[PATCH v4 0/5] regulator: add under-voltage support (part 2)

[PATCH v4 0/5] regulator: add under-voltage support (part 2)

[Oleksij Rempel]

This series add under-voltage and emergency shutdown for system critical
regulators

changes v4:
- rebase against latest regulator/for-next
- drop mainlined patches
- rename regulator-uv-survival-time-ms to regulator-uv-less-critical-window-ms
  to fit it to actual use case
- avoid some of words in commit messages
- us switch case to parse critical events

changes v3:
- add system-critical-regulator property
- add regulator-uv-survival-time-ms property
- implement default policy for system critical uv events

changes v2:
- drop event forwarding support
- use emergency shutdown directly instead of generating under-voltage
  error event.
- fix devicetree patch
- drop interrupt-names support

Oleksij Rempel (5):
  regulator: dt-bindings: Add system-critical-regulator property
  regulator: Introduce handling for system-critical under-voltage events
  regulator: dt-bindings: Allow system-critical marking for
    fixed-regulator
  regulator: dt-bindings: Add 'regulator-uv-less-critical-window-ms'
    property
  regulator: Implement uv_survival_time for handling under-voltage
    events

 .../bindings/regulator/fixed-regulator.yaml   |  2 +
 .../bindings/regulator/regulator.yaml         | 13 +++++++
 drivers/regulator/core.c                      | 38 +++++++++++++++++++
 drivers/regulator/of_regulator.c              |  9 +++++
 include/linux/regulator/machine.h             | 18 +++++++++
 5 files changed, 80 insertions(+)

-- 
2.39.2

[PATCH v4 1/5] regulator: dt-bindings: Add system-critical-regulator property

[Oleksij Rempel]

Introduce a new Device Tree property 'system-critical-regulator' for
marking a regulator as crucial for system stability or functionality.
This helps in distinguishing regulators that are vital for system
operations and may require special handling in under-voltage scenarios.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
 Documentation/devicetree/bindings/regulator/regulator.yaml | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Documentation/devicetree/bindings/regulator/regulator.yaml b/Documentation/devicetree/bindings/regulator/regulator.yaml
index 9daf0fc2465f..5b8d55f7c43b 100644
--- a/Documentation/devicetree/bindings/regulator/regulator.yaml
+++ b/Documentation/devicetree/bindings/regulator/regulator.yaml
@@ -114,6 +114,11 @@ properties:
     description: Enable pull down resistor when the regulator is disabled.
     type: boolean
 
+  system-critical-regulator:
+    description: Set if the regulator is critical to system stability or
+      functionality.
+    type: boolean
+
   regulator-over-current-protection:
     description: Enable over current protection.
     type: boolean
-- 
2.39.2

Re: [PATCH v4 1/5] regulator: dt-bindings: Add system-critical-regulator property

[Rob Herring]

On Thu, 26 Oct 2023 16:48:20 +0200, Oleksij Rempel wrote:
> Introduce a new Device Tree property 'system-critical-regulator' for
> marking a regulator as crucial for system stability or functionality.
> This helps in distinguishing regulators that are vital for system
> operations and may require special handling in under-voltage scenarios.
> 
> Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
> ---
>  Documentation/devicetree/bindings/regulator/regulator.yaml | 5 +++++
>  1 file changed, 5 insertions(+)
> 

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

[PATCH v4 2/5] regulator: Introduce handling for system-critical under-voltage events

[Oleksij Rempel]

Handle under-voltage events for crucial regulators to maintain system
stability and avoid issues during power drops.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
 drivers/regulator/core.c          | 38 +++++++++++++++++++++++++++++++
 drivers/regulator/of_regulator.c  |  2 ++
 include/linux/regulator/machine.h | 10 ++++++++
 3 files changed, 50 insertions(+)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 3137e40fcd3e..a072f721f288 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -19,6 +19,7 @@
 #include <linux/delay.h>
 #include <linux/gpio/consumer.h>
 #include <linux/of.h>
+#include <linux/reboot.h>
 #include <linux/regmap.h>
 #include <linux/regulator/of_regulator.h>
 #include <linux/regulator/consumer.h>
@@ -5061,6 +5062,41 @@ void regulator_bulk_free(int num_consumers,
 }
 EXPORT_SYMBOL_GPL(regulator_bulk_free);
 
