[PATCH v5 0/3] Improve CLOCK_EVT_FEAT_C3STOP feature setting

[PATCH v5 0/3] Improve CLOCK_EVT_FEAT_C3STOP feature setting

[Anup Patel]

This series improves the RISC-V timer driver to set CLOCK_EVT_FEAT_C3STOP
feature based on RISC-V platform capabilities.

These patches can also be found in riscv_timer_dt_imp_v5 branch at:
https://github.com/avpatel/linux.git

Changes since v4:
 - Update commit text of PATCH1 based on Samuel's comments
 - Renamed DT property "riscv,timer-can-wake-cpu" to
   "riscv,timer-cannot-wake-cpu" in PATCH2 and PATCH3
 - Updated description of DT property "riscv,timer-cannot-wake-cpu"
   in PATCH2

Changes since v3:
 - Rebased on Linux-6.1-rc7
 - Replaced PATCH1 with a patch to initialize broadcast timer

Changes since v2:
 - Include Conor's revert patch as the first patch and rebased other patches
 - Update PATCH2 to document bindings for separate RISC-V timer DT node
 - Update PATCH3 based on RISC-V timer DT node bindings

Changes since v1:
 - Rebased on Linux-5.19-rc8
 - Renamed "riscv,always-on" DT property to "riscv,timer-can-wake-cpu"

Anup Patel (2):
  dt-bindings: timer: Add bindings for the RISC-V timer device
  clocksource: timer-riscv: Set CLOCK_EVT_FEAT_C3STOP based on DT

Conor Dooley (1):
  RISC-V: time: initialize hrtimer based broadcast clock event device

 .../bindings/timer/riscv,timer.yaml           | 52 +++++++++++++++++++
 arch/riscv/kernel/time.c                      |  3 ++
 drivers/clocksource/timer-riscv.c             | 12 ++++-
 3 files changed, 66 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/devicetree/bindings/timer/riscv,timer.yaml

-- 
2.34.1

[PATCH v5 1/3] RISC-V: time: initialize hrtimer based broadcast clock event device

[Anup Patel]

From: Conor Dooley <conor.dooley@microchip.com>

Similarly to commit 022eb8ae8b5e ("ARM: 8938/1: kernel: initialize
broadcast hrtimer based clock event device"), RISC-V needs to initiate
hrtimer based broadcast clock event device before C3STOP can be used.
Otherwise, the introduction of C3STOP for the RISC-V arch timer in
commit 232ccac1bd9b ("clocksource/drivers/riscv: Events are stopped
during CPU suspend") leaves us without any broadcast timer registered.
This prevents the kernel from entering oneshot mode, which breaks timer
behaviour, for example clock_nanosleep().

A test app that sleeps each cpu for 6, 5, 4, 3 ms respectively, HZ=250
& C3STOP enabled, the sleep times are rounded up to the next jiffy:
== CPU: 1 ==      == CPU: 2 ==      == CPU: 3 ==      == CPU: 4 ==
Mean: 7.974992    Mean: 7.976534    Mean: 7.962591    Mean: 3.952179
Std Dev: 0.154374 Std Dev: 0.156082 Std Dev: 0.171018 Std Dev: 0.076193
Hi: 9.472000      Hi: 10.495000     Hi: 8.864000      Hi: 4.736000
Lo: 6.087000      Lo: 6.380000      Lo: 4.872000      Lo: 3.403000
Samples: 521      Samples: 521      Samples: 521      Samples: 521

Link: https://lore.kernel.org/linux-riscv/YzYTNQRxLr7Q9JR0@spud/
Fixes: 232ccac1bd9b ("clocksource/drivers/riscv: Events are stopped during CPU suspend")
Suggested-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Samuel Holland <samuel@sholland.org>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
---
 arch/riscv/kernel/time.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/riscv/kernel/time.c b/arch/riscv/kernel/time.c
index 8217b0f67c6c..1cf21db4fcc7 100644
--- a/arch/riscv/kernel/time.c
+++ b/arch/riscv/kernel/time.c
@@ -5,6 +5,7 @@
  */
 
 #include <linux/of_clk.h>
+#include <linux/clockchips.h>
 #include <linux/clocksource.h>
 #include <linux/delay.h>
 #include <asm/sbi.h>
@@ -29,6 +30,8 @@ void __init time_init(void)
 
 	of_clk_init(NULL);
 	timer_probe();
+
+	tick_setup_hrtimer_broadcast();
 }
 
 void clocksource_arch_init(struct clocksource *cs)
-- 
2.34.1

Re: [PATCH v5 1/3] RISC-V: time: initialize hrtimer based broadcast clock event device

[Conor Dooley]

On 1 December 2022 12:39:52 GMT, Anup Patel <apatel@ventanamicro.com> wrote:
>From: Conor Dooley <conor.dooley@microchip.com>
>
>Similarly to commit 022eb8ae8b5e ("ARM: 8938/1: kernel: initialize
>broadcast hrtimer based clock event device"), RISC-V needs to initiate
>hrtimer based broadcast clock event device before C3STOP can be used.
>Otherwise, the introduction of C3STOP for the RISC-V arch timer in
>commit 232ccac1bd9b ("clocksource/drivers/riscv: Events are stopped
>during CPU suspend") leaves us without any broadcast timer registered.
>This prevents the kernel from entering oneshot mode, which breaks timer
>behaviour, for example clock_nanosleep().
>
>A test app that sleeps each cpu for 6, 5, 4, 3 ms respectively, HZ=250
>& C3STOP enabled, the sleep times are rounded up to the next jiffy:
>== CPU: 1 ==      == CPU: 2 ==      == CPU: 3 ==      == CPU: 4 ==
>Mean: 7.974992    Mean: 7.976534    Mean: 7.962591    Mean: 3.952179
>Std Dev: 0.154374 Std Dev: 0.156082 Std Dev: 0.171018 Std Dev: 0.076193
>Hi: 9.472000      Hi: 10.495000     Hi: 8.864000      Hi: 4.736000
>Lo: 6.087000      Lo: 6.380000      Lo: 4.872000      Lo: 3.403000
>Samples: 521      Samples: 521      Samples: 521      Samples: 521
>
>Link: https://lore.kernel.org/linux-riscv/YzYTNQRxLr7Q9JR0@spud/
>Fixes: 232ccac1bd9b ("clocksource/drivers/riscv: Events are stopped during CPU suspend")
>Suggested-by: Samuel Holland <samuel@sholland.org>
>Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
>Reviewed-by: Samuel Holland <samuel@sholland.org>
>Acked-by: Palmer Dabbelt <palmer@rivosinc.com>

