linux-kernel - Re: [PATCH v3 2/3] Documentation: DT: binding documentation for regulator-poweroff

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Date:   Tue, 8 Dec 2020 11:13:58 +0100
From:   Maxime Ripard <maxime@...no.tech>
To:     Michael Klein <michael@...sekall.de>
Cc:     Sebastian Reichel <sre@...nel.org>,
        Rob Herring <robh+dt@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 2/3] Documentation: DT: binding documentation for
 regulator-poweroff

On Mon, Dec 07, 2020 at 03:27:55PM +0100, Michael Klein wrote:
> Add devicetree binding documentation for regulator-poweroff driver.
> 
> Signed-off-by: Michael Klein <michael@...sekall.de>
> ---
>  .../power/reset/regulator-poweroff.yaml       | 53 +++++++++++++++++++
>  1 file changed, 53 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/power/reset/regulator-poweroff.yaml
> 
> diff --git a/Documentation/devicetree/bindings/power/reset/regulator-poweroff.yaml b/Documentation/devicetree/bindings/power/reset/regulator-poweroff.yaml
> new file mode 100644
> index 000000000000..8c8ce6bb031a
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/power/reset/regulator-poweroff.yaml
> @@ -0,0 +1,53 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/power/reset/regulator-poweroff.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Force-disable power regulators to turn the power off.
> +
> +maintainers:
> +  - Michael Klein <michael@...sekall.de>
> +
> +description: |
> +  When the power-off handler is called, one more regulators are disabled
> +  by calling regulator_force_disable(). If the power is still on and the
> +  CPU still running after a 3000ms delay, a WARN_ON(1) is emitted.
> +
> +properties:
> +  compatible:
> +    const: "regulator-poweroff"
> +
> +  regulator-names:
> +    description:
> +      Array of regulator names
> +    $ref: /schemas/types.yaml#/definitions/string-array
> +
> +  REGULATOR-supply:

This should be a patternProperties

> +    description:
> +      For any REGULATOR listed in regulator-names, a phandle
> +      to the corresponding regulator node
> +    $ref: /schemas/types.yaml#/definitions/phandle
> +
> +  timeout-ms:
> +    description:
> +      Time to wait before asserting a WARN_ON(1). If nothing is
> +      specified, 3000 ms is used.
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +
> +required:
> +  - compatible
> +  - regulator-names
> +  - REGULATOR-supply
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    regulator-poweroff {
> +        compatible = "regulator-poweroff";
> +        regulator-names = "vcc1v2", "vcc-dram";
> +        vcc1v2-supply = <&reg_vcc1v2>;
> +        vcc-dram-supply = <&reg_vcc_dram>;
> +    };

I'm not entirely sure how multiple regulators would work here. I guess
the ordering is board/purpose sensitive. In this particular case, I
assume that vcc1v2 would be shut down before vcc-dram?

If so, I would expect that one regulator_force_disable is run, the CPU
is disabled and you never get the chance to cut vcc-dram.

Similarly, cutting the RAM regulator first would probably be fine if
you're running code from the cache / SRAM, but I don't see anything
making sure it's the case in the driver?

Maxime

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