inline unsigned int get_dec(void)
+static inline u64 get_dec(void)
 {
 #if defined(CONFIG_40x)
 	return (mfspr(SPRN_PIT));
@@ -160,10 +160,10 @@ static inline unsigned int get_dec(void)
  * in when the decrementer generates its interrupt: on the 1 to 0
  * transition for Book E/4xx, but on the 0 to -1 transition for others.
  */
-static inline void set_dec(int val)
+static inline void set_dec(u64 val)
 {
 #if defined(CONFIG_40x)
-	mtspr(SPRN_PIT, val);
+	mtspr(SPRN_PIT, (u32) val);
 #else
 #ifndef CONFIG_BOOKE
 	--val;
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index 81b0900a39ee..0afaef6b5b6a 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -95,7 +95,8 @@ static struct clocksource clocksource_timebase = {
 	.read         = timebase_read,
 };
 
-#define DECREMENTER_MAX	0x7fffffff
+#define DECREMENTER_DEFAULT_MAX 0x7FFFFFFF
+u64 decrementer_max = DECREMENTER_DEFAULT_MAX;
 
 static int decrementer_set_next_event(unsigned long evt,
 				      struct clock_event_device *dev);
@@ -503,7 +504,7 @@ static void __timer_interrupt(void)
 		__this_cpu_inc(irq_stat.timer_irqs_event);
 	} else {
 		now = *next_tb - now;
-		if (now <= DECREMENTER_MAX)
+		if (now <= decrementer_max)
 			set_dec((int)now);
 		/* We may have raced with new irq work */
 		if (test_irq_work_pending())
@@ -534,7 +535,7 @@ void timer_interrupt(struct pt_regs * regs)
 	/* Ensure a positive value is written to the decrementer, or else
 	 * some CPUs will continue to take decrementer exceptions.
 	 */
-	set_dec(DECREMENTER_MAX);
+	set_dec(decrementer_max);
 
 	/* Some implementations of hotplug will get timer interrupts while
 	 * offline, just ignore these and we also need to set
@@ -562,6 +563,7 @@ void timer_interrupt(struct pt_regs * regs)
 	irq_enter();
 
 	__timer_interrupt();
+
 	irq_exit();
 	set_irq_regs(old_regs);
 }
@@ -582,9 +584,9 @@ static void generic_suspend_disable_irqs(void)
 	 * with suspending.
 	 */
 
-	set_dec(DECREMENTER_MAX);
+	set_dec(decrementer_max);
 	local_irq_disable();
-	set_dec(DECREMENTER_MAX);
+	set_dec(decrementer_max);
 }
 
 static void generic_suspend_enable_irqs(void)
@@ -865,7 +867,7 @@ static int decrementer_set_next_event(unsigned long evt,
 
 static int decrementer_shutdown(struct clock_event_device *dev)
 {
-	decrementer_set_next_event(DECREMENTER_MAX, dev);
+	decrementer_set_next_event(decrementer_max, dev);
 	return 0;
 }
 
@@ -891,6 +893,72 @@ static void register_decrementer_clockevent(int cpu)
 	clockevents_register_device(dec);
 }
 