Huh, thought I replied already but I just have forgotten to...
Since you've added this patch to your series,  it needs your SoB appended.

Thanks,
Conor.

>---
> arch/riscv/kernel/time.c | 3 +++
> 1 file changed, 3 insertions(+)
>
>diff --git a/arch/riscv/kernel/time.c b/arch/riscv/kernel/time.c
>index 8217b0f67c6c..1cf21db4fcc7 100644
>--- a/arch/riscv/kernel/time.c
>+++ b/arch/riscv/kernel/time.c
>@@ -5,6 +5,7 @@
>  */
> 
> #include <linux/of_clk.h>
>+#include <linux/clockchips.h>
> #include <linux/clocksource.h>
> #include <linux/delay.h>
> #include <asm/sbi.h>
>@@ -29,6 +30,8 @@ void __init time_init(void)
> 
> 	of_clk_init(NULL);
> 	timer_probe();
>+
>+	tick_setup_hrtimer_broadcast();
> }
> 
> void clocksource_arch_init(struct clocksource *cs)

[PATCH v5 2/3] dt-bindings: timer: Add bindings for the RISC-V timer device

[Anup Patel]

We add DT bindings for a separate RISC-V timer DT node which can
be used to describe implementation specific behaviour (such as
timer interrupt not triggered during non-retentive suspend).

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
---
 .../bindings/timer/riscv,timer.yaml           | 52 +++++++++++++++++++
 1 file changed, 52 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/timer/riscv,timer.yaml

diff --git a/Documentation/devicetree/bindings/timer/riscv,timer.yaml b/Documentation/devicetree/bindings/timer/riscv,timer.yaml
new file mode 100644
index 000000000000..38d67e1a5a79
--- /dev/null
+++ b/Documentation/devicetree/bindings/timer/riscv,timer.yaml
@@ -0,0 +1,52 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/timer/riscv,timer.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: RISC-V timer
+
+maintainers:
+  - Anup Patel <anup@brainfault.org>
+
+description: |+
+  RISC-V platforms always have a RISC-V timer device for the supervisor-mode
+  based on the time CSR defined by the RISC-V privileged specification. The
+  timer interrupts of this device are configured using the RISC-V SBI Time
+  extension or the RISC-V Sstc extension.
+
+  The clock frequency of RISC-V timer device is specified via the
+  "timebase-frequency" DT property of "/cpus" DT node which is described
+  in Documentation/devicetree/bindings/riscv/cpus.yaml
+
+properties:
+  compatible:
+    enum:
+      - riscv,timer
+
+  interrupts-extended:
+    minItems: 1
+    maxItems: 4096   # Should be enough?
+
+  riscv,timer-cannot-wake-cpu:
+    type: boolean
+    description:
+      If present, the timer interrupt cannot wake up the CPU from one or
+      more suspend/idle states.
+
+additionalProperties: false
+
+required:
+  - compatible
+  - interrupts-extended
+
+examples:
+  - |
+    timer {
+      compatible = "riscv,timer";
+      interrupts-extended = <&cpu1intc 5>,
+                            <&cpu2intc 5>,
+                            <&cpu3intc 5>,
+                            <&cpu4intc 5>;
+    };
+...
-- 
2.34.1

Re: [PATCH v5 2/3] dt-bindings: timer: Add bindings for the RISC-V timer device

[Rob Herring]

On Thu, 01 Dec 2022 18:09:53 +0530, Anup Patel wrote:
> We add DT bindings for a separate RISC-V timer DT node which can
> be used to describe implementation specific behaviour (such as
> timer interrupt not triggered during non-retentive suspend).
> 
> Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
> Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
> ---
>  .../bindings/timer/riscv,timer.yaml           | 52 +++++++++++++++++++
>  1 file changed, 52 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/timer/riscv,timer.yaml
> 

Reviewed-by: Rob Herring <robh@kernel.org>

[PATCH v5 3/3] clocksource: timer-riscv: Set CLOCK_EVT_FEAT_C3STOP based on DT

[Anup Patel]

We should set CLOCK_EVT_FEAT_C3STOP for a clock_event_device only
when riscv,timer-cannot-wake-cpu DT property is present in the RISC-V
timer DT node.

