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

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Date:   Mon, 27 Jul 2020 11:23:17 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Mike Looijmans <mike.looijmans@...ic.nl>
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

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.

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