[U-Boot] [PATCH v4 10/20] tegra: fdt: Add additional USB binding

[Simon Glass]

Hi Olof,

On Wed, Jan 18, 2012 at 9:35 PM, Olof Johansson <olof at lixom.net> wrote:
> On Wed, Jan 18, 2012 at 03:48:30PM -0700, Stephen Warren wrote:
>> On 01/11/2012 09:32 PM, Simon Glass wrote:
>> > This adds a property to indicate a port which can switch between host and device
>> > mode.
>> >
>> > Signed-off-by: Simon Glass <sjg at chromium.org>
>> > ---
>> >
>> >  doc/device-tree-bindings/usb/tegra-usb.txt |    4 ++++
>> >  1 files changed, 4 insertions(+), 0 deletions(-)
>> >
>> > diff --git a/doc/device-tree-bindings/usb/tegra-usb.txt b/doc/device-tree-bindings/usb/tegra-usb.txt
>> > index 035d63d..96fd022 100644
>> > --- a/doc/device-tree-bindings/usb/tegra-usb.txt
>> > +++ b/doc/device-tree-bindings/usb/tegra-usb.txt
>> > @@ -11,3 +11,7 @@ Required properties :
>> >   - phy_type : Should be one of "ulpi" or "utmi".
>> >   - nvidia,vbus-gpio : If present, specifies a gpio that needs to be
>> >     activated for the bus to be powered.
>> > +
>> > +Optional properties:
>> > + - support-host-mode : If present then this peripheral can switch between
>> > +   host and device mode
>>
>> All of Tegra's USB ports support host mode, and it's the typical mode of
>> operation. The TRM also indicates that all USB ports support device mode
>> (possibly depending on the PHY type that's been selected for or attached
>> to port). Port 2 explicitly doesn't support run-time switching, but by
>> omission, ports 1 and 3 do.
>>
>> Hence, "support-host-mode" is not an accurate name, and doesn't match
>> the description given either.
>>
>> I think that it'd be better to:
>> * Add properties to explicitly specify whether the port is
>> intended/allowed to operate (per board design) in each of host or device
>> mode.
>> * Default to static host mode if no properties are present.
>>
>> i.e.:
>>
>> +Optional properties:
>> + - enable-host-mode : Indicate that the port is intended to operate in
>> +   host mode.
>> + - enable-device-mode : Indicate that the port is intended to operate
>> +   in device mode.
>
> fsl-usb.txt uses "dr_mode" here, which might make sense to reuse given some of
> the shared IP in question for device mode:
>
>  - dr_mode : indicates the working mode for "fsl-usb2-dr" compatible
>   controllers.  Can be "host", "peripheral", or "otg".  Default to
>   "host" if not defined for backward compatibility.

What does 'dr' mean?

Regards,
Simon

>
>
> -Olof