This way CLOCK_EVT_FEAT_C3STOP feature is set for clock_event_device
based on RISC-V platform capabilities rather than having it set for
all RISC-V platforms.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
---
 drivers/clocksource/timer-riscv.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
index 969a552da8d2..1b4b36df5484 100644
--- a/drivers/clocksource/timer-riscv.c
+++ b/drivers/clocksource/timer-riscv.c
@@ -28,6 +28,7 @@
 #include <asm/timex.h>
 
 static DEFINE_STATIC_KEY_FALSE(riscv_sstc_available);
+static bool riscv_timer_cannot_wake_cpu;
 
 static int riscv_clock_next_event(unsigned long delta,
 		struct clock_event_device *ce)
@@ -51,7 +52,7 @@ static int riscv_clock_next_event(unsigned long delta,
 static unsigned int riscv_clock_event_irq;
 static DEFINE_PER_CPU(struct clock_event_device, riscv_clock_event) = {
 	.name			= "riscv_timer_clockevent",
-	.features		= CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_C3STOP,
+	.features		= CLOCK_EVT_FEAT_ONESHOT,
 	.rating			= 100,
 	.set_next_event		= riscv_clock_next_event,
 };
@@ -85,6 +86,8 @@ static int riscv_timer_starting_cpu(unsigned int cpu)
 
 	ce->cpumask = cpumask_of(cpu);
 	ce->irq = riscv_clock_event_irq;
+	if (riscv_timer_cannot_wake_cpu)
+		ce->features |= CLOCK_EVT_FEAT_C3STOP;
 	clockevents_config_and_register(ce, riscv_timebase, 100, 0x7fffffff);
 
 	enable_percpu_irq(riscv_clock_event_irq,
@@ -139,6 +142,13 @@ static int __init riscv_timer_init_dt(struct device_node *n)
 	if (cpuid != smp_processor_id())
 		return 0;
 
+	child = of_find_compatible_node(NULL, NULL, "riscv,timer");
+	if (child) {
+		riscv_timer_cannot_wake_cpu = of_property_read_bool(child,
+					"riscv,timer-cannot-wake-cpu");
+		of_node_put(child);
+	}
+
 	domain = NULL;
 	child = of_get_compatible_child(n, "riscv,cpu-intc");
 	if (!child) {
-- 
2.34.1

Re: [PATCH v5 3/3] clocksource: timer-riscv: Set CLOCK_EVT_FEAT_C3STOP based on DT

[Rob Herring]

On Thu, Dec 01, 2022 at 06:09:54PM +0530, Anup Patel wrote:
> We should set CLOCK_EVT_FEAT_C3STOP for a clock_event_device only
> when riscv,timer-cannot-wake-cpu DT property is present in the RISC-V
> timer DT node.
> 
> This way CLOCK_EVT_FEAT_C3STOP feature is set for clock_event_device
> based on RISC-V platform capabilities rather than having it set for
> all RISC-V platforms.
> 
> Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
> Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
> ---
>  drivers/clocksource/timer-riscv.c | 12 +++++++++++-
>  1 file changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
> index 969a552da8d2..1b4b36df5484 100644
> --- a/drivers/clocksource/timer-riscv.c
> +++ b/drivers/clocksource/timer-riscv.c
> @@ -28,6 +28,7 @@
>  #include <asm/timex.h>
>  
>  static DEFINE_STATIC_KEY_FALSE(riscv_sstc_available);
> +static bool riscv_timer_cannot_wake_cpu;
>  
>  static int riscv_clock_next_event(unsigned long delta,
>  		struct clock_event_device *ce)
> @@ -51,7 +52,7 @@ static int riscv_clock_next_event(unsigned long delta,
>  static unsigned int riscv_clock_event_irq;
>  static DEFINE_PER_CPU(struct clock_event_device, riscv_clock_event) = {
>  	.name			= "riscv_timer_clockevent",
> -	.features		= CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_C3STOP,
> +	.features		= CLOCK_EVT_FEAT_ONESHOT,

A platform that depended on CLOCK_EVT_FEAT_C3STOP being set will break 
with this change because its existing DT will not have the new property.

It needs to be the other way around which would effectively be the 
existing 'always-on' property. 

>  	.rating			= 100,
>  	.set_next_event		= riscv_clock_next_event,
>  };
> @@ -85,6 +86,8 @@ static int riscv_timer_starting_cpu(unsigned int cpu)
>  
>  	ce->cpumask = cpumask_of(cpu);
>  	ce->irq = riscv_clock_event_irq;
> +	if (riscv_timer_cannot_wake_cpu)
> +		ce->features |= CLOCK_EVT_FEAT_C3STOP;
>  	clockevents_config_and_register(ce, riscv_timebase, 100, 0x7fffffff);
>  
>  	enable_percpu_irq(riscv_clock_event_irq,
> @@ -139,6 +142,13 @@ static int __init riscv_timer_init_dt(struct device_node *n)
>  	if (cpuid != smp_processor_id())
>  		return 0;
>  
> +	child = of_find_compatible_node(NULL, NULL, "riscv,timer");
> +	if (child) {
> +		riscv_timer_cannot_wake_cpu = of_property_read_bool(child,
> +					"riscv,timer-cannot-wake-cpu");
> +		of_node_put(child);
> +	}
> +
>  	domain = NULL;
>  	child = of_get_compatible_child(n, "riscv,cpu-intc");
>  	if (!child) {
> -- 
> 2.34.1
> 
> 

Re: [PATCH v5 3/3] clocksource: timer-riscv: Set CLOCK_EVT_FEAT_C3STOP based on DT

[Anup Patel]

