linux-kernel - Re: [PATCH v2 1/2] drivers/watchdog: Add optional ASPEED device tree properties

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Date:   Tue, 27 Jun 2017 14:32:16 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Christopher Bostic <cbostic@...ux.vnet.ibm.com>
Cc:     wim@...ana.be, robh+dt@...nel.org, mark.rutland@....com,
        joel@....id.au, linux-watchdog@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] drivers/watchdog: Add optional ASPEED device tree
 properties

On Tue, Jun 27, 2017 at 04:17:33PM -0500, Christopher Bostic wrote:
> Describe device tree optional properties:
> 
>   * aspeed,arm-reet - ARM CPU reset on signal
>   * aspeed,soc-reset - SOC reset on signal
>   * aspeed,sys-reset - System reset on signal
>           Disabling system reset may be required in situations where
>           one of the other watchdog engines in the system is responsible
>           for this.
>   * aspeed,interrupt - Interrupt CPU on signal
>   * aspeed,external-signal - Generate external signal (WDT1 and WDT2 only)
>   * aspeed,alt-boot - Boot from alternate block on signal
> 
> Signed-off-by: Christopher Bostic <cbostic@...ux.vnet.ibm.com>
> ---
> v2 - Add 'aspeed,' prefix to all optional properties
>    - Add arm-reset, soc-reset, interrupt, alt-boot properties
> ---
>  .../devicetree/bindings/watchdog/aspeed-wdt.txt    | 25 ++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/watchdog/aspeed-wdt.txt b/Documentation/devicetree/bindings/watchdog/aspeed-wdt.txt
> index c5e74d7..555b8b4 100644
> --- a/Documentation/devicetree/bindings/watchdog/aspeed-wdt.txt
> +++ b/Documentation/devicetree/bindings/watchdog/aspeed-wdt.txt
> @@ -8,9 +8,34 @@ Required properties:
>   - reg: physical base address of the controller and length of memory mapped
>     region
>  
> +Optional properties:
> +   Signal behavior - Whenever a timeout occurs, the watchdog can be programmed
> +   to generate 6 types of signals:
> +
> + - aspeed,arm-reset:  If property is present then reset ARM CPU only.
> +
> + - aspeed,soc-reset:  If property is present then reset SOC.
> +
> + - aspeed,sys-reset:  If property is present then reset the entire chip.
> +                      In cases where one of the other watchdog engines
> +                      in the system is responsible for system reset it
> +                      may be required to not specify this property.
> +
> + - aspeed,interrupt:  If property is present then interrupt CPU.
> +
> + - aspeed,external-signal: If property is present then signal is sent to
> +                           external reset counter (only WDT1 and WDT2).
> + - aspeed,alt-boot:    If property is present then boot from alternate block.
> +
>  Example:
>  
>  	wdt1: watchdog@...85000 {
>  		compatible = "aspeed,ast2400-wdt";
>  		reg = <0x1e785000 0x1c>;
> +		aspeed,arm-reset;
> +		aspeed,soc-reset;
> +		aspeed,sys-reset;
> +		aspeed,interrupt;
> +		aspeed,external-signal;
> +		aspeed,alt-boot;

Is that a bit mask or a value ? I would have thought that,
for example, a complete system reset would include the SoC reset,
and a SoC reset would include the ARM reset. Generating an
interrupt while at the same time resetting the system (or
part of it) doesn't seem to make much sense either.

Guenter