linux-kernel - Re: [PATCH 1/2] dt-bindings: watchdog: Add arm,smc-wdt watchdog arm,smc-wdt compatible

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Date:   Wed, 19 Feb 2020 16:30:46 -0600
From:   Rob Herring <robh@...nel.org>
To:     Evan Benn <evanbenn@...omium.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, jwerner@...omium.org,
        devicetree@...r.kernel.org, Guenter Roeck <linux@...ck-us.net>,
        "David S. Miller" <davem@...emloft.net>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-watchdog@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: watchdog: Add arm,smc-wdt watchdog
 arm,smc-wdt compatible

On Fri, Feb 14, 2020 at 05:26:36PM +1100, Evan Benn wrote:
> This watchdog can be used on ARM systems with a Secure
> Monitor firmware to forward watchdog operations to
> firmware via a Secure Monitor Call.
> 
> Signed-off-by: Evan Benn <evanbenn@...omium.org>
> ---
> 
>  .../bindings/watchdog/arm,smc-wdt.yaml        | 30 +++++++++++++++++++
>  MAINTAINERS                                   |  6 ++++
>  2 files changed, 36 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/watchdog/arm,smc-wdt.yaml
> 
> diff --git a/Documentation/devicetree/bindings/watchdog/arm,smc-wdt.yaml b/Documentation/devicetree/bindings/watchdog/arm,smc-wdt.yaml
> new file mode 100644
> index 000000000000..5170225b0c98
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/watchdog/arm,smc-wdt.yaml
> @@ -0,0 +1,30 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/watchdog/arm,smc-wdt.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: ARM Secure Monitor Call based watchdog

You are not the first 'watchdog in firmware accessed via an SMC call'. 
Is there some more detail about what implementation this is? Part of 
TF-A? Defined by some spec (I can dream)?

> +
> +allOf:
> +  - $ref: "watchdog.yaml#"
> +
> +maintainers:
> +  - Julius Werner <jwerner@...omium.org>
> +
> +properties:
> +  compatible:
> +    enum:
> +      - arm,smc-wdt
> +
> +required:
> +  - compatible
> +
> +examples:
> +  - |
> +    watchdog {

I'd expect this to be a child of whatever firmware implements this 
function.

> +      compatible = "arm,smc-wdt";
> +      timeout-sec = <15>;
> +    };
> +
> +...
> diff --git a/MAINTAINERS b/MAINTAINERS
> index e48ab79879ac..5c45536e1177 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1421,6 +1421,12 @@ S:	Maintained
>  F:	Documentation/devicetree/bindings/interrupt-controller/amazon,al-fic.txt
>  F:	drivers/irqchip/irq-al-fic.c
>  
> +ARM SMC WATCHDOG DRIVER
> +M:	Julius Werner <jwerner@...omium.org>
> +R:	Evan Benn <evanbenn@...omium.org>
> +S:	Maintained
> +F:	devicetree/bindings/watchdog/arm,smc-wdt.yaml
> +
>  ARM SMMU DRIVERS
>  M:	Will Deacon <will@...nel.org>
>  R:	Robin Murphy <robin.murphy@....com>
> -- 
> 2.25.0.265.gbab2e86ba0-goog
>