On Fri, Dec 2, 2022 at 5:36 AM Rob Herring <robh@kernel.org> wrote:
>
> On Thu, Dec 01, 2022 at 06:09:54PM +0530, Anup Patel wrote:
> > We should set CLOCK_EVT_FEAT_C3STOP for a clock_event_device only
> > when riscv,timer-cannot-wake-cpu DT property is present in the RISC-V
> > timer DT node.
> >
> > This way CLOCK_EVT_FEAT_C3STOP feature is set for clock_event_device
> > based on RISC-V platform capabilities rather than having it set for
> > all RISC-V platforms.
> >
> > Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> > Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
> > Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
> > ---
> >  drivers/clocksource/timer-riscv.c | 12 +++++++++++-
> >  1 file changed, 11 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
> > index 969a552da8d2..1b4b36df5484 100644
> > --- a/drivers/clocksource/timer-riscv.c
> > +++ b/drivers/clocksource/timer-riscv.c
> > @@ -28,6 +28,7 @@
> >  #include <asm/timex.h>
> >
> >  static DEFINE_STATIC_KEY_FALSE(riscv_sstc_available);
> > +static bool riscv_timer_cannot_wake_cpu;
> >
> >  static int riscv_clock_next_event(unsigned long delta,
> >               struct clock_event_device *ce)
> > @@ -51,7 +52,7 @@ static int riscv_clock_next_event(unsigned long delta,
> >  static unsigned int riscv_clock_event_irq;
> >  static DEFINE_PER_CPU(struct clock_event_device, riscv_clock_event) = {
> >       .name                   = "riscv_timer_clockevent",
> > -     .features               = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_C3STOP,
> > +     .features               = CLOCK_EVT_FEAT_ONESHOT,
>
> A platform that depended on CLOCK_EVT_FEAT_C3STOP being set will break
> with this change because its existing DT will not have the new property.
>
> It needs to be the other way around which would effectively be the
> existing 'always-on' property.

There are no RISC-V platforms using C3STOP. The patch which
added C3STOP has been reverted.
(Refer, https://lore.kernel.org/lkml/a218ebf8-0fba-168d-6598-c970bbff5faf@sholland.org/T/)

I just need to rebase this patch upon the C3STOP revert patch.

>
> >       .rating                 = 100,
> >       .set_next_event         = riscv_clock_next_event,
> >  };
> > @@ -85,6 +86,8 @@ static int riscv_timer_starting_cpu(unsigned int cpu)
> >
> >       ce->cpumask = cpumask_of(cpu);
> >       ce->irq = riscv_clock_event_irq;
> > +     if (riscv_timer_cannot_wake_cpu)
> > +             ce->features |= CLOCK_EVT_FEAT_C3STOP;
> >       clockevents_config_and_register(ce, riscv_timebase, 100, 0x7fffffff);
> >
> >       enable_percpu_irq(riscv_clock_event_irq,
> > @@ -139,6 +142,13 @@ static int __init riscv_timer_init_dt(struct device_node *n)
> >       if (cpuid != smp_processor_id())
> >               return 0;
> >
> > +     child = of_find_compatible_node(NULL, NULL, "riscv,timer");
> > +     if (child) {
> > +             riscv_timer_cannot_wake_cpu = of_property_read_bool(child,
> > +                                     "riscv,timer-cannot-wake-cpu");
> > +             of_node_put(child);
> > +     }
> > +
> >       domain = NULL;
> >       child = of_get_compatible_child(n, "riscv,cpu-intc");
> >       if (!child) {
> > --
> > 2.34.1
> >
> >

Regards,
Anup

Re: [PATCH v5 3/3] clocksource: timer-riscv: Set CLOCK_EVT_FEAT_C3STOP based on DT

[Conor Dooley]

[-- Attachment #1: Type: text/plain, Size: 4260 bytes --]

Hey Rob, Anup, Prabhakar,

On Fri, Dec 02, 2022 at 12:03:05PM +0530, Anup Patel wrote:
> On Fri, Dec 2, 2022 at 5:36 AM Rob Herring <robh@kernel.org> wrote:
> >
> > On Thu, Dec 01, 2022 at 06:09:54PM +0530, Anup Patel wrote:
> > > We should set CLOCK_EVT_FEAT_C3STOP for a clock_event_device only
> > > when riscv,timer-cannot-wake-cpu DT property is present in the RISC-V
> > > timer DT node.
> > >
> > > This way CLOCK_EVT_FEAT_C3STOP feature is set for clock_event_device
> > > based on RISC-V platform capabilities rather than having it set for
> > > all RISC-V platforms.
> > >
> > > Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> > > Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
> > > Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
> > > ---
> > >  drivers/clocksource/timer-riscv.c | 12 +++++++++++-
> > >  1 file changed, 11 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
> > > index 969a552da8d2..1b4b36df5484 100644
> > > --- a/drivers/clocksource/timer-riscv.c
> > > +++ b/drivers/clocksource/timer-riscv.c
> > > @@ -28,6 +28,7 @@
> > >  #include <asm/timex.h>
> > >
> > >  static DEFINE_STATIC_KEY_FALSE(riscv_sstc_available);
> > > +static bool riscv_timer_cannot_wake_cpu;
> > >
> > >  static int riscv_clock_next_event(unsigned long delta,
> > >               struct clock_event_device *ce)
> > > @@ -51,7 +52,7 @@ static int riscv_clock_next_event(unsigned long delta,
> > >  static unsigned int riscv_clock_event_irq;
> > >  static DEFINE_PER_CPU(struct clock_event_device, riscv_clock_event) = {
> > >       .name                   = "riscv_timer_clockevent",
> > > -     .features               = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_C3STOP,
> > > +     .features               = CLOCK_EVT_FEAT_ONESHOT,
> >
> > A platform that depended on CLOCK_EVT_FEAT_C3STOP being set will break
> > with this change because its existing DT will not have the new property.
> >
> > It needs to be the other way around which would effectively be the
> > existing 'always-on' property.
> 
> There are no RISC-V platforms using C3STOP. The patch which
> added C3STOP has been reverted.
> (Refer, https://lore.kernel.org/lkml/a218ebf8-0fba-168d-6598-c970bbff5faf@sholland.org/T/)
> 
> I just need to rebase this patch upon the C3STOP revert patch.

