[PATCH] clocksource: riscv_timer: Provide sched_clock

[PATCH] clocksource: riscv_timer: Provide sched_clock

[Anup Patel]

Currently, we don't have a sched_clock registered for RISC-V systems.
This means Linux time keeping will use jiffies (running at HZ) as the
default sched_clock.

To avoid this, we explicity provide sched_clock using RISC-V rdtime
instruction (similar to riscv_timer clocksource).

Signed-off-by: Anup Patel <anup@brainfault.org>
---
 drivers/clocksource/riscv_timer.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/clocksource/riscv_timer.c b/drivers/clocksource/riscv_timer.c
index 084e97dc10ed..431892200a08 100644
--- a/drivers/clocksource/riscv_timer.c
+++ b/drivers/clocksource/riscv_timer.c
@@ -8,6 +8,7 @@
 #include <linux/cpu.h>
 #include <linux/delay.h>
 #include <linux/irq.h>
+#include <linux/sched_clock.h>
 #include <asm/smp.h>
 #include <asm/sbi.h>
 
@@ -49,6 +50,11 @@ static unsigned long long riscv_clocksource_rdtime(struct clocksource *cs)
 	return get_cycles64();
 }
 
+static u64 riscv_sched_clock(void)
+{
+	return get_cycles64();
+}
+
 static DEFINE_PER_CPU(struct clocksource, riscv_clocksource) = {
 	.name		= "riscv_clocksource",
 	.rating		= 300,
@@ -97,6 +103,9 @@ static int __init riscv_timer_init_dt(struct device_node *n)
 	cs = per_cpu_ptr(&riscv_clocksource, cpuid);
 	clocksource_register_hz(cs, riscv_timebase);
 
+	sched_clock_register(riscv_sched_clock,
+			BITS_PER_LONG, riscv_timebase);
+
 	error = cpuhp_setup_state(CPUHP_AP_RISCV_TIMER_STARTING,
 			 "clockevents/riscv/timer:starting",
 			 riscv_timer_starting_cpu, riscv_timer_dying_cpu);
-- 
2.17.1

Re: [PATCH] clocksource: riscv_timer: Provide sched_clock

[Daniel Lezcano]

On 03/12/2018 13:35, Anup Patel wrote:
> Currently, we don't have a sched_clock registered for RISC-V systems.
> This means Linux time keeping will use jiffies (running at HZ) as the
> default sched_clock.
> 
> To avoid this, we explicity provide sched_clock using RISC-V rdtime
> instruction (similar to riscv_timer clocksource).
> 
> Signed-off-by: Anup Patel <anup@brainfault.org>

Hi Anup,

the GENERIC_SCHED_CLOCK dependency in the Kconfig is missing.

Thanks

> ---
>  drivers/clocksource/riscv_timer.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/clocksource/riscv_timer.c b/drivers/clocksource/riscv_timer.c
> index 084e97dc10ed..431892200a08 100644
> --- a/drivers/clocksource/riscv_timer.c
> +++ b/drivers/clocksource/riscv_timer.c
> @@ -8,6 +8,7 @@
>  #include <linux/cpu.h>
>  #include <linux/delay.h>
>  #include <linux/irq.h>
> +#include <linux/sched_clock.h>
>  #include <asm/smp.h>
>  #include <asm/sbi.h>
>  
> @@ -49,6 +50,11 @@ static unsigned long long riscv_clocksource_rdtime(struct clocksource *cs)
>  	return get_cycles64();
>  }
>  
> +static u64 riscv_sched_clock(void)
> +{
> +	return get_cycles64();
> +}
> +
>  static DEFINE_PER_CPU(struct clocksource, riscv_clocksource) = {
>  	.name		= "riscv_clocksource",
>  	.rating		= 300,
> @@ -97,6 +103,9 @@ static int __init riscv_timer_init_dt(struct device_node *n)
>  	cs = per_cpu_ptr(&riscv_clocksource, cpuid);
>  	clocksource_register_hz(cs, riscv_timebase);
>  
> +	sched_clock_register(riscv_sched_clock,
> +			BITS_PER_LONG, riscv_timebase);
> +
>  	error = cpuhp_setup_state(CPUHP_AP_RISCV_TIMER_STARTING,
>  			 "clockevents/riscv/timer:starting",
>  			 riscv_timer_starting_cpu, riscv_timer_dying_cpu);
> 


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Re: [PATCH] clocksource: riscv_timer: Provide sched_clock

[Anup Patel]

On Mon, Dec 3, 2018 at 6:29 PM Daniel Lezcano <daniel.lezcano@linaro.org> wrote:
>
> On 03/12/2018 13:35, Anup Patel wrote:
> > Currently, we don't have a sched_clock registered for RISC-V systems.
> > This means Linux time keeping will use jiffies (running at HZ) as the
> > default sched_clock.
> >
> > To avoid this, we explicity provide sched_clock using RISC-V rdtime
> > instruction (similar to riscv_timer clocksource).
> >
> > Signed-off-by: Anup Patel <anup@brainfault.org>
>
> Hi Anup,
>
> the GENERIC_SCHED_CLOCK dependency in the Kconfig is missing.

Sure, will do.

I also have another patch to select GENERIC_SCHED_CLOCK
for CONFIG_RISCV. Should I squash that patch with this patch??

