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

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Date:   Wed, 17 Jun 2020 16:38:11 +0200
From:   Mike Looijmans <mike.looijmans@...ic.nl>
To:     Rob Herring <robh@...nel.org>
CC:     linux-usb@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
        balbi@...nel.org
Subject: Re: [PATCH v2] usb: dwc3: Add support for VBUS power control


Met vriendelijke groet / kind regards,

Mike Looijmans
System Expert


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T: +31 (0) 499 33 69 69
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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@...ic.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.

Or is it the intention that I write a usb-X-connector device driver 
first that handles the vbus?

-- 
Mike Looijmans