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

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Date:   Fri, 18 Aug 2023 12:16:25 -0700
From:   Elson Serrao <quic_eserrao@...cinc.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        <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 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

Hi Thinh,Roger
Please let me know your opinion on 'snps,skip-dwc3-halt-on-usb-suspend' 
as the quirk name.

Thanks
Elson