+static inline bool large_dec_on(void)
+{
+	return (mfspr(SPRN_LPCR) & LPCR_LD) == LPCR_LD;
+}
+
+static bool large_decrementer_supported(void)
+{
+	return cpu_has_feature(CPU_FTR_ARCH_300);
+}
+
+/* enables the large decrementer for the current CPU */
+static void enable_large_decrementer(void)
+{
+	/* do we have a large decrementer? */
+	if (!large_decrementer_supported())
+		return;
+
+	/* do we need a large decrementer? */
+	if (decrementer_max <= DECREMENTER_DEFAULT_MAX)
+		return;
+
+	mtspr(SPRN_LPCR, mfspr(SPRN_LPCR) | LPCR_LD);
+
+	if (!large_dec_on()) {
+		decrementer_max = DECREMENTER_DEFAULT_MAX;
+
+		pr_debug("Failed to enable large dec on CPU %d, "
+			"limiting to 32 bits", smp_processor_id());
+	}
+}
+
+static void __init set_decrementer_max(void)
+{
+	struct device_node *cpu;
+	const __be32 *fp;
+	u64 bits = 32;
+
+	/* dt node exists? */
+	cpu = of_find_node_by_type(NULL, "cpu");
+	if(cpu)
+		fp = of_get_property(cpu, "ibm,dec-bits", NULL);
+
+	if(cpu && fp) {
+		bits = of_read_number(fp, 1);
+
+		/* clamp to sane values */
+		if (bits > 64)
+			bits = 64;
+		if (bits < 32)
+			bits = 32;
+
+		/* Firmware says we support large dec but this cpu doesn't we
+		 * should warn about it. We can still limp along with default
+		 * 32 bit dec, but something is broken. */
+		if (!large_decrementer_supported()) {
+			WARN_ON(bits > 32);
+			bits = 32;
+		}
+
+		decrementer_max = (1ul << (bits - 1)) - 1;
+	}
+
+	pr_info("time_init: %llu bit decrementer (max: %llx)\n",
+		bits, decrementer_max);
+}
+
 static void __init init_decrementer_clockevent(void)
 {
 	int cpu = smp_processor_id();
@@ -898,7 +966,7 @@ static void __init init_decrementer_clockevent(void)
 	clockevents_calc_mult_shift(&decrementer_clockevent, ppc_tb_freq, 4);
 
 	decrementer_clockevent.max_delta_ns =
-		clockevent_delta2ns(DECREMENTER_MAX, &decrementer_clockevent);
+		clockevent_delta2ns(decrementer_max, &decrementer_clockevent);
 	decrementer_clockevent.min_delta_ns =
 		clockevent_delta2ns(2, &decrementer_clockevent);
 
@@ -907,6 +975,9 @@ static void __init init_decrementer_clockevent(void)
 
 void secondary_cpu_time_init(void)
 {
+	/* Enable the large decrementer (if we need to) */
+	enable_large_decrementer();
+
 	/* Start the decrementer on CPUs that have manual control
 	 * such as BookE
 	 */
@@ -972,6 +1043,10 @@ void __init time_init(void)
 	vdso_data->tb_update_count = 0;
 	vdso_data->tb_ticks_per_sec = tb_ticks_per_sec;
 
+	/* initialise and enable the large decrementer (if we have one) */
+	set_decrementer_max();
+	enable_large_decrementer();
+
 	/* Start the decrementer on CPUs that have manual control
 	 * such as BookE
 	 */
-- 
2.5.5

^ permalink raw reply related	[flat|nested] 8+ messages in thread
* Re: [PATCH v3 1/2] powerpc/timer - large decrementer support
@ 2016-05-31  6:25 Michael Neuling
  2016-05-31  7:16 ` [PATCH " Oliver O'Halloran
  0 siblings, 1 reply; 8+ messages in thread
From: Michael Neuling @ 2016-05-31  6:25 UTC (permalink / raw)
  To: Oliver O'Halloran, linuxppc-dev; +Cc: Jack Miller, Michael Ellerman

On Tue, 2016-05-10 at 14:57 +1000, Oliver O'Halloran wrote:
> POWER ISA v3 adds large decrementer (LD) mode of operation which increase=
s
> the size of the decrementer register from 32 bits to an implementation
> defined with of up to 64 bits.
>=20
> This patch adds support for the LD on processors with the CPU_FTR_ARCH_30=
0
> cpu feature flag set. For CPUs with this feature LD mode is enabled when
> when the ibm,dec-bits devicetree property is supplied for the boot CPU. T=
he
> decrementer value is a signed quantity (with negative values indicating a
> pending exception) and this property is required to find the maximum
> positive decrementer value. If this property is not supplied then the
> traditional decrementer width of 32 bits is assumed and LD mode is disabl=
ed.
>=20
> This patch was based on initial work by Jack Miller.
>=20
> Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
> Cc: Michael Neuling <mikey@neuling.org>
> Cc: Balbir Singh <bsingharora@gmail.com>
> Cc: Jack Miller <jack@codezen.org>

A couple or minor comments below. =C2=A0

I've tested this against v4.7-rc1 in the systemsim p9 model (not public
yet), with NO_HZ_FULL. From xmon I can see larger dec values being used=C2=
=A0
("Sr 16" in xmon).