I guess you could say that the C3STOP addition was done spec-ulatively*,
as the platform that actually exhibits that behaviour does not use the
riscv-timer & its maintainer acked the revert (allwinner d1 family).

*The spec does not make any guarantees about whether events arrive
during suspend, only the behaviour *if* they arrive.

Switching the property to "always-on" would require retrofitting that
property to every other existing platform (and therefore regressing some
behaviour there, no?).

Most of the existing platforms are "toys" or demo platforms though, so
it would not, I guess, be the end of the world to do so. Doubly so since
none of them actually implement any sleep states that making it an
"always-on" property.

I've said since the start that defaulting to C3STOP is the "safer" thing
to do, and although we disagreed on this last time Anup, I think the
better outcome of someone missing a DT property is inaccessible sleep
states rather than going into sleep states they cannot get out of.

For PolarFire SoC, which I guess is one of the few "commerical"
platforms, I'd be willing to accept retrofitting, since we have not yet
implemented such sleep states yet.

Maybe Prabhakar knows whether the RZ/Five has either a) implemented
sleep states and b) which side of the "timer events arrive in suspend"
divide their platform lies on.
I'm particular interested here since that is not a SiFive core complex.

I would like to get DT maintainer approval of an approach here soon-ish
so that we can something sorted for the jh7110 stuff and for the
bouffalolabs SoC - the latter of which may very well be in the "no
events in suspend" camp as it also uses thead stuff.

Sorry for kinda rowing back on my previous acceptance of the approach,
but I am really between two minds on this.

Thanks,
Conor.


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Re: [PATCH v5 3/3] clocksource: timer-riscv: Set CLOCK_EVT_FEAT_C3STOP based on DT

[Samuel Holland]

On 12/4/22 17:34, Conor Dooley wrote:
> Hey Rob, Anup, Prabhakar,
> 
> On Fri, Dec 02, 2022 at 12:03:05PM +0530, Anup Patel wrote:
>> On Fri, Dec 2, 2022 at 5:36 AM Rob Herring <robh@kernel.org> wrote:
>>>
>>> On Thu, Dec 01, 2022 at 06:09:54PM +0530, Anup Patel wrote:
>>>> We should set CLOCK_EVT_FEAT_C3STOP for a clock_event_device only
>>>> when riscv,timer-cannot-wake-cpu DT property is present in the RISC-V
>>>> timer DT node.
>>>>
>>>> This way CLOCK_EVT_FEAT_C3STOP feature is set for clock_event_device
>>>> based on RISC-V platform capabilities rather than having it set for
>>>> all RISC-V platforms.
>>>>
>>>> Signed-off-by: Anup Patel <apatel@ventanamicro.com>
>>>> Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
>>>> Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
>>>> ---
>>>>  drivers/clocksource/timer-riscv.c | 12 +++++++++++-
>>>>  1 file changed, 11 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
>>>> index 969a552da8d2..1b4b36df5484 100644
>>>> --- a/drivers/clocksource/timer-riscv.c
>>>> +++ b/drivers/clocksource/timer-riscv.c
>>>> @@ -28,6 +28,7 @@
>>>>  #include <asm/timex.h>
>>>>
>>>>  static DEFINE_STATIC_KEY_FALSE(riscv_sstc_available);
>>>> +static bool riscv_timer_cannot_wake_cpu;
>>>>
>>>>  static int riscv_clock_next_event(unsigned long delta,
>>>>               struct clock_event_device *ce)
>>>> @@ -51,7 +52,7 @@ static int riscv_clock_next_event(unsigned long delta,
>>>>  static unsigned int riscv_clock_event_irq;
>>>>  static DEFINE_PER_CPU(struct clock_event_device, riscv_clock_event) = {
>>>>       .name                   = "riscv_timer_clockevent",
>>>> -     .features               = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_C3STOP,
>>>> +     .features               = CLOCK_EVT_FEAT_ONESHOT,
>>>
>>> A platform that depended on CLOCK_EVT_FEAT_C3STOP being set will break
>>> with this change because its existing DT will not have the new property.
>>>
>>> It needs to be the other way around which would effectively be the
>>> existing 'always-on' property.
>>
>> There are no RISC-V platforms using C3STOP. The patch which
>> added C3STOP has been reverted.
>> (Refer, https://lore.kernel.org/lkml/a218ebf8-0fba-168d-6598-c970bbff5faf@sholland.org/T/)
>>
>> I just need to rebase this patch upon the C3STOP revert patch.
> 
> I guess you could say that the C3STOP addition was done spec-ulatively*,
> as the platform that actually exhibits that behaviour does not use the
> riscv-timer & its maintainer acked the revert (allwinner d1 family).

For clarity: that doesn't mean the platform will _never_ use the SBI
timer facility, just that Linux happens to not use it right now.

> *The spec does not make any guarantees about whether events arrive
> during suspend, only the behaviour *if* they arrive.
> 
> Switching the property to "always-on" would require retrofitting that
> property to every other existing platform (and therefore regressing some
> behaviour there, no?).
> 
> Most of the existing platforms are "toys" or demo platforms though, so
> it would not, I guess, be the end of the world to do so. Doubly so since
> none of them actually implement any sleep states that making it an
> "always-on" property.

Specifically, only sleep states with a "local-timer-stop" property would
be inhibited by the C3STOP flag, so there is only possibility of a
regression if some DT declaring such a sleep state exists anywhere.

