linux-kernel - Re: [PATCH 1/3] doc: dt: bindings: usb: dwc3: Update entries for disabling SS instances in park mode

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Date:   Tue, 12 Nov 2019 09:48:22 +0800
From:   Jun Li <lijun.kernel@...il.com>
To:     Tim <elatllat@...il.com>
Cc:     Neil Armstrong <narmstrong@...libre.com>,
        Felipe Balbi <balbi@...nel.org>, khilman@...libre.com,
        devicetree@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Dongjin Kim <tobetter@...il.com>,
        Jianxin Pan <jianxin.pan@...ogic.com>,
        Rob Herring <robh@...nel.org>
Subject: Re: [PATCH 1/3] doc: dt: bindings: usb: dwc3: Update entries for
 disabling SS instances in park mode

by a quirk, those platforms without this quirk can't benefit this fix.

if later this bug is fixed by some reversion of dwc3 IP, we can easily
remove the workaround by a IP version check:
if (dwc->revision < DWC3_REVISION_PARK_MODE_FIXED)
{
          disable park mode for ss;
}

Li Jun

Tim <elatllat@...il.com> 于2019年11月11日周一 下午10:05写道：
>
> Speculation;
>
> Maybe the kernel maintainers prefer to optimistically permit future
> products to easily remove workarounds via quirk flags.
> Even if data from testing were shown, and it did not impact
> performance, code reduction and clarity are desirable.
>
> On Sun, Nov 10, 2019 at 8:58 PM Jun Li <lijun.kernel@...il.com> wrote:
> >
> > Hi Neil
> >
> > As I got the information from Synopsys, this bug exists on current IP versions,
> > and per my tests with external USB3 hub + 2 Super speed udisks on data
> > read by dd, I can reproduce this issue with different kernel versions, also I
> > didn't see obvious performance drop by dd tests after disable park mode for
> > super speed, so should we just disable it by default so no need a quirk?
> >
> > Li Jun
> >
> > Tim <elatllat@...il.com> 于2019年11月11日周一 上午8:42写道：
> > >
> > > Thanks for working on this Neil,
> > > Is there something that needs doing for this patch to make it into 5.3 or 5.4?
> > > As previously mentioned the patch set fixes the issue on affected hardware;
> > >     https://patchwork.kernel.org/patch/11164515/
> > >
> > >
> > >
> > > On Wed, Oct 23, 2019 at 4:11 PM Rob Herring <robh@...nel.org> wrote:
> > > >
> > > > On Mon, Oct 14, 2019 at 04:17:16PM +0200, Neil Armstrong wrote:
> > > > > This patch updates the documentation with the information related
> > > > > to the quirks that needs to be added for disabling all SuperSpeed XHCi
> > > > > instances in park mode.
> > > > >
> > > > > CC: Dongjin Kim <tobetter@...il.com>
> > > > > Cc: Jianxin Pan <jianxin.pan@...ogic.com>
> > > > > Reported-by: Tim <elatllat@...il.com>
> > > > > Signed-off-by: Neil Armstrong <narmstrong@...libre.com>
> > > > > ---
> > > > >  Documentation/devicetree/bindings/usb/dwc3.txt | 2 ++
> > > > >  1 file changed, 2 insertions(+)
> > > >
> > > > Sigh, what's one more to the never ending list of quirks...
> > > >
> > > > Acked-by: Rob Herring <robh@...nel.org>