+/**
+ * regulator_handle_critical - Handle events for system-critical regulators.
+ * @rdev: The regulator device.
+ * @event: The event being handled.
+ *
+ * This function handles critical events such as under-voltage, over-current,
+ * and unknown errors for regulators deemed system-critical. On detecting such
+ * events, it triggers a hardware protection shutdown with a defined timeout.
+ */
+static void regulator_handle_critical(struct regulator_dev *rdev,
+				      unsigned long event)
+{
+	const char *reason = NULL;
+
+	if (!rdev->constraints->system_critical)
+		return;
+
+	switch (event) {
+	case REGULATOR_EVENT_UNDER_VOLTAGE:
+		reason = "System critical regulator: voltage drop detected";
+		break;
+	case REGULATOR_EVENT_OVER_CURRENT:
+		reason = "System critical regulator: over-current detected";
+		break;
+	case REGULATOR_EVENT_FAIL:
+		reason = "System critical regulator: unknown error";
+	}
+
+	if (!reason)
+		return;
+
+	hw_protection_shutdown(reason,
+			       REGULATOR_DEF_UV_LESS_CRITICAL_WINDOW_MS);
+}
+
 /**
  * regulator_notifier_call_chain - call regulator event notifier
  * @rdev: regulator source
@@ -5073,6 +5109,8 @@ EXPORT_SYMBOL_GPL(regulator_bulk_free);
 int regulator_notifier_call_chain(struct regulator_dev *rdev,
 				  unsigned long event, void *data)
 {
+	regulator_handle_critical(rdev, event);
+
 	_notifier_call_chain(rdev, event, data);
 	return NOTIFY_DONE;
 
diff --git a/drivers/regulator/of_regulator.c b/drivers/regulator/of_regulator.c
index 1b65e5e4e40f..3bdd6f1919a4 100644
--- a/drivers/regulator/of_regulator.c
+++ b/drivers/regulator/of_regulator.c
@@ -131,6 +131,8 @@ static int of_get_regulation_constraints(struct device *dev,
 		constraints->valid_ops_mask |= REGULATOR_CHANGE_STATUS;
 
 	constraints->pull_down = of_property_read_bool(np, "regulator-pull-down");
+	constraints->system_critical = of_property_read_bool(np,
+						"system-critical-regulator");
 
 	if (of_property_read_bool(np, "regulator-allow-bypass"))
 		constraints->valid_ops_mask |= REGULATOR_CHANGE_BYPASS;
diff --git a/include/linux/regulator/machine.h b/include/linux/regulator/machine.h
index 621b7f4a3639..e0ddfb5593c9 100644
--- a/include/linux/regulator/machine.h
+++ b/include/linux/regulator/machine.h
@@ -49,6 +49,13 @@ struct regulator;
 #define DISABLE_IN_SUSPEND	1
 #define ENABLE_IN_SUSPEND	2
 
+/*
+ * Default time window (in milliseconds) following a critical under-voltage
+ * event during which less critical actions can be safely carried out by the
+ * system.
+ */
+#define REGULATOR_DEF_UV_LESS_CRITICAL_WINDOW_MS	10
+
 /* Regulator active discharge flags */
 enum regulator_active_discharge {
 	REGULATOR_ACTIVE_DISCHARGE_DEFAULT,
@@ -127,6 +134,8 @@ struct notification_limit {
  * @ramp_disable: Disable ramp delay when initialising or when setting voltage.
  * @soft_start: Enable soft start so that voltage ramps slowly.
  * @pull_down: Enable pull down when regulator is disabled.
+ * @system_critical: Set if the regulator is critical to system stability or
+ *                   functionality.
  * @over_current_protection: Auto disable on over current event.
  *
  * @over_current_detection: Configure over current limits.
@@ -214,6 +223,7 @@ struct regulation_constraints {
 	unsigned ramp_disable:1; /* disable ramp delay */
 	unsigned soft_start:1;	/* ramp voltage slowly */
 	unsigned pull_down:1;	/* pull down resistor when regulator off */
+	unsigned system_critical:1;	/* critical to system stability */
 	unsigned over_current_protection:1; /* auto disable on over current */
 	unsigned over_current_detection:1; /* notify on over current */
 	unsigned over_voltage_detection:1; /* notify on over voltage */
-- 
2.39.2