If you fix the comments below I'm happy to ACK it.

Acked-by: Michael Neuling <mikey@neuling.org>


> ---
> =C2=A0arch/powerpc/include/asm/reg.h=C2=A0=C2=A0|=C2=A0=C2=A01 +
> =C2=A0arch/powerpc/include/asm/time.h |=C2=A0=C2=A06 +--
> =C2=A0arch/powerpc/kernel/time.c=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0| 92 =
+++++++++++++++++++++++++++++++++++++----
> =C2=A03 files changed, 89 insertions(+), 10 deletions(-)
>=20
> diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/re=
g.h
> index f5f4c66bbbc9..ff581ed1ab9d 100644
> --- a/arch/powerpc/include/asm/reg.h
> +++ b/arch/powerpc/include/asm/reg.h
> @@ -332,6 +332,7 @@
> =C2=A0#define=C2=A0=C2=A0=C2=A0LPCR_AIL_0	0x00000000	/* MMU off exception=
 offset 0x0 */
> =C2=A0#define=C2=A0=C2=A0=C2=A0LPCR_AIL_3	0x01800000	/* MMU on exception =
offset 0xc00...4xxx */
> =C2=A0#define=C2=A0=C2=A0=C2=A0LPCR_ONL	0x00040000	/* online - PURR/SPURR=
 count */
> +#define=C2=A0=C2=A0=C2=A0LPCR_LD	0x00020000	/* large decremeter */
> =C2=A0#define=C2=A0=C2=A0=C2=A0LPCR_PECE	0x0001f000	/* powersave exit cau=
se enable */
> =C2=A0#define=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0LPCR_PECEDP	0x00010000	/* dire=
cted priv dbells cause exit */
> =C2=A0#define=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0LPCR_PECEDH	0x00008000	/* dire=
cted hyp dbells cause exit */
> diff --git a/arch/powerpc/include/asm/time.h b/arch/powerpc/include/asm/t=
ime.h
> index 1092fdd7e737..09211640a0e0 100644
> --- a/arch/powerpc/include/asm/time.h
> +++ b/arch/powerpc/include/asm/time.h
> @@ -146,7 +146,7 @@ static inline void set_tb(unsigned int upper, unsigne=
d int lower)
> =C2=A0 * in auto-reload mode.=C2=A0=C2=A0The problem is PIT stops countin=
g when it
> =C2=A0 * hits zero.=C2=A0=C2=A0If it would wrap, we could use it just lik=
e a decrementer.
> =C2=A0 */
> -static inline unsigned int get_dec(void)
> +static inline u64 get_dec(void)
> =C2=A0{
> =C2=A0#if defined(CONFIG_40x)
> =C2=A0	return (mfspr(SPRN_PIT));
> @@ -160,10 +160,10 @@ static inline unsigned int get_dec(void)
> =C2=A0 * in when the decrementer generates its interrupt: on the 1 to 0
> =C2=A0 * transition for Book E/4xx, but on the 0 to -1 transition for oth=
ers.
> =C2=A0 */
> -static inline void set_dec(int val)
> +static inline void set_dec(u64 val)
> =C2=A0{
> =C2=A0#if defined(CONFIG_40x)
> -	mtspr(SPRN_PIT, val);
> +	mtspr(SPRN_PIT, (u32) val);
> =C2=A0#else
> =C2=A0#ifndef CONFIG_BOOKE
> =C2=A0	--val;
> diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
> index 81b0900a39ee..0656e80cadbf 100644
> --- a/arch/powerpc/kernel/time.c
> +++ b/arch/powerpc/kernel/time.c
> @@ -95,7 +95,8 @@ static struct clocksource clocksource_timebase =3D {
> =C2=A0	.read=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=3D tim=
ebase_read,
> =C2=A0};
> =C2=A0
> -#define DECREMENTER_MAX	0x7fffffff
> +#define DECREMENTER_DEFAULT_MAX 0x7FFFFFFF
> +u64 decrementer_max =3D DECREMENTER_DEFAULT_MAX;
> =C2=A0
> =C2=A0static int decrementer_set_next_event(unsigned long evt,
> =C2=A0				=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0struct clock_event_device *=
dev);
> @@ -503,7 +504,7 @@ static void __timer_interrupt(void)
> =C2=A0		__this_cpu_inc(irq_stat.timer_irqs_event);
> =C2=A0	} else {
> =C2=A0		now =3D *next_tb - now;
> -		if (now <=3D DECREMENTER_MAX)
> +		if (now <=3D decrementer_max)
> =C2=A0			set_dec((int)now);

