[U-Boot] [PATCH 4/9] sunxi: Switch MUSB to gadget mode on the Bananapi M3

[Maxime Ripard]

On Fri, Sep 22, 2017 at 11:20:10AM +0000, Chen-Yu Tsai wrote:
> On Fri, Sep 22, 2017 at 4:14 PM, Maxime Ripard
> <maxime.ripard at free-electrons.com> wrote:
> > On Fri, Sep 22, 2017 at 07:26:30AM +0000, Chen-Yu Tsai wrote:
> >> The Bananapi M3 has a micro-USB OTG port. It supports both host and
> >> gadget mode. Having the OTG port operate in gadget mode is more useful,
> >> as we can use it for fastboot or Ethernet over USB.
> >>
> >> The board has 2 other USB host ports that are supported. These can be
> >> used for connecting peripherals.
> >>
> >> Signed-off-by: Chen-Yu Tsai <wens at csie.org>
> >> ---
> >>  configs/Sinovoip_BPI_M3_defconfig | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/configs/Sinovoip_BPI_M3_defconfig b/configs/Sinovoip_BPI_M3_defconfig
> >> index f321d94e04eb..e48983fc3310 100644
> >> --- a/configs/Sinovoip_BPI_M3_defconfig
> >> +++ b/configs/Sinovoip_BPI_M3_defconfig
> >> @@ -27,5 +27,5 @@ CONFIG_AXP_DCDC5_VOLT=1200
> >>  CONFIG_AXP_DLDO3_VOLT=2500
> >>  CONFIG_AXP_SW_ON=y
> >>  CONFIG_USB_EHCI_HCD=y
> >> -CONFIG_USB_MUSB_HOST=y
> >> +CONFIG_USB_MUSB_GADGET=y
> >
> > I wonder whether this could become the default.
> >
> > As far as I can see, having it as host can only be useful on the
> > tablets we support.
> >
> > Maybe we can add a config option for tablets device, and if it's set,
> > enable in host mode, and if not defaults to gadget.
> >
> > Eventually, we could move all the options that are not really useful
> > on anything but a tablet that we currently select, like USB_KEYBOARD
> 
> There are also the cases where the OTG controller is routed to a USB
> host port. These are likely set top boxes. It would probably be better
> to have the user be able to explicitly set it to gadget mode if they
> want to do development, but otherwise be in host mode by default.

I don't know, maybe I'm heavily (confirmation) biased, but I've seen
far more people using the micro USB as a gadget (or at least, not as a
host, just powering the board), than people using it as hosts.

Actually, apart from the boards that are wiring it to an USB-A
connector, I haven't seen anyone use that kind of setup, ever.

For the tablets where it's your only option to interact with the
device since you don't have any UARTs, it makes sense. Same thing for
the ones that wire it to a USB-A connector. But for all the boards out
there with a micro or mini USB connector that can power them, I really
feel like the default should be to a gadget.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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