[PATCH v4 3/5] regulator: dt-bindings: Allow system-critical marking for fixed-regulator

[Oleksij Rempel]

In certain projects, the main system regulator, composed of simple
components including an under-voltage detector and capacitors, can be
aptly described as a fixed regulator in the device tree. To cater to
such use cases, this patch extends the fixed regulator binding to
support the 'system-critical-regulator' property. This property
signifies that the fixed-regulator is vital for system stability.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
 .../devicetree/bindings/regulator/fixed-regulator.yaml          | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Documentation/devicetree/bindings/regulator/fixed-regulator.yaml b/Documentation/devicetree/bindings/regulator/fixed-regulator.yaml
index ce7751b9129c..9ff9abf2691a 100644
--- a/Documentation/devicetree/bindings/regulator/fixed-regulator.yaml
+++ b/Documentation/devicetree/bindings/regulator/fixed-regulator.yaml
@@ -105,6 +105,8 @@ properties:
     description:
       Interrupt signaling a critical under-voltage event.
 
+  system-critical-regulator: true
+
 required:
   - compatible
   - regulator-name
-- 
2.39.2

Re: [PATCH v4 3/5] regulator: dt-bindings: Allow system-critical marking for fixed-regulator

[Rob Herring]

On Thu, Oct 26, 2023 at 04:48:22PM +0200, Oleksij Rempel wrote:
> In certain projects, the main system regulator, composed of simple
> components including an under-voltage detector and capacitors, can be
> aptly described as a fixed regulator in the device tree. To cater to
> such use cases, this patch extends the fixed regulator binding to
> support the 'system-critical-regulator' property. This property
> signifies that the fixed-regulator is vital for system stability.

There is no programming interface for fixed-regulators, so how do you 
know an under/over voltage condition?

> 
> Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
> ---
>  .../devicetree/bindings/regulator/fixed-regulator.yaml          | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/regulator/fixed-regulator.yaml b/Documentation/devicetree/bindings/regulator/fixed-regulator.yaml
> index ce7751b9129c..9ff9abf2691a 100644
> --- a/Documentation/devicetree/bindings/regulator/fixed-regulator.yaml
> +++ b/Documentation/devicetree/bindings/regulator/fixed-regulator.yaml
> @@ -105,6 +105,8 @@ properties:
>      description:
>        Interrupt signaling a critical under-voltage event.
>  
> +  system-critical-regulator: true
> +
>  required:
>    - compatible
>    - regulator-name
> -- 
> 2.39.2
> 

Re: [PATCH v4 3/5] regulator: dt-bindings: Allow system-critical marking for fixed-regulator

[Mark Brown]

[-- Attachment #1: Type: text/plain, Size: 833 bytes --]

On Fri, Oct 27, 2023 at 04:24:40PM -0500, Rob Herring wrote:
> On Thu, Oct 26, 2023 at 04:48:22PM +0200, Oleksij Rempel wrote:

> > In certain projects, the main system regulator, composed of simple
> > components including an under-voltage detector and capacitors, can be
> > aptly described as a fixed regulator in the device tree. To cater to
> > such use cases, this patch extends the fixed regulator binding to
> > support the 'system-critical-regulator' property. This property
> > signifies that the fixed-regulator is vital for system stability.

> There is no programming interface for fixed-regulators, so how do you 
> know an under/over voltage condition?

There's support for interrupts now - it's a just a simple signal so if
the interrupt is asserted you know there's an error but that's all you
know.

[-- Attachment #2: signature.asc --]
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Re: [PATCH v4 3/5] regulator: dt-bindings: Allow system-critical marking for fixed-regulator

[Rob Herring]

On Thu, 26 Oct 2023 16:48:22 +0200, Oleksij Rempel wrote:
> In certain projects, the main system regulator, composed of simple
> components including an under-voltage detector and capacitors, can be
> aptly described as a fixed regulator in the device tree. To cater to
> such use cases, this patch extends the fixed regulator binding to
> support the 'system-critical-regulator' property. This property
> signifies that the fixed-regulator is vital for system stability.
> 
> Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
> ---
>  .../devicetree/bindings/regulator/fixed-regulator.yaml          | 2 ++
>  1 file changed, 2 insertions(+)
> 

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

[PATCH v4 4/5] regulator: dt-bindings: Add 'regulator-uv-less-critical-window-ms' property

[Oleksij Rempel]

Introduces a new devicetree property to specifies the time window (in
milliseconds) following a critical under-voltage (UV) event during which
less critical actions can be safely carried out by the system.

