[U-Boot] [PATCH] tegra20: usb: rework set_host_mode

[Stephen Warren]

On 08/07/2012 02:35 PM, Lucas Stach wrote:
> Am Dienstag, den 07.08.2012, 14:21 -0600 schrieb Stephen Warren:
>> On 08/07/2012 12:19 PM, Lucas Stach wrote:
>>> This allows for two things:
>>> - VBus GPIO may be used on other ports than the OTG one
>>> - VBus GPIO may be low active if specified by DT
>>
>> Hmmm. Why would the board have control over whether VBUS is asserted if
>> the port isn't intended to operate in OTG mode?
>>
>> Perhaps power-saving? In that case, I wonder if representing this as a
>> regulator rather than as a VBUS GPIO would make more sense?
>>
>> But irrespective of those questions, I'm inclined to think the patch is
>> probably OK.
>>
> On Colibri the second USB Port is powered down by default and only
> powered up if we are really going to use it. And the GPIO does exactly
> what it tells you from it's name: turn on VBus by triggering the USB
> power switch.

It's probably fine to do this; the kernel also unconditionally sets up
the VBUS GPIO irrespective of USB port mode.

> Thinking about a regulator for this in U-Boot is a bit of an overkill,
> for the Linux kernel this might be another story.

Device tree content isn't supposed to be influence by the consumer; it
should be identical irrespective of which bootloader/OS/... is using it.

So, in the future I expect this to be reworked to get rid of the
vbus-gpio property and replace it with a regulator.