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Date: Tue, 19 Oct 2021 13:31:44 +0200
From: Sebastian Reichel <sebastian.reichel@...labora.com>
To: David Heidelberg <david@...t.cz>
Cc: Rob Herring <robh+dt@...nel.org>, linux-pm@...r.kernel.org,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
~okias/devicetree@...ts.sr.ht
Subject: Re: [PATCH] dt-bindings: power: reset: gpio-poweroff: Convert txt
bindings to yaml
Hi,
On Sat, Oct 09, 2021 at 06:32:26PM +0200, David Heidelberg wrote:
> Convert power-off action connected to the GPIO documentation to the YAML syntax.
>
> Signed-off-by: David Heidelberg <david@...t.cz>
> ---
> .../bindings/power/reset/gpio-poweroff.txt | 41 ------------
> .../bindings/power/reset/gpio-poweroff.yaml | 64 +++++++++++++++++++
> 2 files changed, 64 insertions(+), 41 deletions(-)
> delete mode 100644 Documentation/devicetree/bindings/power/reset/gpio-poweroff.txt
> create mode 100644 Documentation/devicetree/bindings/power/reset/gpio-poweroff.yaml
>
> diff --git a/Documentation/devicetree/bindings/power/reset/gpio-poweroff.txt b/Documentation/devicetree/bindings/power/reset/gpio-poweroff.txt
> deleted file mode 100644
> index 3e56c1b34a4c..000000000000
> --- a/Documentation/devicetree/bindings/power/reset/gpio-poweroff.txt
> +++ /dev/null
> @@ -1,41 +0,0 @@
> -Driver a GPIO line that can be used to turn the power off.
> -
> -The driver supports both level triggered and edge triggered power off.
> -At driver load time, the driver will request the given gpio line and
> -install a handler to power off the system. If the optional properties
> -'input' is not found, the GPIO line will be driven in the inactive
> -state. Otherwise its configured as an input.
> -
> -When the power-off handler is called, the gpio is configured as an
> -output, and drive active, so triggering a level triggered power off
> -condition. This will also cause an inactive->active edge condition, so
> -triggering positive edge triggered power off. After a delay of 100ms,
> -the GPIO is set to inactive, thus causing an active->inactive edge,
> -triggering negative edge triggered power off. After another 100ms
> -delay the GPIO is driver active again. If the power is still on and
> -the CPU still running after a 3000ms delay, a WARN_ON(1) is emitted.
> -
> -Required properties:
> -- compatible : should be "gpio-poweroff".
> -- gpios : The GPIO to set high/low, see "gpios property" in
> - Documentation/devicetree/bindings/gpio/gpio.txt. If the pin should be
> - low to power down the board set it to "Active Low", otherwise set
> - gpio to "Active High".
> -
> -Optional properties:
> -- input : Initially configure the GPIO line as an input. Only reconfigure
> - it to an output when the power-off handler is called. If this optional
> - property is not specified, the GPIO is initialized as an output in its
> - inactive state.
> -- active-delay-ms: Delay (default 100) to wait after driving gpio active
> -- inactive-delay-ms: Delay (default 100) to wait after driving gpio inactive
> -- timeout-ms: Time to wait before asserting a WARN_ON(1). If nothing is
> - specified, 3000 ms is used.
> -
> -Examples:
> -
> -gpio-poweroff {
> - compatible = "gpio-poweroff";
> - gpios = <&gpio 4 0>;
> - timeout-ms = <3000>;
> -};
> diff --git a/Documentation/devicetree/bindings/power/reset/gpio-poweroff.yaml b/Documentation/devicetree/bindings/power/reset/gpio-poweroff.yaml
> new file mode 100644
> index 000000000000..50ae0cec6493
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/power/reset/gpio-poweroff.yaml
> @@ -0,0 +1,64 @@
> +# SPDX-License-Identifier: (GPL-2.0-only or BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/power/reset/gpio-poweroff.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Driver a GPIO line that can be used to turn the power off
This is a DT binding, not kernel driver documentation. Title should
be something like
title: GPIO controlled power off
> +
> +maintainers:
> + - Sebastian Reichel <sre@...nel.org>
> +
> +description:
> + The driver supports both level triggered and edge triggered power off.
> + At driver load time, the driver will request the given gpio line and
> + install a handler to power off the system. If the optional properties
> + 'input' is not found, the GPIO line will be driven in the inactive
> + state. Otherwise its configured as an input.
> +
> + When the power-off handler is called, the gpio is configured as an
> + output, and drive active, so triggering a level triggered power off
> + condition. This will also cause an inactive->active edge condition, so
> + triggering positive edge triggered power off. After a delay of 100ms,
> + the GPIO is set to inactive, thus causing an active->inactive edge,
> + triggering negative edge triggered power off. After another 100ms
> + delay the GPIO is driver active again. If the power is still on and
> + the CPU still running after a 3000ms delay, a WARN_ON(1) is emitted.
This description is quite Linux specific. I think it should be
easily possible to fix that:
System power off support via a GPIO line. When a shutdown is
executed the operating system is expected to switch the GPIO
from inactive to active. After a delay (active-delay-ms) it
is expected to be switched back to inactive. After another
delay (inactive-delay-ms) it is configured as active again.
Finally the operating system assumes the power off failed if
the system is still running after waiting some time (timeout-ms).
> +properties:
> + compatible:
> + const: gpio-poweroff
> +
> + gpios: true
maxItems: 1
> +
> + input:
> + description: |
> + Initially configure the GPIO line as an input. Only reconfigure
> + it to an output when the power-off handler is called. If this optional
type: boolean
s/handler is called/power off sequence is initiated/
> + property is not specified, the GPIO is initialized as an output in its inactive state.
> +
> + active-delay-ms:
> + default: 100
> + description: Delay to wait after driving gpio active
> +
> + inactive-delay-ms:
> + default: 100
> + description: Delay to wait after driving gpio inactive
> +
> + timeout-ms:
> + default: 3000
> + description: Time to wait before asserting a WARN_ON(1).
Time to wait before assuming the power off sequence failed.
> +required:
> + - compatible
> + - gpios
> +
> +additionalProperties: false
> +
> +examples:
> + - |
> + gpio-poweroff {
> + compatible = "gpio-poweroff";
> + gpios = <&gpio 4 0>;
> + timeout-ms = <3000>;
> + };
Thanks,
-- Sebastian
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