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

[Li Jun]

On Sat, May 10, 2014 at 09:18:36PM +0800, Shawn Guo wrote:
> + Robin and David,
> 
> 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?
> 
> 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
As Peter suggested, do not enable OTG_FSM in defconfig since there are very few
HNP&SRP capable device in market. With OTG_FSM enabled, even USB_OTG_WHITELIST
is not selected, the OTG port still can't work the same as before if you connect
a normal usb device to it.

Li Jun