linux-kernel - Re: [PATCH 1/2] drivers/watchdog: Document new aspeed optional dev tree properties.

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Message-ID: <CACPK8Xe4kWoZKhwRWD+p-zFz-EQDn_3Q5=U4tUX-n6paKMYy1A@mail.gmail.com>
Date:   Tue, 27 Jun 2017 12:29:41 +0930
From:   Joel Stanley <joel@....id.au>
To:     Christopher Bostic <cbostic@...ux.vnet.ibm.com>
Cc:     Wim Van Sebroeck <wim@...ana.be>,
        Guenter Roeck <linux@...ck-us.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-watchdog@...r.kernel.org, Andrew Jeffery <andrew@...id.au>
Subject: Re: [PATCH 1/2] drivers/watchdog: Document new aspeed optional dev
 tree properties.

On Wed, Jun 14, 2017 at 6:08 AM, Christopher Bostic
<cbostic@...ux.vnet.ibm.com> wrote:
> Describe new optional property 'external-signal'.  When present in the
> system device tree an exernal signal is generated on watchdog timeout.
>
> Describe new optional property 'no-system-reset'.  When present in the
> system device tree no system reset is to occur on watchdog timeout.
> System reset in this case is managed by one of the other watchogs
> available.
>
> Signed-off-by: Christopher Bostic <cbostic@...ux.vnet.ibm.com>
> ---
>  Documentation/devicetree/bindings/watchdog/aspeed-wdt.txt | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/watchdog/aspeed-wdt.txt b/Documentation/devicetree/bindings/watchdog/aspeed-wdt.txt
> index c5e74d7..4099ea5 100644
> --- a/Documentation/devicetree/bindings/watchdog/aspeed-wdt.txt
> +++ b/Documentation/devicetree/bindings/watchdog/aspeed-wdt.txt
> @@ -8,9 +8,20 @@ Required properties:
>   - reg: physical base address of the controller and length of memory mapped
>     region
>
> +Optional properties:
> + - external-signal: If the property is present then an external signal is to
> +   be generated on watchdog timeout.  If absent, external signal is not
> +   generated.
> +
> + - no-system-reset: If the property is present then system will not be reset
> +   on watchdog timeout. In this case one of the other watchdogs will handle
> +   reset.  If absent then the watchdog resets the system on timeout.

I'm not sure that this describes the hardware. The datasheet says:

Whenever timeout ocurs, WDT can program to generate 6 types of signals:

 * ARM reset signal: to reset ARM CPU only
 * SOC reset signal: to reset SOC part function
 * System reset signal: to reset full chip
 * Interrupt signal: to interrupt CPU
 * Eternal signal: to external reset counter (only WDT1 and WDT2)
 * Alternate boot signal: to boot from alternate block

I think your bindings should describe these modes where possible.

Cheers,

Joel


> +
>  Example:
>
>         wdt1: watchdog@...85000 {
>                 compatible = "aspeed,ast2400-wdt";
>                 reg = <0x1e785000 0x1c>;
> +               external-signal;
> +               no-system-reset;
>         };
> --
> 1.8.2.2
>