You can remove the int cast here now since set_dec() takes a u64.

> =C2=A0		/* We may have raced with new irq work */
> =C2=A0		if (test_irq_work_pending())
> @@ -534,7 +535,7 @@ void timer_interrupt(struct pt_regs * regs)
> =C2=A0	/* Ensure a positive value is written to the decrementer, or else
> =C2=A0	=C2=A0* some CPUs will continue to take decrementer exceptions.
> =C2=A0	=C2=A0*/
> -	set_dec(DECREMENTER_MAX);
> +	set_dec(decrementer_max);
> =C2=A0
> =C2=A0	/* Some implementations of hotplug will get timer interrupts while
> =C2=A0	=C2=A0* offline, just ignore these and we also need to set
> @@ -582,9 +583,9 @@ static void generic_suspend_disable_irqs(void)
> =C2=A0	=C2=A0* with suspending.
> =C2=A0	=C2=A0*/
> =C2=A0
> -	set_dec(DECREMENTER_MAX);
> +	set_dec(decrementer_max);
> =C2=A0	local_irq_disable();
> -	set_dec(DECREMENTER_MAX);
> +	set_dec(decrementer_max);
> =C2=A0}
> =C2=A0
> =C2=A0static void generic_suspend_enable_irqs(void)
> @@ -865,7 +866,7 @@ static int decrementer_set_next_event(unsigned long e=
vt,
> =C2=A0
> =C2=A0static int decrementer_shutdown(struct clock_event_device *dev)
> =C2=A0{
> -	decrementer_set_next_event(DECREMENTER_MAX, dev);
> +	decrementer_set_next_event(decrementer_max, dev);
> =C2=A0	return 0;
> =C2=A0}
> =C2=A0
> @@ -891,6 +892,76 @@ static void register_decrementer_clockevent(int cpu)
> =C2=A0	clockevents_register_device(dec);
> =C2=A0}
> =C2=A0
> +static inline bool cpu_has_large_dec(void)
> +{
> +	return cpu_has_feature(CPU_FTR_ARCH_300);
> +}
> +
> +static inline bool large_dec_enabled(void)
> +{
> +	return (mfspr(SPRN_LPCR) & LPCR_LD) =3D=3D LPCR_LD;
> +}
> +
> +/* enables the large decrementer for the current CPU */
> +static void enable_large_decrementer(void)
> +{
> +	/* do we have a large decrementer? */
> +	if (!cpu_has_large_dec())
> +		return;
> +
> +	/* do we need a large decrementer? */
> +	if (decrementer_max <=3D DECREMENTER_DEFAULT_MAX)
> +		return;
> +
> +	mtspr(SPRN_LPCR, mfspr(SPRN_LPCR) | LPCR_LD);
> +
> +	if (!large_dec_enabled()) {
> +		decrementer_max =3D DECREMENTER_DEFAULT_MAX;
> +
> +		pr_warn("time_init: Failed to enable large decrementer on CPU %d\n",
> +			smp_processor_id());

Can you make this pr_warn_once() since every CPU is going to call this?

