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

[Mike Looijmans]

Met vriendelijke groet / kind regards,

Mike Looijmans
System Expert


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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.