linux-kernel - Re: [PATCH v8 2/2] usb: dwc3: Add Google Tensor SoC DWC3 glue driver

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Message-ID: <CA+zupgwzQ5r=-_L79D74=9VRqRO94N0yTApHChM+Nu0cn1ss3w@mail.gmail.com>
Date: Tue, 2 Dec 2025 03:01:13 -0600
From: Roy Luo <royluo@...gle.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: 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>, 
	Doug Anderson <dianders@...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 v8 2/2] usb: dwc3: Add Google Tensor SoC DWC3 glue driver

On Sat, Nov 22, 2025 at 8:59 PM Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
>
> On Sat, Nov 22, 2025 at 09:32:06AM +0000, Roy Luo wrote:
> > Add support for the DWC3 USB controller found on Google Tensor G5
> > (codename: laguna). The controller features dual-role functionality
> > and hibernation.
> >
> > The primary focus is implementing hibernation support in host mode,
> > enabling the controller to enter a low-power state (D3). This is
> > particularly relevant during system power state transition and
> > runtime power management for power efficiency.
> > Highlights:
> > - Align suspend callback with dwc3_suspend_common() for deciding
> >   between a full teardown and hibernation in host mode.
> > - Integration with `psw` (power switchable) and `top` power domains,
> >   managing their states and device links to support hibernation.
> > - A notifier callback dwc3_google_usb_psw_pd_notifier() for
> >   `psw` power domain events to manage controller state
> >   transitions to/from D3.
> > - Coordination of the `non_sticky` reset during power state
> >   transitions, asserting it on D3 entry and deasserting on D0 entry
> >   in hibernation scenario.
> > - Handling of high-speed and super-speed PME interrupts
> >   that are generated by remote wakeup during hibernation.
> >
> > Co-developed-by: Joy Chakraborty <joychakr@...gle.com>
> > Signed-off-by: Joy Chakraborty <joychakr@...gle.com>
> > Co-developed-by: Naveen Kumar <mnkumar@...gle.com>
> > Signed-off-by: Naveen Kumar <mnkumar@...gle.com>
> > Signed-off-by: Roy Luo <royluo@...gle.com>
> > ---
> >  drivers/usb/dwc3/Kconfig       |  13 +
> >  drivers/usb/dwc3/Makefile      |   1 +
> >  drivers/usb/dwc3/dwc3-google.c | 628 +++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 642 insertions(+)
> >
> > diff --git a/drivers/usb/dwc3/Kconfig b/drivers/usb/dwc3/Kconfig
> > index 4925d15084f816d3ff92059b476ebcc799b56b51..f58c70dabf108878cbefe0abea88572d9ae81e26 100644
> > --- a/drivers/usb/dwc3/Kconfig
> > +++ b/drivers/usb/dwc3/Kconfig
> > @@ -200,4 +200,17 @@ config USB_DWC3_GENERIC_PLAT
> >         the dwc3 child node in the device tree.
> >         Say 'Y' or 'M' here if your platform integrates DWC3 in a similar way.
> >
> > +config USB_DWC3_GOOGLE
> > +     tristate "Google Platform"
> > +     depends on COMPILE_TEST
> > +     depends on OF && COMMON_CLK && RESET_CONTROLLER
>
> Shouldn't this be:
>         depends on (OF && COMMON_CLK && RESET_CONTROLLER) || COMPILE_TEST
>
> I shouldn't have to enable those options to just get a build test here,
> the apis should be properly stubbed out if those options are not
> enabled, right?
>
> thanks,
>
> greg k-h

Hi Greg,

I agree with your interpretation of COMPILE_TEST but it doesn't
seem to align with upstream convention. I found the following pattern
in several device driver Kconfig files (including but not limited to usb,
pinctrl and phy).

    depends on COMPILE_TEST || ARCH_XXX
    depends on CONFIG_A && CONFIG_B...

For this patch, the APIs exposed by OF, COMMON_CLK
and RESET_CONTROLLER are properly stubbed out so
I'm all good to go with your suggestion, but I'd like to make
sure this approach is conventional.

I plan to add ARCH_GOOGLE as a dependency in the next
version per [1], so the "depends on" would probably look like
the following per your suggestion:

    depends on (OF && COMMON_CLK && RESET_CONTROLLER && ARCH_GOOGLE)
|| COMPILE_TEST

Please let me know your thoughts.
[1] https://lore.kernel.org/linux-phy/1a53d473-fc13-4ac5-ba52-4701d95e3073@kernel.org/

Thanks,
Roy Luo