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Date:   Tue, 30 Apr 2019 06:05:21 +0000
From:   Artur Petrosyan <>
To:     Doug Anderson <>
CC:     Minas Harutyunyan <>,
        Felipe Balbi <>,
        "" <>,
        "Alan Stern" <>,
        "" <>,
        William Wu <>,
        "" <>,
        Stefan Wahren <>,
        Randy Li <>,
        "" <>,
        "" <>,
        "" <>,
        Amelie Delaunay <>,
        "" <>,
        "" <>,
        "Elaine Zhang" <>,
        Greg Kroah-Hartman <>,
        "" <>
Subject: Re: [PATCH v2 1/5] usb: dwc2: bus suspend/resume for hosts with


On 4/29/2019 21:34, Doug Anderson wrote:
> Hi,
> On Mon, Apr 29, 2019 at 1:43 AM Artur Petrosyan
> <> wrote:
>> Hi,
>> On 4/18/2019 04:15, Douglas Anderson wrote:
>>> This is an attempt to rehash commit 0cf884e819e0 ("usb: dwc2: add bus
>>> suspend/resume for dwc2") on ToT.  That commit was reverted in commit
>>> b0bb9bb6ce01 ("Revert "usb: dwc2: add bus suspend/resume for dwc2"")
>>> because apparently it broke the Altera SOCFPGA.
>>> With all the changes that have happened to dwc2 in the meantime, it's
>>> possible that the Altera SOCFPGA will just magically work with this
>>> change now.  ...and it would be good to get bus suspend/resume
>>> implemented.
>>> This change is a forward port of one that's been living in the Chrome
>>> OS 3.14 kernel tree.
>>> Signed-off-by: Douglas Anderson <>
>>> ---
>>> This patch was last posted at:
>>> ...and appears to have died the death of silence.  Maybe it could get
>>> some bake time in linuxnext if we can't find any proactive testing?
>>> I will also freely admit that I don't know tons about the theory
>>> behind this patch.  I'm mostly just re-hashing the original commit
>>> from Kever that was reverted since:
>>> * Turning on partial power down on rk3288 doesn't "just work".  I
>>>     don't get hotplug events.  This is despite dwc2 auto-detecting that
>>>     we are power optimized.
>> What do you mean by doesn't "just work" ? It seem to me that even after
>> adding this patch you don't get issues fixed.
>> You mention that you don't get the hotplug events. Please provide dwc2
>> debug logs and register dumps on this issue.
> I mean that partial power down in the currently upstream driver
> doesn't work.  AKA: if I turn on partial power down in the upstream
> driver then hotplug events break.  I can try to provide some logs.  On
> what exact version of the code do you want logs?  Just your series?
> Just my series?  Mainline?  Some attempt at combining both series?  As
> I said things seem to sorta work with the combined series.  I can try
> to clarify if that's the series you want me to test with.  ...or I can
> wait for your next version?
As I said this patch doesn't fix the issue with hotplug. With this patch 
or without the hotplug behaves as it was. I have tested it on our setup.

Have you debugged your patch? Does it make any difference on your setup 
? Does it fix the issue with hotplug?

Try to debug with the following steps.
1. Debug code with just your patch. Capture the logs and provide. So 
that I can see what is difference with your patch.
2. Debug only with my series and see if those issues with hotplug are 
still there.

>>> @@ -4506,21 +4507,35 @@ static int _dwc2_hcd_suspend(struct usb_hcd *hcd)
>>>         */
>>>        if (!hsotg->bus_suspended) {
>>>                hprt0 = dwc2_read_hprt0(hsotg);
>>> -             hprt0 |= HPRT0_SUSP;
>>> -             hprt0 &= ~HPRT0_PWR;
>>> -             dwc2_writel(hsotg, hprt0, HPRT0);
>>> -             spin_unlock_irqrestore(&hsotg->lock, flags);
>>> -             dwc2_vbus_supply_exit(hsotg);
>>> -             spin_lock_irqsave(&hsotg->lock, flags);
>>> +             if (hprt0 & HPRT0_CONNSTS) { > +                        hprt0 |= HPRT0_SUSP;
>> Here you set "HPRT0_SUSP" bit but what if core doesn't support both
>> hibernation and Partial Power down assuming that
>> hsotg->params.power_down" value us equal to "DWC2_POWER_DOWN_PARAM_NONE"
>> which is 0.
> I am by no means an expert on dwc2, but an assumption made in my patch
> is that even cores that can't support partial power down can still
> save some amount of power when hcd_suspend is called.
Have you tried to debug dwc2 with power_down == DWC2_POWER_DOWN_PARAM_NONE ?
> Some evidence that this should be possible: looking at mainline Linux
> and at dwc2_port_suspend(), I see:
> * It is currently called even when we have DWC2_POWER_DOWN_PARAM_NONE
Currently (without your and my patches) (looking at mainline Linux) the 
function dwc2_port_suspend() is called anyway because its call is issued 
by the system. But it performs entering to suspend only in case of 

