linux-kernel - Re: [PATCH v7] usb: dwc3: core: Workaround for CSR read timeout

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Message-ID: <CAMtoTm2UE31gcM7dGxvz_CbFoKotOJ1p7PeQwgBuTDE9nq7CJw@mail.gmail.com>
Date: Tue, 25 Jun 2024 20:23:06 +0800
From: joswang <joswang1221@...il.com>
To: Thinh Nguyen <Thinh.Nguyen@...opsys.com>, Greg KH <gregkh@...uxfoundation.org>
Cc: "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"stable@...r.kernel.org" <stable@...r.kernel.org>, Jos Wang <joswang@...ovo.com>
Subject: Re: [PATCH v7] usb: dwc3: core: Workaround for CSR read timeout

On Sat, Jun 22, 2024 at 7:09 AM Thinh Nguyen <Thinh.Nguyen@...opsys.com> wrote:
>
> On Fri, Jun 21, 2024, Greg KH wrote:
> > On Fri, Jun 21, 2024 at 06:20:38AM +0000, Thinh Nguyen wrote:
> > > On Fri, Jun 21, 2024, Greg KH wrote:
> > > > On Fri, Jun 21, 2024 at 05:42:42AM +0000, Thinh Nguyen wrote:
> > > > > On Fri, Jun 21, 2024, Greg KH wrote:
> > > > > > On Fri, Jun 21, 2024 at 09:40:10AM +0800, joswang wrote:
> > > > > > > On Fri, Jun 21, 2024 at 1:16 AM Greg KH <gregkh@...uxfoundation.org> wrote:
> > > > > > > >
> > > > > > > > On Wed, Jun 19, 2024 at 07:45:29PM +0800, joswang wrote:
> > > > > > > > > From: Jos Wang <joswang@...ovo.com>
> > > > > > > > >
> > > > > > > > > This is a workaround for STAR 4846132, which only affects
> > > > > > > > > DWC_usb31 version2.00a operating in host mode.
> > > > > > > > >
> > > > > > > > > There is a problem in DWC_usb31 version 2.00a operating
> > > > > > > > > in host mode that would cause a CSR read timeout When CSR
> > > > > > > > > read coincides with RAM Clock Gating Entry. By disable
> > > > > > > > > Clock Gating, sacrificing power consumption for normal
> > > > > > > > > operation.
> > > > > > > > >
> > > > > > > > > Cc: stable@...r.kernel.org
> > > > > > > > > Signed-off-by: Jos Wang <joswang@...ovo.com>
> > > > > > > >
> > > > > > > > What commit id does this fix?  How far back should it be backported in
> > > > > > > > the stable releases?
> > > > > > > >
> > > > > > > > thanks,
> > > > > > > >
> > > > > > > > greg k-h
> > > > > > >
> > > > > > > Hello Greg Thinh
> > > > > > >
> > > > > > > It seems first begin from the commit 1e43c86d84fb ("usb: dwc3: core:
> > > > > > > Add DWC31 version 2.00a controller")
> > > > > > > in 6.8.0-rc6 branch ?
> > > > > >
> > > > > > That commit showed up in 6.9, not 6.8.  And if so, please resend with a
> > > > > > proper "Fixes:" tag.
> > > > > >
> > > > >
> > > > > This patch workarounds the controller's issue.
> > > >
> > > > So it fixes a bug?  Or does not fix a bug?  I'm confused.
> > >
> > > The bug is not a driver's bug. The fix applies to a hardware bug and not
> > > any particular commit that can be referenced with a "Fixes" tag.
> >
> > So it's a bug that the kernel needs to work around, that's fine.  But
> > that implies it should go to "all" stable kernels that it can, right?
>
> Yes. That's right.
>
> >
> > > > > It doesn't resolve any
> > > > > particular commit that requires a "Fixes" tag. So, this should go on
> > > > > "next". It can be backported as needed.
> > > >
> > > > Who would do the backporting and when?
> > >
> > > For anyone who doesn't use mainline kernel that needs this patch
> > > backported to their kernel version.
> >
> > I can not poarse this, sorry.  We can't do anything about people who
> > don't use our kernel trees, so what does this mean?
>
> Sorry, I wasn't being clear. What I meant is that it needs some work to
> backport to stable version prior to v6.9. Anyone who needs to backport
> this prior to this will need to resolve these dependencies.
>
> >
> > > > > If it's to be backported, it can
> > > > > probably go back to as far as v4.3, to commit 690fb3718a70 ("usb: dwc3:
> > > > > Support Synopsys USB 3.1 IP"). But you'd need to collect all the
> > > > > dependencies including the commit mention above.
> > > >
> > > > I don't understand, sorry.  Is this just a normal "evolve the driver to
> > > > work better" change, or is it a "fix broken code" change, or is it
> > > > something else?
> > > >
> > > > In other words, what do you want to see happen to this?  What tree(s)
> > > > would you want it applied to?
> > > >
> > >
> > > It's up to you, but it seems to fit "usb-testing" branch more since it
> > > doesn't have a "Fixes" tag. The severity of this fix is debatable since
> > > it doesn't apply to every DWC_usb31 configuration or every scenario.
> >
> > As it is "cc: stable" that implies that it should get to Linus for
> > 6.10-final, not wait for 6.11-rc1 as the 6.11 release is months away,
> > and anyone who has this issue would want it fixed sooner.
> >
> > still confused,
> >
>
> Ok. I may have misunderstood what can go into rc2 and beyond then. If we
> don't have to wait for the next rc1 for it to be picked up for stable,
> then can we add it to "usb-linus" branch?
>
> There won't be a Fixes tag, but we can backport it up to 5.10.x:
>
> Cc: <stable@...r.kernel.org> # 5.10.x: 1e43c86d: usb: dwc3: core: Add DWC31 version 2.00a controller
> Cc: <stable@...r.kernel.org> # 5.10.x
>
> This can go after the versioning scheme in dwc3 in the 5.10.x lts. I did
> not check what other dependencies are needed in addition to the change
> above.
>
> Thanks,
> Thinh

Is there anything else I need to modify for this patch?

Thanks,
Jos Wang