linux-kernel - Re: [PATCH v9 2/2] usb: dwc3: Add Google Tensor SoC DWC3 glue driver

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Message-ID: <CA+zupgwgfKwPYqj8G2tNf4pEXNEWA+vL2WYJPhJ16xExgko7Dw@mail.gmail.com>
Date: Thu, 18 Dec 2025 11:02:28 -0800
From: Roy Luo <royluo@...gle.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Doug Anderson <dianders@...gle.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Peter Griffin <peter.griffin@...aro.org>, André Draszik <andre.draszik@...aro.org>, 
	Tudor Ambarus <tudor.ambarus@...aro.org>, Thinh Nguyen <Thinh.Nguyen@...opsys.com>, 
	Philipp Zabel <p.zabel@...gutronix.de>, Badhri Jagan Sridharan <badhri@...gle.com>, linux-usb@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-samsung-soc@...r.kernel.org, 
	Joy Chakraborty <joychakr@...gle.com>, Naveen Kumar <mnkumar@...gle.com>
Subject: Re: [PATCH v9 2/2] usb: dwc3: Add Google Tensor SoC DWC3 glue driver

On Wed, Dec 17, 2025 at 11:06 PM Krzysztof Kozlowski <krzk@...nel.org> wrote:
>
> On 18/12/2025 02:34, Roy Luo wrote:
> > On Wed, Dec 17, 2025 at 12:14 PM Doug Anderson <dianders@...gle.com> wrote:
> >>
> >> Hi,
> >>
> >> On Wed, Dec 17, 2025 at 11:18 AM Roy Luo <royluo@...gle.com> wrote:
> >>>
> >>> On Wed, Dec 17, 2025 at 5:24 AM Greg Kroah-Hartman
> >>> <gregkh@...uxfoundation.org> wrote:
> >>>>
> >>>> On Thu, Dec 04, 2025 at 11:14:39PM -0800, Roy Luo wrote:
> >>>>> On Thu, Dec 4, 2025 at 10:05 PM Greg Kroah-Hartman
> >>>>> <gregkh@...uxfoundation.org> wrote:
> >>>>>>
> >>>>>> On Fri, Dec 05, 2025 at 02:26:38AM +0000, Roy Luo wrote:
> >>>>>>> +config USB_DWC3_GOOGLE
> >>>>>>> +     tristate "Google Platform"
> >>>>>>> +     depends on ARCH_GOOGLE || COMPILE_TEST
> >>>>>>
> >>>>>> There is no ARCH_GOOGLE in the tree now, so how is this supposed to
> >>>>>> work?  Shouldn't tools that check for "invalid config options" trigger
> >>>>>> on this?
> >>>>>>
> >>>>>> thanks,
> >>>>>>
> >>>>>> greg k-h
> >>>>>
> >>>>> Hi Greg,
> >>>>>
> >>>>> The menuconfig looks like the following and it doesn't complain:
> >>>>> | Symbol: ARCH_GOOGLE [=ARCH_GOOGLE]
> >>>>> | Type  : unknown
> >>>>> |
> >>>>> | Symbol: PHY_GOOGLE_USB [=y]
> >>>>> | Type  : tristate
> >>>>> | Defined at drivers/phy/Kconfig:104
> >>>>> |     Prompt: Google Tensor SoC USB PHY driver
> >>>>> |     Depends on: ARCH_GOOGLE || COMPILE_TEST [=y]
> >>>>>
> >>>>> According to Kconfig documentation [1], the unknown symbol
> >>>>> would simply be evaluated as an "n", which is what we want.
> >>>>> "Convert the symbol into an expression. Boolean and tristate
> >>>>> symbols are simply converted into the respective expression
> >>>>> values. All other symbol types result in ‘n’."
> >>>>>
> >>>>> In a different Kconfig documentation, an environment variable
> >>>>> "KCONFIG_WARN_UNKNOWN_SYMBOLS" is there to detect
> >>>>> undefined symbols in the "config input", but I can't find one that
> >>>>> catches undefined symbols in the Kconfig tree itself.
> >>>>>
> >>>>> That is, the tool seems to allow this.
> >>>>> However, if this turns out to be a major problem. I think we
> >>>>> can either:
> >>>>> - Remove ARCH_GOOGLE and leave COMPILE_TEST as
> >>>>>   the only dependency. Then add ARCH_GOOGLE back
> >>>>>   later once it's in the tree.
> >>>>
> >>>> Please do this.  I do not want to take patches that purposfully add
> >>>> dependencies on config options that might, or might not, appear in the
> >>>> future.  Please just remove all of the dependancies for now, as they are
> >>>> not needed, right?
> >>>>
> >>>> thanks,
> >>>>
> >>>> greg k-h
> >>>
> >>> Greg,
> >>>
> >>> Yes, we can remove ARCH_GOOGLE for now.
> >>> To clarify, we're not removing all of the dependencies, we still want
> >>> to keep COMPILE_TEST for build tests, right?
> >>> Please let me know if you think otherwise.
> >>
> >> I think you'd just remove all of them. Normally COMPILE_TEST just
> >> allows folks to compile stuff even when they don't want the ARCH. We
> >> can can add ARCH_GOOGLE back in later once the config exists.
> >>
> >> -Doug
> >
> > Doug,
> >
> > Thanks for chiming in. I'm hesitant to remove COMPILE_TEST
> > because Greg specifically requested its inclusion in v7 [1].
>
>
> What? No, that's not what Greg requested. Your COMPILE_TEST in current
> form helps nothing in build testing. It makes absolutely no sense at all.
>
> > Also it seems beneficial to get some build coverage before
> > ARCH_GOOGLE is officially added to the tree.
>
> And COMPILE_TEST like you wrote it does not give you that. Please first
> read how this function works.
>
> > Greg, could you clarify?
>
> Can you first look at Linux kernel sources to see how this is properly
> written?
>
> >
> > [1] https://lore.kernel.org/linux-usb/2025112144-claw-recolor-49c3@gregkh/
> >
> > Thanks,
> > Roy
>
>
> Best regards,
> Krzysztof

Greg and Krzysztof,

Thanks for the clarification.

Regards,
Roy