Regards,
Anup

Re: [PATCH] clocksource: riscv_timer: Provide sched_clock

[Daniel Lezcano]

On 03/12/2018 15:50, Anup Patel wrote:
> On Mon, Dec 3, 2018 at 6:29 PM Daniel Lezcano <daniel.lezcano@linaro.org> wrote:
>>
>> On 03/12/2018 13:35, Anup Patel wrote:
>>> Currently, we don't have a sched_clock registered for RISC-V systems.
>>> This means Linux time keeping will use jiffies (running at HZ) as the
>>> default sched_clock.
>>>
>>> To avoid this, we explicity provide sched_clock using RISC-V rdtime
>>> instruction (similar to riscv_timer clocksource).
>>>
>>> Signed-off-by: Anup Patel <anup@brainfault.org>
>>
>> Hi Anup,
>>
>> the GENERIC_SCHED_CLOCK dependency in the Kconfig is missing.
> 
> Sure, will do.
> 
> I also have another patch to select GENERIC_SCHED_CLOCK
> for CONFIG_RISCV. Should I squash that patch with this patch??

I prefer the riscv config option to be merged via the riscv tree.


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Re: [PATCH] clocksource: riscv_timer: Provide sched_clock

[Palmer Dabbelt]

On Mon, 03 Dec 2018 04:35:24 PST (-0800), anup@brainfault.org wrote:
> Currently, we don't have a sched_clock registered for RISC-V systems.
> This means Linux time keeping will use jiffies (running at HZ) as the
> default sched_clock.
>
> To avoid this, we explicity provide sched_clock using RISC-V rdtime
> instruction (similar to riscv_timer clocksource).
>
> Signed-off-by: Anup Patel <anup@brainfault.org>
> ---
>  drivers/clocksource/riscv_timer.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/drivers/clocksource/riscv_timer.c b/drivers/clocksource/riscv_timer.c
> index 084e97dc10ed..431892200a08 100644
> --- a/drivers/clocksource/riscv_timer.c
> +++ b/drivers/clocksource/riscv_timer.c
> @@ -8,6 +8,7 @@
>  #include <linux/cpu.h>
>  #include <linux/delay.h>
>  #include <linux/irq.h>
> +#include <linux/sched_clock.h>
>  #include <asm/smp.h>
>  #include <asm/sbi.h>
>
> @@ -49,6 +50,11 @@ static unsigned long long riscv_clocksource_rdtime(struct clocksource *cs)
>  	return get_cycles64();
>  }
>
> +static u64 riscv_sched_clock(void)
> +{
> +	return get_cycles64();
> +}
> +
>  static DEFINE_PER_CPU(struct clocksource, riscv_clocksource) = {
>  	.name		= "riscv_clocksource",
>  	.rating		= 300,
> @@ -97,6 +103,9 @@ static int __init riscv_timer_init_dt(struct device_node *n)
>  	cs = per_cpu_ptr(&riscv_clocksource, cpuid);
>  	clocksource_register_hz(cs, riscv_timebase);
>
> +	sched_clock_register(riscv_sched_clock,
> +			BITS_PER_LONG, riscv_timebase);

Shouldn't this just be 64, not BITS_PER_LONG?  We have 64-bit counters on 
RV32I.

> +
>  	error = cpuhp_setup_state(CPUHP_AP_RISCV_TIMER_STARTING,
>  			 "clockevents/riscv/timer:starting",
>  			 riscv_timer_starting_cpu, riscv_timer_dying_cpu);

Re: [PATCH] clocksource: riscv_timer: Provide sched_clock

[Anup Patel]

On Fri, Dec 7, 2018 at 2:02 AM Palmer Dabbelt <palmer@sifive.com> wrote:
>
> On Mon, 03 Dec 2018 04:35:24 PST (-0800), anup@brainfault.org wrote:
> > Currently, we don't have a sched_clock registered for RISC-V systems.
> > This means Linux time keeping will use jiffies (running at HZ) as the
> > default sched_clock.
> >
> > To avoid this, we explicity provide sched_clock using RISC-V rdtime
> > instruction (similar to riscv_timer clocksource).
> >
> > Signed-off-by: Anup Patel <anup@brainfault.org>
> > ---
> >  drivers/clocksource/riscv_timer.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> >
> > diff --git a/drivers/clocksource/riscv_timer.c b/drivers/clocksource/riscv_timer.c
> > index 084e97dc10ed..431892200a08 100644
> > --- a/drivers/clocksource/riscv_timer.c
> > +++ b/drivers/clocksource/riscv_timer.c
> > @@ -8,6 +8,7 @@
> >  #include <linux/cpu.h>
> >  #include <linux/delay.h>
> >  #include <linux/irq.h>
> > +#include <linux/sched_clock.h>
> >  #include <asm/smp.h>
> >  #include <asm/sbi.h>
> >
> > @@ -49,6 +50,11 @@ static unsigned long long riscv_clocksource_rdtime(struct clocksource *cs)
> >       return get_cycles64();
> >  }
> >
> > +static u64 riscv_sched_clock(void)
> > +{
> > +     return get_cycles64();
> > +}
> > +
> >  static DEFINE_PER_CPU(struct clocksource, riscv_clocksource) = {
> >       .name           = "riscv_clocksource",
> >       .rating         = 300,
> > @@ -97,6 +103,9 @@ static int __init riscv_timer_init_dt(struct device_node *n)
> >       cs = per_cpu_ptr(&riscv_clocksource, cpuid);
> >       clocksource_register_hz(cs, riscv_timebase);
> >
> > +     sched_clock_register(riscv_sched_clock,
> > +                     BITS_PER_LONG, riscv_timebase);
>
> Shouldn't this just be 64, not BITS_PER_LONG?  We have 64-bit counters on
> RV32I.

Ahh, yes. I got mislead by "mask" field of clocksource.

I will change this to 64 and add another patch on fix "mask" of
clocksource as well.

Regards,
Anup