linux-kernel - Re: [PATCH v2 1/5] usb: dwc2: bus suspend/resume for hosts with DWC2_POWER_DOWN_PARAM

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Message-ID: <CAD=FV=V97+_cQ1aD=w_a3SifGOG3M5DPvcnvxYVUJMkX_WLTFg@mail.gmail.com>
Date:   Fri, 3 May 2019 08:07:32 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Artur Petrosyan <Arthur.Petrosyan@...opsys.com>
Cc:     Minas Harutyunyan <Minas.Harutyunyan@...opsys.com>,
        Felipe Balbi <felipe.balbi@...ux.intel.com>,
        Heiko Stübner <heiko@...ech.de>,
        Alan Stern <stern@...land.harvard.edu>,
        Alexandru M Stan <amstan@...omium.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        William Wu <william.wu@...k-chips.com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        Stefan Wahren <stefan.wahren@...e.com>,
        Randy Li <ayaka@...lik.info>, Chris <zyw@...k-chips.com>,
        Matthias Kaehlcke <mka@...omium.org>,
        Ryan Case <ryandcase@...omium.org>,
        Amelie Delaunay <amelie.delaunay@...com>,
        Julius Werner <jwerner@...omium.org>,
        Elaine Zhang <zhangqing@...k-chips.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/5] usb: dwc2: bus suspend/resume for hosts with DWC2_POWER_DOWN_PARAM_NONE

Hi,

On Fri, May 3, 2019 at 1:25 AM Artur Petrosyan
<Arthur.Petrosyan@...opsys.com> wrote:
>
> On 5/2/2019 03:58, Doug Anderson wrote:
> > Hi,
> >
> >
> > On Wed, Apr 17, 2019 at 5:15 PM Douglas Anderson <dianders@...omium.org> 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@...omium.org>
> >> ---
> >> 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=DwIBaQ&c=DPL6_X_6JkXFx7AXWqB0tg&r=9hPBFKCJ_nBjJhGVrrlYOeOQjP_HlVzYqrC_D7niMJI&m=7rxT8EFX9mqUDtTL4P7iuzYNsYROe9rxHGCresSKPTg&s=lTaNUA2XIYPat417fkd1A4Zpvb5eyYtTc1H_NIfW8Vw&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.
> >> * If we don't do something like this commit we don't get into as low
> >>    of a power mode.
> >
> > OK, I spent the day digging more into this patch to confirm that it's
> > really the right thing to do.  ...and it still seems to be.
> >
> > First off: I'm pretty sure the above sentence "If we don't do
> > something like this commit we don't get into as low of a power mode."
> > is totally wrong.  Luckily it's "after the cut" and not part of the
> > commit message.  Specifically I did a bunch of power testing and I
> > couldn't find any instance saving power after this patch.
> >
> > ...but, then I looked more carefully at all the history of this
> > commit.  I ended up at:
> >
> > https://urldefense.proofpoint.com/v2/url?u=https-3A__chromium-2Dreview.googlesource.com_c_chromiumos_third-5Fparty_kernel_-2B_306265_&d=DwIBaQ&c=DPL6_X_6JkXFx7AXWqB0tg&r=9hPBFKCJ_nBjJhGVrrlYOeOQjP_HlVzYqrC_D7niMJI&m=7rxT8EFX9mqUDtTL4P7iuzYNsYROe9rxHGCresSKPTg&s=LiyyIyaCPmr88nJeI7TCGtoJBFLRWir_reikYtAHHDw&e=
> Looking at this code review I see that this patch fixes whatever issues
> you have on Chrome OS 3.14. But your patch has landed on the top of
> latest Kernel version. With the latest version I think you would not
> have the regression issue.
> So you are fixing Chrome OS 3.14.

I'm confused why you ignored the rest of my email where I said I also
ported it to 4.19 (which, from a dwc2 host point of view, is pretty
much mainline) and saw that the patch was still needed.

-Doug