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

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Date:   Mon, 07 Sep 2020 10:44:55 +0300
From:   Felipe Balbi <balbi@...nel.org>
To:     Mike Looijmans <mike.looijmans@...ic.nl>,
        Mark Brown <broonie@...nel.org>
Cc:     Vincent Whitchurch <vincent.whitchurch@...s.com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        gregkh@...uxfoundation.org, lgirdwood@...il.com
Subject: Re: [PATCH v3] usb: dwc3: Add support for VBUS power control


Hi,

Mike Looijmans <mike.looijmans@...ic.nl> writes:
> 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 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.

you're perfectly okay with break all existing users of the driver?
That's a bit harsh

-- 
balbi

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