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

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Message-ID: <0039d36f-dfca-44e7-9898-11f9e3eb9b9d@kernel.org>
Date: Tue, 2 Dec 2025 10:33:14 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Roy Luo <royluo@...gle.com>,
 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 02/12/2025 10:01, Roy Luo wrote:
> 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

The problem is not in Greg's solution but your code:
	depends on COMPILE_TEST

which makes absolutely no sense because it means this cannot be used
anywhere (in reasonable terms).


> 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
> 


No, instead depends ARCH_foo || COMPILE_TEST

and drop all other dependencies. You don't need them.


Best regards,
Krzysztof