[PATCH v4 10/20] tegra: fdt: Add additional USB binding
Olof Johansson
olof at lixom.net
Thu Jan 19 16:35:23 EST 2012
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.
-Olof
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