linux-kernel - Re: [PATCH 3/6] usb: cdns3-ti: add suspend/resume procedures for J7200

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Message-ID: <6a8c44e1-d3a3-49ee-bfbc-8a994a6d4ff8@kernel.org>
Date:   Sat, 18 Nov 2023 12:41:07 +0200
From:   Roger Quadros <rogerq@...nel.org>
To:     Théo Lebrun <theo.lebrun@...tlin.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Peter Chen <peter.chen@...nel.org>,
        Pawel Laszczak <pawell@...ence.com>,
        Nishanth Menon <nm@...com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Tero Kristo <kristo@...nel.org>,
        "Vardhan, Vibhore" <vibhore@...com>
Cc:     linux-usb@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Grégory Clement <gregory.clement@...tlin.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH 3/6] usb: cdns3-ti: add suspend/resume procedures for
 J7200



On 17/11/2023 16:20, Théo Lebrun wrote:
> Hi Roger,
> 
> On Fri Nov 17, 2023 at 12:51 PM CET, Roger Quadros wrote:
>> On 17/11/2023 12:17, Théo Lebrun wrote:
>>> On Thu Nov 16, 2023 at 10:44 PM CET, Roger Quadros wrote:
>>>> On 16/11/2023 20:56, Théo Lebrun wrote:
>>>>> On Thu Nov 16, 2023 at 1:40 PM CET, Roger Quadros wrote:
>>>>>> On 15/11/2023 17:02, Théo Lebrun wrote:
>>>>>>> On Wed Nov 15, 2023 at 12:37 PM CET, Roger Quadros wrote:
>>>>>>>> You might want to check suspend/resume ops in cdns3-plat and
>>>>>>>> do something similar here.
>>>>>>>
>>>>>>> I'm unsure what you are referring to specifically in cdns3-plat?
>>>>>>
>>>>>> What I meant is, calling pm_runtime_get/put() from system suspend/resume
>>>>>> hooks doesn't seem right.
>>>>>>
>>>>>> How about using something like pm_runtime_forbid(dev) on devices which
>>>>>> loose USB context on runtime suspend e.g. J7200.
>>>>>> So at probe we can get rid of the pm_runtime_get_sync() call.
>>>>>
>>>>> What is the goal of enabling PM runtime to then block (ie forbid) it in
>>>>> its enabled state until system suspend?
>>>>
>>>> If USB controller retains context on runtime_suspend on some platforms
>>>> then we don't want to forbid PM runtime.
>>>
>>> What's the point of runtime PM if nothing is done based on it? This is
>>> the current behavior of the driver.
>>
>> Even if driver doesn't have runtime_suspend/resume hooks, wouldn't 
>> the USB Power domain turn off if we enable runtime PM and allow runtime
>> autosuspend and all children have runtime suspended?
> 
> That cannot be the currently desired behavior as it would require a
> runtime_resume implementation that restores this wrapper to its desired
> state.
> 
> It could however be something that could be implemented. It would be a
> matter of enabling PM runtime and that is it in the probe. No need to
> even init the hardware in the probe. Then the runtime_resume
> implementation would call the new cdns_ti_init_hw.
> 
> This is what the cdns3-imx wrapper is doing in a way, though what they
> need is clocks rather than some registers to be written.
> 
> That all feels like outside the scope of the current patch series
> though.
> 
> My suggestion for V2 would still therefore be to remove all PM runtime
> as it has no impact. It could be added later down the road if cutting
> the power-domain is a goal of yours.

OK let's do this.

-- 
cheers,
-roger