Less Critical Actions:
- Logging the under-voltage event for later analysis.
- Saving less critical data that may be useful for diagnosing issues or
  for audit purposes.

More Critical Actions (post the less critical window):
- Initiating procedures to properly shutdown hardware to prevent damage.

The 'regulator-uv-less-critical-window-ms' property is crucial for
conveying board-specific hardware characteristics, not for enforcing a
certain policy. The time window represented by this property is derived
from the physical attributes of the hardware like the capacity of
on-board capacitors, the power consumption of the components, and the
time needed to safely shut down hardware to prevent damage. These
attributes can significantly vary between different boards, making it a
board-specific property rather than a policy directive.

By providing a precise representation of the time available for less
critical actions post an under-voltage event, this property enables the
kernel to make informed decisions on action prioritization, ensuring
that essential preventative measures are taken to avoid hardware damage
while also allowing for data capture and analysis.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
 .../devicetree/bindings/regulator/regulator.yaml          | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/Documentation/devicetree/bindings/regulator/regulator.yaml b/Documentation/devicetree/bindings/regulator/regulator.yaml
index 5b8d55f7c43b..1ef380d1515e 100644
--- a/Documentation/devicetree/bindings/regulator/regulator.yaml
+++ b/Documentation/devicetree/bindings/regulator/regulator.yaml
@@ -186,6 +186,14 @@ properties:
       be enabled but limit setting can be omitted. Limit is given as microvolt
       offset from voltage set to regulator.
 
+  regulator-uv-less-critical-window-ms:
+    description: Specifies the time window (in milliseconds) following a
+      critical under-voltage event during which the system can continue to
+      operate safely while performing less critical operations. This property
+      provides a defined duration before a more severe reaction to the
+      under-voltage event is needed, allowing for certain non-urgent actions to
+      be carried out in preparation for potential power loss.
+
   regulator-temp-protection-kelvin:
     description: Set over temperature protection limit. This is a limit where
       hardware performs emergency shutdown. Zero can be passed to disable
-- 
2.39.2

Re: [PATCH v4 4/5] regulator: dt-bindings: Add 'regulator-uv-less-critical-window-ms' property

[Rob Herring]

On Thu, 26 Oct 2023 16:48:23 +0200, Oleksij Rempel wrote:
> Introduces a new devicetree property to specifies the time window (in
> milliseconds) following a critical under-voltage (UV) event during which
> less critical actions can be safely carried out by the system.
> 
> Less Critical Actions:
> - Logging the under-voltage event for later analysis.
> - Saving less critical data that may be useful for diagnosing issues or
>   for audit purposes.
> 
> More Critical Actions (post the less critical window):
> - Initiating procedures to properly shutdown hardware to prevent damage.
> 
> The 'regulator-uv-less-critical-window-ms' property is crucial for
> conveying board-specific hardware characteristics, not for enforcing a
> certain policy. The time window represented by this property is derived
> from the physical attributes of the hardware like the capacity of
> on-board capacitors, the power consumption of the components, and the
> time needed to safely shut down hardware to prevent damage. These
> attributes can significantly vary between different boards, making it a
> board-specific property rather than a policy directive.
> 
> By providing a precise representation of the time available for less
> critical actions post an under-voltage event, this property enables the
> kernel to make informed decisions on action prioritization, ensuring
> that essential preventative measures are taken to avoid hardware damage
> while also allowing for data capture and analysis.
> 
> Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
> ---
>  .../devicetree/bindings/regulator/regulator.yaml          | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 

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

[PATCH v4 5/5] regulator: Implement uv_survival_time for handling under-voltage events

[Oleksij Rempel]

