Re: [PATCH v2 1/5] usb: dwc2: bus suspend/resume for hosts with DWC2_POWER_DOWN_PARAM_NONE

[Doug Anderson]

Hi,

On Fri, May 3, 2019 at 1:20 AM Artur Petrosyan
<Arthur.Petrosyan@xxxxxxxxxxxx> wrote:
>
> On 5/1/2019 05:57, Doug Anderson wrote:
> > Hi,
> >
> > On Mon, Apr 29, 2019 at 11:06 PM Artur Petrosyan
> > <Arthur.Petrosyan@xxxxxxxxxxxx> wrote:
> >>
> >> Hi,
> >>
> >> On 4/29/2019 21:34, Doug Anderson wrote:
> >>> Hi,
> >>>
> >>> On Mon, Apr 29, 2019 at 1:43 AM Artur Petrosyan
> >>> <Arthur.Petrosyan@xxxxxxxxxxxx> 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 <dianders@xxxxxxxxxxxx>
> >>>>> ---
> >>>>> This patch was last posted at:
> >>>>>
> >>>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__lkml.kernel.org_r_1446237173-2D15263-2D1-2Dgit-2Dsend-2Demail-2Ddianders-40chromium.org&d=DwIDAg&c=DPL6_X_6JkXFx7AXWqB0tg&r=9hPBFKCJ_nBjJhGVrrlYOeOQjP_HlVzYqrC_D7niMJI&m=MMfe-4lZePyty6F5zfQ54kiYGuJWNulyRat944LkOsc&s=nExFpAPP_0plZfO5LMG1B-mqt1vyCvE35elVcyVgs8Y&e=
> >>>>>
> >>>>> ...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?
> >
> > I think we're still not taking on the same page.
> >
> > My patch makes no attempt to make partial power down mode work.  My
> > patch attempts to make things work a little better when using
> > DWC2_POWER_DOWN_PARAM_NONE.  There is no use testing my patch with
> > partial power down as it shouldn't have any impact there.
> >
> >
> >>> 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
> >> DWC2_POWER_DOWN_PARAM_PARTIAL.
> >>
> >> 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.
> >
> > We must be looking at different code.  I'm looking at Linux's tree, AKA:
> >
> > https://urldefense.proofpoint.com/v2/url?u=https-3A__git.kernel.org_pub_scm_linux_kernel_git_torvalds_linux.git_tree_drivers_usb_dwc2_hcd.c-23n3488&d=DwIFaQ&c=DPL6_X_6JkXFx7AXWqB0tg&r=9hPBFKCJ_nBjJhGVrrlYOeOQjP_HlVzYqrC_D7niMJI&m=IWkDOOGTr0q-H1piDv2KOZe_Hnrz18g6rXFx-DsTuv4&s=AHu2iOKkybliRGtIfN7cF5p070UdvUKTYJsyAKYojis&e=
> Here you are looking at the old code. After that there are several of
> changes related to suspend/resume functions.

In my email, see that I said I actually checked out mainline kernel
(and I gave you the exact version: "v5.1-rc7-5-g83a50840e72a") and
added printouts in dwc2_port_suspend() next to where it set HPRT0_SUSP
and PCGCTL_STOPPCLK in dwc2_port_suspend().

[  454.906364] dwc2 ff540000.usb: I'm setting HPRT0_SUSP
[  454.906367] dwc2 ff540000.usb: I'm setting PCGCTL_STOPPCLK

The version "v5.1-rc7-5-g83a50840e72a" is not old code.


> This is the link to the code with changes. Latest version of those
> functions.
>
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/usb/dwc2/hcd.c#n4489
>
> Your changes are sitting on that latest version of code. Not the old
> version of it.

You are pointing me at _dwc2_hcd_suspend() whereas I pointed at
dwc2_port_suspend().  Why?

I am saying that dwc2_port_suspend() _does_ set "HPRT0_SUSP" and
"PCGCTL_STOPPCLK" even with DWC2_POWER_DOWN_PARAM_NONE.  Do you
disagree?

I completely agree that on mainline _dwc2_hcd_suspend() _does not_ set
these bits with DWC2_POWER_DOWN_PARAM_NONE.  That is what my patch
fixes.


-Doug