This is not an assumption. What I am pointing out is based on debugging 
and before making assumptions without debugging for me seems not ok.

Currently without your patch and without my patches. In the 
dwc2_port_suspend() it will enter to suspend only in case that 
power_down == DWC2_POWER_DOWN_PARAM_PARTIAL. Because if you look at the 
code more carefully you will see

  	if (hsotg->params.power_down != DWC2_POWER_DOWN_PARAM_PARTIAL)
		goto skip_power_saving;

This says if power_down is not DWC2_POWER_DOWN_PARAM_PARTIAL then skip 
power saving.

So but after your patch. If power_down is DWC2_POWER_DOWN_PARAM_NONE it 
tries to suspend.

> * It currently sets HPRT0_SUSP
> * It currently sets PCGCTL_STOPPCLK specifically in the case where
> power down is DWC2_POWER_DOWN_PARAM_NONE.
It currently (without my and your patches) doesn't set PCGCTL_STOPPCLK 
when power down is DWC2_POWER_DOWN_PARAM_NONE. Because again and again 
when power down is DWC2_POWER_DOWN_PARAM_NONE power saving is skipped.

> ...I believe that the net effect of my patch ends up doing both those
> same two things in hcd_suspend.  That is: when power_down is
> DWC2_POWER_DOWN_PARAM_NONE I believe my patch is really just doing the
> same thing that dwc2_port_suspend() would do in the same case.  Is
> that not OK?
No if your patch is doing the same thing as it was doing before what is 
the purpose of the patch ?

My testes show that your patch doesn't fix the issue related partial 
power down.

>>> +                     if (hsotg->params.power_down == DWC2_POWER_DOWN_PARAM_PARTIAL)
>> You make one checking of hsotg->params.power_down mode here.
>>> +                             hprt0 &= ~HPRT0_PWR;
>>> +                     dwc2_writel(hsotg, hprt0, HPRT0);
>>> +             }
>>> +             if (hsotg->params.power_down == DWC2_POWER_DOWN_PARAM_PARTIAL) {
>> another checking of power_down mode here.
> Yeah, we can debate about how to best share/split code.  I'm not in
> love with the current structure either.  When I rebased your patches
> atop mine I changed this to more fully split them and I agree that was
> better.
>>> @@ -4592,10 +4612,12 @@ static int _dwc2_hcd_resume(struct usb_hcd *hcd)
>>>                spin_unlock_irqrestore(&hsotg->lock, flags);
>>>                dwc2_port_resume(hsotg);
>>>        } else {
>>> -             dwc2_vbus_supply_init(hsotg);
>>> +             if (hsotg->params.power_down == DWC2_POWER_DOWN_PARAM_PARTIAL) {
>>> +                     dwc2_vbus_supply_init(hsotg);
>>> -             /* Wait for controller to correctly update D+/D- level */
>>> -             usleep_range(3000, 5000);
>>> +                     /* Wait for controller to correctly update D+/D- level */
>>> +                     usleep_range(3000, 5000);
>>> +             }
>>>                /*
>>>                 * Clear Port Enable and Port Status changes.
>> I have tested the patch on HAPS-DX. With this patch or without it when I
>> have a device connected core  enters to partial power down and doesn't
>> exit from it. So I cannot use the device.
> Can you explain what HAPS-DX is?
It is the general setup to perform our use case testes.
For more information about the details you can google about it.

> -Doug


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