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

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Message-Id: <6f2a77e0-e64c-70b7-812a-6a5e8a0b5e6f@linux.vnet.ibm.com>
Date:   Tue, 27 Jun 2017 16:42:24 -0500
From:   Christopher Bostic <cbostic@...ux.vnet.ibm.com>
To:     Guenter Roeck <linux@...ck-us.net>
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 6/27/17 4:32 PM, Guenter Roeck wrote:
> 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.

No these aren't bitmasks.   The example was intended to indicate what 
could be used.
In practice only a subset of each of these properties would make any 
sense.   How
would you suggest the example be formatted to convey that? Multiple examples
I suppose.

Thanks,
Chris

> Guenter
>