Re: [PATCH v2] usb: dwc3: Add support for VBUS power control

[Mike Looijmans <mike.looijmans@topic.nl>]

Met vriendelijke groet / kind regards,

Mike Looijmans
System Expert


TOPIC Embedded Products B.V.
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On 17-06-2020 18:13, Rob Herring wrote:
> On Wed, Jun 17, 2020 at 8:38 AM Mike Looijmans <mike.looijmans@topic.nl> wrote:
>>
>> Met vriendelijke groet / kind regards,
>>
>> Mike Looijmans
>> System Expert
>>
>>
>> TOPIC Embedded Products B.V.
>> Materiaalweg 4, 5681 RJ Best
>> The Netherlands
>>
>> T: +31 (0) 499 33 69 69
>> E: mike.looijmans@topicproducts.com
>> W: www.topicproducts.com
>>
>> Please consider the environment before printing this e-mail
>> On 10-06-2020 22:22, Rob Herring wrote:
>>> On Wed, Jun 03, 2020 at 02:09:15PM +0200, Mike Looijmans wrote:
>>>> Support VBUS power control using regulator framework. Enables the regulator
>>>> while the port is in host mode.
>>>>
>>>> Signed-off-by: Mike Looijmans <mike.looijmans@topic.nl>
>>>> ---
>>>> v2: Add missing devm_regulator_get call which got lost during rebase
>>>>
>>>>    .../devicetree/bindings/usb/dwc3.txt          |  1 +
>>>>    drivers/usb/dwc3/core.c                       | 34 ++++++++++++++-----
>>>>    drivers/usb/dwc3/core.h                       |  4 +++
>>>>    drivers/usb/dwc3/drd.c                        |  6 ++--
>>>>    4 files changed, 33 insertions(+), 12 deletions(-)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/usb/dwc3.txt b/Documentation/devicetree/bindings/usb/dwc3.txt
>>>> index 9946ff9ba735..56bc3f238e2d 100644
>>>> --- a/Documentation/devicetree/bindings/usb/dwc3.txt
>>>> +++ b/Documentation/devicetree/bindings/usb/dwc3.txt
>>>> @@ -37,6 +37,7 @@ Optional properties:
>>>>     - phys: from the *Generic PHY* bindings
>>>>     - phy-names: from the *Generic PHY* bindings; supported names are "usb2-phy"
>>>>       or "usb3-phy".
>>>> + - vbus-supply: Regulator handle that provides the VBUS power.
>>> Does the DWC3 block require Vbus to power itself? Doubtful. This
>>> belongs in a usb-connector node. If the DWC3 driver wants to get the
>>> Vbus supply, it can fetch it from that node.
>>>
>>> Rob
>> Okay, I've been digging into that. But there's no actual driver that
>> binds to a "usb-b-connector" compatible, so how do we get to the
>> vbus-supply from there?
>>
>> [devm_]regulator_get only accepts a device as argument, and will not
>> look into child nodes. The only way to get at the vbus of a child node
>> (or a node linked through a port) would be to hand-code the equivalent
>> of of_regulator_get(), which will not be acceptable.
> Doesn't it look into child nodes calling of_get_child_regulator()?
Looking at the code in regulator/core.c, yeah, it should. I'll have to 
add some debugging lines and look into why it didn't work in my test.
> You're right that it wouldn't work if graph is used. The connector has
> to be either a child of a controller for the connector or the USB
> controller. I'd expect you'd have the former for Type-C, but for
> "usb-b-connector" the parent is more likely just the USB controller.
For my current case, using a direct child would be fine, there's nothing 
else connected. But I expect that we'll produce a board with some USB-C 
connector some day yeah.
>
> In any case, having a struct device shouldn't be a requirement and
> most subsystems expose a get function only needing the DT node.
>
>> Or is it the intention that I write a usb-X-connector device driver
>> first that handles the vbus?
> That's a kernel implementation detail that is independent of the
> binding, but yes we'll probably need a driver or library helper
> functions eventually. Note that it is possible to have a struct device
> without a driver.
>
> Rob


-- 
Mike Looijmans