Regards,
Samuel

> I've said since the start that defaulting to C3STOP is the "safer" thing
> to do, and although we disagreed on this last time Anup, I think the
> better outcome of someone missing a DT property is inaccessible sleep
> states rather than going into sleep states they cannot get out of.
> 
> For PolarFire SoC, which I guess is one of the few "commerical"
> platforms, I'd be willing to accept retrofitting, since we have not yet
> implemented such sleep states yet.
> 
> Maybe Prabhakar knows whether the RZ/Five has either a) implemented
> sleep states and b) which side of the "timer events arrive in suspend"
> divide their platform lies on.
> I'm particular interested here since that is not a SiFive core complex.
> 
> I would like to get DT maintainer approval of an approach here soon-ish
> so that we can something sorted for the jh7110 stuff and for the
> bouffalolabs SoC - the latter of which may very well be in the "no
> events in suspend" camp as it also uses thead stuff.
> 
> Sorry for kinda rowing back on my previous acceptance of the approach,
> but I am really between two minds on this.
> 
> Thanks,
> Conor.
> 

Re: [PATCH v5 3/3] clocksource: timer-riscv: Set CLOCK_EVT_FEAT_C3STOP based on DT

[Conor Dooley]

On Mon, Dec 05, 2022 at 02:17:40AM -0600, Samuel Holland wrote:
> On 12/4/22 17:34, Conor Dooley wrote:
> > Hey Rob, Anup, Prabhakar,
> > 
> > On Fri, Dec 02, 2022 at 12:03:05PM +0530, Anup Patel wrote:
> >> On Fri, Dec 2, 2022 at 5:36 AM Rob Herring <robh@kernel.org> wrote:
> >>>
> >>> On Thu, Dec 01, 2022 at 06:09:54PM +0530, Anup Patel wrote:
> >>>> We should set CLOCK_EVT_FEAT_C3STOP for a clock_event_device only
> >>>> when riscv,timer-cannot-wake-cpu DT property is present in the RISC-V
> >>>> timer DT node.
> >>>>
> >>>> This way CLOCK_EVT_FEAT_C3STOP feature is set for clock_event_device
> >>>> based on RISC-V platform capabilities rather than having it set for
> >>>> all RISC-V platforms.
> >>>>
> >>>> Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> >>>> Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
> >>>> Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
> >>>> ---
> >>>>  drivers/clocksource/timer-riscv.c | 12 +++++++++++-
> >>>>  1 file changed, 11 insertions(+), 1 deletion(-)
> >>>>
> >>>> diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
> >>>> index 969a552da8d2..1b4b36df5484 100644
> >>>> --- a/drivers/clocksource/timer-riscv.c
> >>>> +++ b/drivers/clocksource/timer-riscv.c
> >>>> @@ -28,6 +28,7 @@
> >>>>  #include <asm/timex.h>
> >>>>
> >>>>  static DEFINE_STATIC_KEY_FALSE(riscv_sstc_available);
> >>>> +static bool riscv_timer_cannot_wake_cpu;
> >>>>
> >>>>  static int riscv_clock_next_event(unsigned long delta,
> >>>>               struct clock_event_device *ce)
> >>>> @@ -51,7 +52,7 @@ static int riscv_clock_next_event(unsigned long delta,
> >>>>  static unsigned int riscv_clock_event_irq;
> >>>>  static DEFINE_PER_CPU(struct clock_event_device, riscv_clock_event) = {
> >>>>       .name                   = "riscv_timer_clockevent",
> >>>> -     .features               = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_C3STOP,
> >>>> +     .features               = CLOCK_EVT_FEAT_ONESHOT,
> >>>
> >>> A platform that depended on CLOCK_EVT_FEAT_C3STOP being set will break
> >>> with this change because its existing DT will not have the new property.
> >>>
> >>> It needs to be the other way around which would effectively be the
> >>> existing 'always-on' property.
> >>
> >> There are no RISC-V platforms using C3STOP. The patch which
> >> added C3STOP has been reverted.
> >> (Refer, https://lore.kernel.org/lkml/a218ebf8-0fba-168d-6598-c970bbff5faf@sholland.org/T/)
> >>
> >> I just need to rebase this patch upon the C3STOP revert patch.
> > 
> > I guess you could say that the C3STOP addition was done spec-ulatively*,
> > as the platform that actually exhibits that behaviour does not use the
> > riscv-timer & its maintainer acked the revert (allwinner d1 family).
> 
> For clarity: that doesn't mean the platform will _never_ use the SBI
> timer facility, just that Linux happens to not use it right now.

Yeah sorry - should have been a bit clearer there. There's a few other
SoCs about that are using the thead cores, so I'd be "worried" that they
share the timer behaviour but do not have an alternative like you do on
the D1. That's part of what's kinda given me cold feet on the current
approach.

> > *The spec does not make any guarantees about whether events arrive
> > during suspend, only the behaviour *if* they arrive.
> > 
> > Switching the property to "always-on" would require retrofitting that
> > property to every other existing platform (and therefore regressing some
> > behaviour there, no?).
> > 
> > Most of the existing platforms are "toys" or demo platforms though, so
> > it would not, I guess, be the end of the world to do so. Doubly so since
> > none of them actually implement any sleep states that making it an
> > "always-on" property.
> 
> Specifically, only sleep states with a "local-timer-stop" property would
> be inhibited by the C3STOP flag, so there is only possibility of a
> regression if some DT declaring such a sleep state exists anywhere.
> 
> Regards,
> Samuel
> 
> > I've said since the start that defaulting to C3STOP is the "safer" thing
> > to do, and although we disagreed on this last time Anup, I think the
> > better outcome of someone missing a DT property is inaccessible sleep
> > states rather than going into sleep states they cannot get out of.
> > 
> > For PolarFire SoC, which I guess is one of the few "commerical"
> > platforms, I'd be willing to accept retrofitting, since we have not yet
> > implemented such sleep states yet.
> > 
> > Maybe Prabhakar knows whether the RZ/Five has either a) implemented
> > sleep states and b) which side of the "timer events arrive in suspend"
> > divide their platform lies on.
> > I'm particular interested here since that is not a SiFive core complex.
> > 
> > I would like to get DT maintainer approval of an approach here soon-ish
> > so that we can something sorted for the jh7110 stuff and for the
> > bouffalolabs SoC - the latter of which may very well be in the "no
> > events in suspend" camp as it also uses thead stuff.
> > 
> > Sorry for kinda rowing back on my previous acceptance of the approach,
> > but I am really between two minds on this.
> > 
> > Thanks,
> > Conor.
> > 
> 
> 
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv

