[v2] USB: chipidea: Do not hang when CONFIG_USB_CHIPIDEA_ULPI is not selected

[Shawn Guo <shawnguo@kernel.org>]

On Mon, Jul 02, 2018 at 11:22:55PM -0300, Fabio Estevam wrote:
> Hi Shawn,
> 
> On Mon, Jul 2, 2018 at 11:06 PM, Shawn Guo <shawnguo@kernel.org> wrote:
> 
> > A second thought on this - shouldn't such dependency be solved by
> > Kconfig select clause?
> 
> I suspect we are not able to fix it via Kconfig as we really don't
> know if a system uses ULPI interface or not via Kconfig perspective.
> 
> If we always select the chipidea ULPI driver, then it will be dead
> code for boards that do not use ULPI.
> 
> Currently there are some defconfigs that explicitly select the
> chipidea ulpi driver:
> 
> arch/arm/configs/qcom_defconfig:CONFIG_USB_CHIPIDEA_ULPI=y
> arch/arm64/configs/defconfig:CONFIG_USB_CHIPIDEA_ULPI=y
> 
> I would be interested to get feedback whether it would be possible to
> fix it on a different way.

We can have the options in defconfig, but they can still be turned off
for whatever reason and we get the hang.  Really, missing a user
selectable option in defconfig shouldn't result in a system hang. 

Shawn
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