Add 'uv_survival_time' field to regulation_constraints for specifying
survival time post critical under-voltage event. Update the regulator
notifier call chain and Device Tree property parsing to use this new
field, allowing a configurable timeout before emergency shutdown.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
 drivers/regulator/core.c          | 2 +-
 drivers/regulator/of_regulator.c  | 7 +++++++
 include/linux/regulator/machine.h | 8 ++++++++
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index a072f721f288..a6cb84af989e 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -5094,7 +5094,7 @@ static void regulator_handle_critical(struct regulator_dev *rdev,
 		return;
 
 	hw_protection_shutdown(reason,
-			       REGULATOR_DEF_UV_LESS_CRITICAL_WINDOW_MS);
+			       rdev->constraints->uv_less_critical_window_ms);
 }
 
 /**
diff --git a/drivers/regulator/of_regulator.c b/drivers/regulator/of_regulator.c
index 3bdd6f1919a4..03afc160fc72 100644
--- a/drivers/regulator/of_regulator.c
+++ b/drivers/regulator/of_regulator.c
@@ -175,6 +175,13 @@ static int of_get_regulation_constraints(struct device *dev,
 	if (!ret)
 		constraints->enable_time = pval;
 
+	ret = of_property_read_u32(np, "regulator-uv-survival-time-ms", &pval);
+	if (!ret)
+		constraints->uv_less_critical_window_ms = pval;
+	else
+		constraints->uv_less_critical_window_ms =
+				REGULATOR_DEF_UV_LESS_CRITICAL_WINDOW_MS;
+
 	constraints->soft_start = of_property_read_bool(np,
 					"regulator-soft-start");
 	ret = of_property_read_u32(np, "regulator-active-discharge", &pval);
diff --git a/include/linux/regulator/machine.h b/include/linux/regulator/machine.h
index e0ddfb5593c9..0cd76d264727 100644
--- a/include/linux/regulator/machine.h
+++ b/include/linux/regulator/machine.h
@@ -162,6 +162,13 @@ struct notification_limit {
  *		      regulator_active_discharge values are used for
  *		      initialisation.
  * @enable_time: Turn-on time of the rails (unit: microseconds)
+ * @uv_less_critical_window_ms: Specifies the time window (in milliseconds)
+ *                              following a critical under-voltage (UV) event
+ *                              during which less critical actions can be
+ *                              safely carried out by the system (for example
+ *                              logging). After this time window more critical
+ *                              actions should be done (for example prevent
+ *                              HW damage).
  */
 struct regulation_constraints {
 
@@ -213,6 +220,7 @@ struct regulation_constraints {
 	unsigned int settling_time_up;
 	unsigned int settling_time_down;
 	unsigned int enable_time;
+	unsigned int uv_less_critical_window_ms;
 
 	unsigned int active_discharge;
 
-- 
2.39.2

Re: [PATCH v4 0/5] regulator: add under-voltage support (part 2)

[Mark Brown]

On Thu, 26 Oct 2023 16:48:19 +0200, Oleksij Rempel wrote:
> This series add under-voltage and emergency shutdown for system critical
> regulators
> 
> changes v4:
> - rebase against latest regulator/for-next
> - drop mainlined patches
> - rename regulator-uv-survival-time-ms to regulator-uv-less-critical-window-ms
>   to fit it to actual use case
> - avoid some of words in commit messages
> - us switch case to parse critical events
> 
> [...]

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/regulator.git for-next

Thanks!

[1/5] regulator: dt-bindings: Add system-critical-regulator property
      commit: 0e1c8dcbdecefea93dee19419b2f67dca591dd42
[2/5] regulator: Introduce handling for system-critical under-voltage events
      commit: 8156c7dd47b92fc4a70c9ea58e7a9e88c8bc32be
[3/5] regulator: dt-bindings: Allow system-critical marking for fixed-regulator
      commit: 633cd1c0a9de7609f97c0c86e3ac81153e8263b0
[4/5] regulator: dt-bindings: Add 'regulator-uv-less-critical-window-ms' property
      commit: 759e2bd96971763db1cfaf6cafc07654b12aa21e
[5/5] regulator: Implement uv_survival_time for handling under-voltage events
      commit: 1e22152aa59d793743fc53051dd7a042f362aecb

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark