linux-kernel - Re: [PATCH 2/3] dt-bindings: watchdog: fsl-imx: document suspend in wait mode

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Message-ID: <d93503b7-fa65-d2ae-461f-56d68bf312e0@norik.com>
Date:   Thu, 20 Oct 2022 08:23:24 +0200
From:   Andrej Picej <andrej.picej@...ik.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Alexander Stein <alexander.stein@...tq-group.com>
Cc:     linux-watchdog@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, shawnguo@...nel.org,
        linux@...ck-us.net, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, linux-imx@....com, festevam@...il.com,
        kernel@...gutronix.de, s.hauer@...gutronix.de,
        wim@...ux-watchdog.org, robh+dt@...nel.org
Subject: Re: [PATCH 2/3] dt-bindings: watchdog: fsl-imx: document suspend in
 wait mode

Hi Alexander and Krzysztof,

hope I can reply to both questions here.

On 19. 10. 22 17:51, Krzysztof Kozlowski wrote:
> On 19/10/2022 09:00, Alexander Stein wrote:
>> Hello Andrej,
>>
>> Am Mittwoch, 19. Oktober 2022, 13:17:13 CEST schrieb Andrej Picej:
> 
> Missing commit msg.
> 
>>> Signed-off-by: Andrej Picej <andrej.picej@...ik.com>
>>> ---
>>>   Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.yaml | 5 +++++
>>>   1 file changed, 5 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.yaml
>>> b/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.yaml index
>>> fb7695515be1..01b3e04e7e65 100644
>>> --- a/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.yaml
>>> +++ b/Documentation/devicetree/bindings/watchdog/fsl-imx-wdt.yaml
>>> @@ -55,6 +55,11 @@ properties:
>>>         If present, the watchdog device is configured to assert its
>>>         external reset (WDOG_B) instead of issuing a software reset.
>>>
>>> +  fsl,suspend-in-wait:
>>> +    $ref: /schemas/types.yaml#/definitions/flag
>>> +    description: |
>>> +      If present, the watchdog device is suspended in WAIT mode.
>>> +
>>>   required:
>>>     - compatible
>>>     - interrupts
>>
>> What is the condition the watchdog is suspended in WAIT mode? Is this specific
>> to SoC or platform or something else?
>>
> 

Sorry, what exactly do you mean by condition? When the property 
"fsl,suspend-in-wait" is set the watchdog is suspended in WAIT mode, so 
this is defined by the user. Didn't want to apply it for all the 
supported machines since there could be devices which depend on watchdog 
triggering in WAIT mode. We stumbled on this problem on imx6 devices, 
but the same bit (with the same description) is found on imx25, imx35, 
imx50/51/53, imx7 and imx8.

> And what happens else? When it is not suspended in WAIT mode?
> 

When you put the device in "freeze"/"Suspend-To-Idle" low-power mode the 
watchdog keeps running and triggers a reset after 128 seconds. So the 
maximum length the device can stay in this mode is limited to 128 seconds.

Hope this answers your questions.

Best regards,
Andrej