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SubjectRe: [PATCH v3] usb: dwc3: Add support for VBUS power control
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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

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On 27-07-2020 12:23, Mark Brown wrote:
> On Sun, Jul 26, 2020 at 09:10:39AM +0200, Mike Looijmans wrote:
>> On 23-07-2020 13:05, Mark Brown wrote:
>
>>> Does the device actually support running without power so that's a thing
>>> that can happen? _get_optional() should only ever be used for supplies
>>> that may be physically absent.
>
>> 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.

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