i.MX6 USB OTG support is broken on linux-next

[Peter Chen]

> 
> On Sat, May 10, 2014 at 07:10:05PM +0800, Peter Chen wrote:
> > On Fri, May 09, 2014 at 09:00:47PM +0800, Shawn Guo wrote:
> > > I'm running next-20140508 kernel on imx6q-sabresd board with USB
> > > mouse/keyboard connected to OTG port.  It  works well on 3.15-rc but
> > > is broken on recent linux-next kernel with the message like below.
> > >
> > > ...
> > > usb 1-1: device v413c p2107 is not supported
> > > hub 1-0:1.0: unable to enumerate USB device on port 1
> > >
> > > With the help from Peter, I found that the issue shows up only when
> > > CONFIG_USB_OTG_FSM is enabled.  The option is enabled by commit
> 8fd2f1f
> > > (ARM: imx_v6_v7_defconfig: Enable drivers for i.MX51 USB Host
> support.)
> > > from IMX tree.
> > >
> > > I guess this is a sign that chipidea otg_fsm driver is buggy?  I do
> not
> > > think dropping CONFIG_USB_OTG_FSM selection from imx_v6_v7_defconfig
> is
> > > a solution, and we need to fix the issue in usb driver, right?
> > >
> >
> > No, Shawn. The solution of this problem is drop CONFIG_USB_OTG_FSM, I
> > guess Denis added it wrongly.
> >
> > According to Embedded Hosts & OTG spec, OTG devices and Embedded Hosts
> > both have Targeted Host functionality, and each Targeted Host has
> > its TPL (Targeted Peripheral List), only the devices are at TPL
> > are supported by Targeted Host.
> >
> > Current Linux TPL only contains limited devices, each Targeted Host
> > needs to update its TPL when it makes product, (The comments at
> > otg_whitelist.h also mention it), and the devices are not at TPL
> > will not be supported, and will report to user as "an unsupported
> > device" error, at current Linux configuration, once the
> CONFIG_USB_OTG_FSM
> > and CONFIG_USB_OTG are chosen, the host will be Targeted Host.
> >
> > The reason why Shawn met this problem is: the imx_v6_v7_defconfig set
> > CONFIG_USB_OTG_FSM, so the CONFIG_USB_OTG and CONFIG_USB_OTG_WHITELIST
> > are set according to dependency, it makes imx6 device as Targeted Host,
> > but the devices connected at Shawn's board are not at TPL, so they are
> > not be supported.
> >
> > In a word the CONFIG_USB_OTG_FSM should not be chosen for
> > defauly kernel configuration. The CONFIG_USB_OTG_FSM should only be
> chosen
> > by default when this device goes to make product and the TPL is updated
> > accordingly.
> 
> Thanks for the explanation, Peter.
> 
> So this is what I see from USB Kconfig.
> 
> config USB_OTG_FSM
>         tristate "USB 2.0 OTG FSM implementation"
>         depends on USB
>         select USB_OTG
>         select USB_PHY
> 
> config USB_OTG_WHITELIST
>         bool "Rely on OTG Targeted Peripherals List"
>         depends on USB_OTG || EXPERT
>         default y if USB_OTG
> 
> I see that USB_OTG_FSM has a dependency on USB_OTG, and
> USB_OTG_WHITELIST depends on USB_OTG, but USB_OTG does *not* depends
> on USB_OTG_WHITELIST.
> 
> I'm not sure why we have 'default y if USB_OTG' for USB_OTG_WHITELIST,
> when this option only makes sense for product producers per your
> explanation.  So maybe dropping the 'default y' is the right fix?
> 

As I explained before: 
"OTG devices and Embedded Hosts both have Targeted Host functionality,
and each Targeted Host has its TPL (Targeted Peripheral List), only the 
devices are at TPL are supported by Targeted Host."

So when the board is OTG & EH (CONFIG_USB_OTG is set), it should
have TPL according to spec. In fact, even the CONFIG_USB_OTG_WHITELIST
is not set, the non-TPL devices have not worked well, eg, it will
not be enumerated again after it has disconnected from host 10 seconds
later due to vbus has turned off by host.

Peter

> diff --git a/drivers/usb/core/Kconfig b/drivers/usb/core/Kconfig
> index cb8e991..9081757 100644
> --- a/drivers/usb/core/Kconfig
> +++ b/drivers/usb/core/Kconfig
> @@ -65,7 +65,6 @@ config USB_OTG
>  config USB_OTG_WHITELIST
>         bool "Rely on OTG Targeted Peripherals List"
>         depends on USB_OTG || EXPERT
> -       default y if USB_OTG
>         help
>           If you say Y here, the "otg_whitelist.h" file will be used as a
>           product whitelist, so USB peripherals not listed there will be
> 
> Shawn