linux-kernel - Re: [PATCH v3] usb: dwc3: Add support for VBUS power control

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Message-ID: <a6821b3d-4034-8399-af5e-1b9de0493eac@topic.nl>
Date:   Tue, 28 Jul 2020 09:29:39 +0200
From:   Mike Looijmans <mike.looijmans@...ic.nl>
To:     Mark Brown <broonie@...nel.org>
CC:     Vincent Whitchurch <vincent.whitchurch@...s.com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        balbi@...nel.org, gregkh@...uxfoundation.org, lgirdwood@...il.com
Subject: Re: [PATCH v3] usb: dwc3: Add support for VBUS power control


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@...icproducts.com
W: www.topicproducts.com

Please consider the environment before printing this e-mail
On 27-07-2020 13:53, Mark Brown wrote:
> On Mon, Jul 27, 2020 at 01:50:26PM +0200, Mike Looijmans wrote:
>>
>> Met vriendelijke groet / kind regards,
>>
>> Mike Looijmans
>> System Expert
> 
> You probably want to remove your signature when replying to the list...
> 
>> On 27-07-2020 12:23, Mark Brown wrote:
>>> On Sun, Jul 26, 2020 at 09:10:39AM +0200, Mike Looijmans wrote:
> 
>>>> It's the 5V VBUS power for the USB "plug" that's being controlled here. It
>>>> must turned on when the controller is in "host" mode. Some boards arrange
>>>> this in hardware through the PHY, and some just don't have any control at
>>>> all and have it permanently on or off. On a board where the 5V is controlled
>>>> using a GPIO line or an I2C chip, this patch is required to make it work.
> 
>>> That sounds like the driver should not be using _get_optional() then.
> 
>> Making it mandatory would break most (read: all except Topic's) existing
>> boards as they won't have it in their devicetree. I'm perfectly okay with
>> that, but others might disagree.
> 
> No, it wouldn't break them at all - they'd get a dummy regulator
> provided.
> 

Ah, so *not* using _get_optional will yield the behaviour that I'd want. I'll 
test and make a v4 patch.