Re: [PATCH v5 3/3] clocksource: timer-riscv: Set CLOCK_EVT_FEAT_C3STOP based on DT

[Conor Dooley]

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Hey Anup (& Daniel++),

On Mon, Dec 05, 2022 at 08:33:53AM +0000, Conor Dooley wrote:
> On Mon, Dec 05, 2022 at 02:17:40AM -0600, Samuel Holland wrote:
> > On 12/4/22 17:34, Conor Dooley wrote:
> > > Hey Rob, Anup, Prabhakar,
> > > 
> > > On Fri, Dec 02, 2022 at 12:03:05PM +0530, Anup Patel wrote:
> > >> On Fri, Dec 2, 2022 at 5:36 AM Rob Herring <robh@kernel.org> wrote:
> > >>>
> > >>> On Thu, Dec 01, 2022 at 06:09:54PM +0530, Anup Patel wrote:
> > >>>> We should set CLOCK_EVT_FEAT_C3STOP for a clock_event_device only
> > >>>> when riscv,timer-cannot-wake-cpu DT property is present in the RISC-V
> > >>>> timer DT node.
> > >>>>
> > >>>> This way CLOCK_EVT_FEAT_C3STOP feature is set for clock_event_device
> > >>>> based on RISC-V platform capabilities rather than having it set for
> > >>>> all RISC-V platforms.
> > >>>>
> > >>>> Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> > >>>> Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
> > >>>> Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
> > >>>> ---
> > >>>>  drivers/clocksource/timer-riscv.c | 12 +++++++++++-
> > >>>>  1 file changed, 11 insertions(+), 1 deletion(-)
> > >>>>
> > >>>> diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
> > >>>> index 969a552da8d2..1b4b36df5484 100644
> > >>>> --- a/drivers/clocksource/timer-riscv.c
> > >>>> +++ b/drivers/clocksource/timer-riscv.c
> > >>>> @@ -28,6 +28,7 @@
> > >>>>  #include <asm/timex.h>
> > >>>>
> > >>>>  static DEFINE_STATIC_KEY_FALSE(riscv_sstc_available);
> > >>>> +static bool riscv_timer_cannot_wake_cpu;
> > >>>>
> > >>>>  static int riscv_clock_next_event(unsigned long delta,
> > >>>>               struct clock_event_device *ce)
> > >>>> @@ -51,7 +52,7 @@ static int riscv_clock_next_event(unsigned long delta,
> > >>>>  static unsigned int riscv_clock_event_irq;
> > >>>>  static DEFINE_PER_CPU(struct clock_event_device, riscv_clock_event) = {
> > >>>>       .name                   = "riscv_timer_clockevent",
> > >>>> -     .features               = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_C3STOP,
> > >>>> +     .features               = CLOCK_EVT_FEAT_ONESHOT,
> > >>>
> > >>> A platform that depended on CLOCK_EVT_FEAT_C3STOP being set will break
> > >>> with this change because its existing DT will not have the new property.
> > >>>
> > >>> It needs to be the other way around which would effectively be the
> > >>> existing 'always-on' property.
> > >>
> > >> There are no RISC-V platforms using C3STOP. The patch which
> > >> added C3STOP has been reverted.
> > >> (Refer, https://lore.kernel.org/lkml/a218ebf8-0fba-168d-6598-c970bbff5faf@sholland.org/T/)
> > >>
> > >> I just need to rebase this patch upon the C3STOP revert patch.
> > > 
> > > I guess you could say that the C3STOP addition was done spec-ulatively*,
> > > as the platform that actually exhibits that behaviour does not use the
> > > riscv-timer & its maintainer acked the revert (allwinner d1 family).
> > 
> > For clarity: that doesn't mean the platform will _never_ use the SBI
> > timer facility, just that Linux happens to not use it right now.
> 
> Yeah sorry - should have been a bit clearer there. There's a few other
> SoCs about that are using the thead cores, so I'd be "worried" that they
> share the timer behaviour but do not have an alternative like you do on
> the D1. That's part of what's kinda given me cold feet on the current
> approach.
> 
> > > *The spec does not make any guarantees about whether events arrive
> > > during suspend, only the behaviour *if* they arrive.
> > > 
> > > Switching the property to "always-on" would require retrofitting that
> > > property to every other existing platform (and therefore regressing some
> > > behaviour there, no?).
> > > 
> > > Most of the existing platforms are "toys" or demo platforms though, so
> > > it would not, I guess, be the end of the world to do so. Doubly so since
> > > none of them actually implement any sleep states that making it an
> > > "always-on" property.
> > 
> > Specifically, only sleep states with a "local-timer-stop" property would
> > be inhibited by the C3STOP flag, so there is only possibility of a
> > regression if some DT declaring such a sleep state exists anywhere.

What is the plan for this series? IIRC, a rebase was required on top of
the revert?
I'm not overly pushed either way at this point, I'd like to get this
C3STOP issue sorted out before more thead powered SoCs start showing up
with the same implementation issues.