> +	}
> +}
> +
> +static void __init set_decrementer_max(void)
> +{
> +	struct device_node *cpu;
> +	const __be32 *fp;
> +	u64 bits =3D 32;
> +
> +	cpu =3D of_find_node_by_type(NULL, "cpu");
> +	if (cpu)
> +		fp =3D of_get_property(cpu, "ibm,dec-bits", NULL);
> +
> +	if (cpu && fp) {
> +		u64 dt_bits =3D of_read_number(fp, 1);
> +
> +		bits =3D dt_bits;
> +		if (bits > 64)
> +			bits =3D 64;
> +		else if (bits < 32)
> +			bits =3D 32;
> +
> +		WARN(bits !=3D dt_bits, "firmware supplied invalid ibm,dec-bits");
> +
> +		/*
> +		=C2=A0* Firmware says we support large dec but this cpu doesn't we
> +		=C2=A0* should warn about it. We can still limp along with default
> +		=C2=A0* 32 bit dec, but something is broken.
> +		=C2=A0*/
> +		if (!cpu_has_large_dec()) {
> +			WARN_ON(bits > 32);
> +			bits =3D 32;
> +		}
> +
> +		/* calculate the signed maximum given this many bits */
> +		decrementer_max =3D (1ul << (bits - 1)) - 1;
> +	}
> +
> +	pr_info("time_init: %llu bit decrementer (max: %llx)\n",
> +		bits, decrementer_max);
> +}
> +
> =C2=A0static void __init init_decrementer_clockevent(void)
> =C2=A0{
> =C2=A0	int cpu =3D smp_processor_id();
> @@ -898,7 +969,7 @@ static void __init init_decrementer_clockevent(void)
> =C2=A0	clockevents_calc_mult_shift(&decrementer_clockevent, ppc_tb_freq, =
4);
> =C2=A0
> =C2=A0	decrementer_clockevent.max_delta_ns =3D
> -		clockevent_delta2ns(DECREMENTER_MAX, &decrementer_clockevent);
> +		clockevent_delta2ns(decrementer_max, &decrementer_clockevent);
> =C2=A0	decrementer_clockevent.min_delta_ns =3D
> =C2=A0		clockevent_delta2ns(2, &decrementer_clockevent);
> =C2=A0
> @@ -907,6 +978,9 @@ static void __init init_decrementer_clockevent(void)
> =C2=A0
> =C2=A0void secondary_cpu_time_init(void)
> =C2=A0{
> +	/* Enable the large decrementer (if we need to) */
> +	enable_large_decrementer();
> +
> =C2=A0	/* Start the decrementer on CPUs that have manual control
> =C2=A0	=C2=A0* such as BookE
> =C2=A0	=C2=A0*/
> @@ -972,6 +1046,10 @@ void __init time_init(void)
> =C2=A0	vdso_data->tb_update_count =3D 0;
> =C2=A0	vdso_data->tb_ticks_per_sec =3D tb_ticks_per_sec;
> =C2=A0
> +	/* initialise and enable the large decrementer (if we have one) */
> +	set_decrementer_max();
> +	enable_large_decrementer();
> +
> =C2=A0	/* Start the decrementer on CPUs that have manual control
> =C2=A0	=C2=A0* such as BookE
> =C2=A0	=C2=A0*/

^ permalink raw reply	[flat|nested] 8+ messages in thread
end of thread, other threads:[~2016-06-03  2:02 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2016-04-12  4:38 [PATCH 1/2] powerpc/timer - large decrementer support Oliver O'Halloran
2016-04-12  4:38 ` [PATCH 2/2] KVM: PPC: hypervisor " Oliver O'Halloran
2016-04-12  4:53   ` kbuild test robot
2016-04-12  7:35   ` Balbir Singh
2016-04-12  7:19 ` [PATCH 1/2] powerpc/timer - " Balbir Singh
  -- strict thread matches above, loose matches on Subject: below --
2016-05-31  6:25 [PATCH v3 " Michael Neuling
2016-05-31  7:16 ` [PATCH " Oliver O'Halloran
2016-06-01  5:28   ` Michael Neuling
2016-06-03  2:01     ` Balbir Singh

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