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: <63c9ced1-6204-88e9-1dae-2979388bbc67@quicinc.com>
Date:   Thu, 21 Sep 2023 10:09:21 -0700
From:   Elson Serrao <quic_eserrao@...cinc.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>
CC:     Roger Quadros <rogerq@...nel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "conor+dt@...nel.org" <conor+dt@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        <quic_kriskura@...cinc.com>
Subject: Re: [PATCH v4 2/3] dt-bindings: usb: snps,dwc3: Add
 runtime-suspend-on-usb-suspend property



On 8/30/2023 11:29 PM, Krzysztof Kozlowski wrote:
> On 31/08/2023 05:01, Thinh Nguyen wrote:
>> On Wed, Aug 30, 2023, Krzysztof Kozlowski wrote:
>>> On 30/08/2023 06:31, Elson Serrao wrote:
>>>>
>>>>
>>>> On 8/29/2023 6:37 PM, Thinh Nguyen wrote:
>>>>> Just want to clarify, there are dwc3 properties and there are dt binding
>>>>> properties. Often the case that dt binding matches 1-to-1 with dwc3
>>>>> driver property. Now, we need to enhance the checkers so that the dwc3
>>>>> driver property to match cases where it is platform specific and through
>>>>> compatible string.
>>>>>
>>>>
>>>> Thank you for the clarification Thinh.
>>>> To confirm, we would need to modify the driver to parse a new compatible
>>>> string (say "snps,dwc3-ext-wakeup") and add .data field so that the
>>>> driver is aware that this particular platform supports external wakeup
>>>> detection.Right ?
>>>
>>> No, it's not then platform specific. You said it depends on each
>>> platform. Platform is Qualcomm SM8450 for example.
>>>
>>
>> Hi Elson,
>>
>> Use the compatible string of your platform.
>>
>> e.g.
>> if (dev->of_node) {
>> 	struct device_node *parent = of_get_parent(dev->of_node);
>>
>> 	dwc->no_disconnect_on_usb_suspend =
>> 		of_device_is_compatible(parent, "qcom,your-compatible-string") ||
>> 		of_device_is_compatible(parent, "some-other-platform");
>> }
>>
>> You need to enhance dwc3_get_properties(). This may get big as dwc3 adds
>> more properties. Perhaps you can help come up with ideas to keep this
>> clean. Perhaps we can separate this out of dwc3 core.c?

HI Thinh

Apologies for the delayed response.
Series 
https://patchwork.kernel.org/project/linux-usb/cover/1655094654-24052-1-git-send-email-quic_kriskura@quicinc.com/ 
from Krishna K, introduced a dt property 'wakeup-source' which indicates 
a platforms capability to handle wakeup interrupts. Based on this 
property, glue drivers can inform dwc3 core that the device is wakeup 
capable through device_init_wakeup(). For example dwc3-qcom driver 
informs it like below as per the implementation done in the above series

	wakeup_source = of_property_read_bool(dev->of_node, "wakeup-source");
	device_init_wakeup(&pdev->dev, wakeup_source);
	device_init_wakeup(&qcom->dwc3->dev, wakeup_source);

The dwc3 core now can access this info through 
device_may_wakeup(dwc->dev) while checking for bus suspend scenario to 
know whether the platform is capable of detecting wakeup.

Please let me know your thoughts on this approach.

Thanks
Elson