linux-kernel - Re: [RESEND PATCH 1/3] usb: dwc3: Don't reinitialize core during host bus-suspend/resume

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Message-ID: <87r2qwyfp9.fsf@linux.intel.com>
Date:   Thu, 11 Jan 2018 10:14:58 +0200
From:   Felipe Balbi <balbi@...nel.org>
To:     Manu Gautam <mgautam@...eaurora.org>, Roger Quadros <rogerq@...com>
Cc:     linux-arm-msm@...r.kernel.org, linux-usb@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        open list <linux-kernel@...r.kernel.org>,
        linux-omap <linux-omap@...r.kernel.org>
Subject: Re: [RESEND PATCH 1/3] usb: dwc3: Don't reinitialize core during host bus-suspend/resume


Hi,

Manu Gautam <mgautam@...eaurora.org> writes:
>> On 27/09/17 14:19, Manu Gautam wrote:
>>> Driver powers-off PHYs and reinitializes DWC3 core and gadget on
>>> resume. While this works fine for gadget mode but in host
>>> mode there is not re-initialization of host stack. Also, resetting
>>> bus as part of bus_suspend/resume is not correct which could affect
>>> (or disconnect) connected devices.
>>> Fix this by not reinitializing core on suspend/resume in host mode
>>> for HOST only and OTG/drd configurations.
>>>
>> All this seems correct but we (TI) were relying on dwc3_core_exit() to be called
>> during dwc3_suspend() to have the lowest power state for our platforms.
>>
>> After this patch, DWC3 controller and PHYs won't be turned off thus
>> preventing our platform from reaching low power levels.
>>
>> So this is a regression for us (TI) in v4.15-rc.
>>
>> Felipe, do you agree?
>>
>> If yes I can send a patch which fixes the regression
>> and also makes USB host work after suspend/resume.
>>
>
> I think it will be better to separate runtime_suspend and pm_suspend handling for
> host mode in dwc3. Powering offf/on PHYs and dwc3_core_exit/init across system
> suspend-resume should be ok but doing that for runtime suspend-resume is not
> correct.

it sure is. It's part of hibernation-while-disconnected programming sequence

> Let me know if that sounds ok, I can provide a patch for same instead of
> reverting this which affects runtime PM with dwc3 host.

nope, that would break platforms using hibernation

-- 
balbi

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