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

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Date:   Tue, 27 Jun 2017 14:44:18 -0500
From:   Christopher Bostic <cbostic@...ux.vnet.ibm.com>
To:     Joel Stanley <joel@....id.au>
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 6/26/17 9:59 PM, Joel Stanley wrote:
> 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.

I'll add the modes you describe.

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