linux-kernel - Re: [PATCH v4 2/3] dt-bindings: usb: snps,dwc3: Add runtime-suspend-on-usb-suspend property

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Message-ID: <31fa930a-51fb-6a7f-300d-e71f6b399eb1@linaro.org>
Date:   Sat, 19 Aug 2023 11:35:34 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Elson Serrao <quic_eserrao@...cinc.com>,
        gregkh@...uxfoundation.org, Thinh.Nguyen@...opsys.com,
        rogerq@...nel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        devicetree@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org
Subject: Re: [PATCH v4 2/3] dt-bindings: usb: snps,dwc3: Add
 runtime-suspend-on-usb-suspend property

On 18/08/2023 21:16, Elson Serrao wrote:
> 
> 
> On 8/15/2023 10:44 PM, Krzysztof Kozlowski wrote:
>> On 14/08/2023 20:50, Elson Roy Serrao wrote:
>>> This property allows dwc3 runtime suspend when bus suspend interrupt
>>> is received even with cable connected. This would allow the dwc3
>>> controller to enter low power mode during bus suspend scenario.
>>>
>>> This property would particularly benefit dwc3 IPs where hibernation is
>>> not enabled and the dwc3 low power mode entry/exit is handled by the
>>> glue driver. The assumption here is that the platform using this dt
>>> property is capable of detecting resume events to bring the controller
>>> out of suspend.
>>>
>>> Signed-off-by: Elson Roy Serrao <quic_eserrao@...cinc.com>
>>> ---
>>>   Documentation/devicetree/bindings/usb/snps,dwc3.yaml | 5 +++++
>>>   1 file changed, 5 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/usb/snps,dwc3.yaml b/Documentation/devicetree/bindings/usb/snps,dwc3.yaml
>>> index a696f23730d3..e19a60d06d2b 100644
>>> --- a/Documentation/devicetree/bindings/usb/snps,dwc3.yaml
>>> +++ b/Documentation/devicetree/bindings/usb/snps,dwc3.yaml
>>> @@ -403,6 +403,11 @@ properties:
>>>       description:
>>>         Enable USB remote wakeup.
>>>   
>>> +  snps,runtime-suspend-on-usb-suspend:
>>> +    description:
>>> +      If True then dwc3 runtime suspend is allowed during bus suspend
>>> +      case even with the USB cable connected.
>>
>> This was no tested... but anyway, this is no a DT property but OS
>> policy. There is no such thing as "runtime suspend" in the hardware,
>> because you describe one particular OS.
>>
>> Sorry, no a DT property, drop the change entirely.
>>
>>
> Hi Krzysztof
> 
> Sorry my local dt checker had some issue and it did not catch these 
> errors. I have rectified it now.
> 
> This dt property is mainly for skipping dwc3 controller halt when a USB 
> suspend interrupt is received with usb cable connected, so that we dont 
> trigger a DISCONNECT event. Perhaps a better name would reflect the true 
> usage of this?
> 
> Something like snps,skip-dwc3-halt-on-usb-suspend. dwc3 cores where 
> hibernation feature is not enabled/supported can use this property

So this is specific to DWC3 core, thus should be just implied by compatible.

Best regards,
Krzysztof