I know it is the Christmas period so not expecting anything to actually
happen right away.

Thanks,
Conor.

> > > I've said since the start that defaulting to C3STOP is the "safer" thing
> > > to do, and although we disagreed on this last time Anup, I think the
> > > better outcome of someone missing a DT property is inaccessible sleep
> > > states rather than going into sleep states they cannot get out of.
> > > 
> > > For PolarFire SoC, which I guess is one of the few "commerical"
> > > platforms, I'd be willing to accept retrofitting, since we have not yet
> > > implemented such sleep states yet.
> > > 
> > > Maybe Prabhakar knows whether the RZ/Five has either a) implemented
> > > sleep states and b) which side of the "timer events arrive in suspend"
> > > divide their platform lies on.
> > > I'm particular interested here since that is not a SiFive core complex.
> > > 
> > > I would like to get DT maintainer approval of an approach here soon-ish
> > > so that we can something sorted for the jh7110 stuff and for the
> > > bouffalolabs SoC - the latter of which may very well be in the "no
> > > events in suspend" camp as it also uses thead stuff.
> > > 
> > > Sorry for kinda rowing back on my previous acceptance of the approach,
> > > but I am really between two minds on this.


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Re: [PATCH v5 3/3] clocksource: timer-riscv: Set CLOCK_EVT_FEAT_C3STOP based on DT

[Lad, Prabhakar]

Hi Conor,

On Sun, Dec 4, 2022 at 11:34 PM Conor Dooley <conor@kernel.org> wrote:
>
> Hey Rob, Anup, Prabhakar,
>
> On Fri, Dec 02, 2022 at 12:03:05PM +0530, Anup Patel wrote:
> > On Fri, Dec 2, 2022 at 5:36 AM Rob Herring <robh@kernel.org> wrote:
> > >
> > > On Thu, Dec 01, 2022 at 06:09:54PM +0530, Anup Patel wrote:
> > > > We should set CLOCK_EVT_FEAT_C3STOP for a clock_event_device only
> > > > when riscv,timer-cannot-wake-cpu DT property is present in the RISC-V
> > > > timer DT node.
> > > >
> > > > This way CLOCK_EVT_FEAT_C3STOP feature is set for clock_event_device
> > > > based on RISC-V platform capabilities rather than having it set for
> > > > all RISC-V platforms.
> > > >
> > > > Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> > > > Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
> > > > Acked-by: Palmer Dabbelt <palmer@rivosinc.com>
> > > > ---
> > > >  drivers/clocksource/timer-riscv.c | 12 +++++++++++-
> > > >  1 file changed, 11 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
> > > > index 969a552da8d2..1b4b36df5484 100644
> > > > --- a/drivers/clocksource/timer-riscv.c
> > > > +++ b/drivers/clocksource/timer-riscv.c
> > > > @@ -28,6 +28,7 @@
> > > >  #include <asm/timex.h>
> > > >
> > > >  static DEFINE_STATIC_KEY_FALSE(riscv_sstc_available);
> > > > +static bool riscv_timer_cannot_wake_cpu;
> > > >
> > > >  static int riscv_clock_next_event(unsigned long delta,
> > > >               struct clock_event_device *ce)
> > > > @@ -51,7 +52,7 @@ static int riscv_clock_next_event(unsigned long delta,
> > > >  static unsigned int riscv_clock_event_irq;
> > > >  static DEFINE_PER_CPU(struct clock_event_device, riscv_clock_event) = {
> > > >       .name                   = "riscv_timer_clockevent",
> > > > -     .features               = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_C3STOP,
> > > > +     .features               = CLOCK_EVT_FEAT_ONESHOT,
> > >
> > > A platform that depended on CLOCK_EVT_FEAT_C3STOP being set will break
> > > with this change because its existing DT will not have the new property.
> > >
> > > It needs to be the other way around which would effectively be the
> > > existing 'always-on' property.
> >
> > There are no RISC-V platforms using C3STOP. The patch which
> > added C3STOP has been reverted.
> > (Refer, https://lore.kernel.org/lkml/a218ebf8-0fba-168d-6598-c970bbff5faf@sholland.org/T/)
> >
> > I just need to rebase this patch upon the C3STOP revert patch.
>
> I guess you could say that the C3STOP addition was done spec-ulatively*,
> as the platform that actually exhibits that behaviour does not use the
> riscv-timer & its maintainer acked the revert (allwinner d1 family).
>
> *The spec does not make any guarantees about whether events arrive
> during suspend, only the behaviour *if* they arrive.
>
> Switching the property to "always-on" would require retrofitting that
> property to every other existing platform (and therefore regressing some
> behaviour there, no?).
>
> Most of the existing platforms are "toys" or demo platforms though, so
> it would not, I guess, be the end of the world to do so. Doubly so since
> none of them actually implement any sleep states that making it an
> "always-on" property.
>
> I've said since the start that defaulting to C3STOP is the "safer" thing
> to do, and although we disagreed on this last time Anup, I think the
> better outcome of someone missing a DT property is inaccessible sleep
> states rather than going into sleep states they cannot get out of.
>
> For PolarFire SoC, which I guess is one of the few "commerical"
> platforms, I'd be willing to accept retrofitting, since we have not yet
> implemented such sleep states yet.
>
> Maybe Prabhakar knows whether the RZ/Five has either a) implemented
> sleep states and b) which side of the "timer events arrive in suspend"
> divide their platform lies on.
> I'm particular interested here since that is not a SiFive core complex.
>
On RZ/Five we haven't implemented the sleep states yet.

Cheers,
Prabhakar