Re: [PATCH 0/4] musb fixes for v4.9-rc cycle

[Bin Liu <b-liu-l0cyMroinI0@public.gmane.org>]

On Fri, Nov 11, 2016 at 01:39:28AM +0200, Laurent Pinchart wrote:
> Hello,
> 
> On Friday 11 Nov 2016 00:27:52 Laurent Pinchart wrote:
> > On Thursday 10 Nov 2016 13:42:34 Tony Lindgren wrote:
> > > * Laurent Pinchart <laurent.pinchart-ryLnwIuWjnjg/C1BVhZhaw@public.gmane.org> [161110 13:29]:
> > >> I had to disable CONFIG_USB_GADGET is compiling it as a module prevents
> > >> selecting CONFIG_NOP_USB_XCEIV=y, which is a dependency for
> > >> CONFIG_USB_EHCI_HCD_OMAP=m.
> > >> 
> > >> The new configuration resulted in a few changes, among which the most
> > >> notable is
> > >> 
> > >> -# CONFIG_USB_MUSB_HOST is not set
> > >> -# CONFIG_USB_MUSB_GADGET is not set
> > >> -CONFIG_USB_MUSB_DUAL_ROLE=y
> > >> +CONFIG_USB_MUSB_HOST=y
> > >> 
> > >> I then get the same error as originally reported.
> > > 
> > > Yeah OK, that's the problem.. We still have musb hardware
> > > trying to do things on it's own and phy trying to detect
> > > the state.
> > > 
> > > Any ideas why we have a dependency like that in Kconfig?
> > 
> > Well, with CONFIG_USB_GADGET disabled, I don't expect CONFIG_USB_MUSB_GADGET
> > to be enabled. MUSB can only operate in host mode in that case, so musb->
> > xceiv->otg->state = OTG_STATE_A_IDLE makes sense.
> 
> I've tried to investigate this but I'm not familiar enough with the MUSB 
> driver to reach any conclusion. Felipe, if you have time could you give me a 
> hand ?
> 
> To summarize the issue, on a pandaboard-es where the MUSB is wired to an OTG 
> connector with mode rightfully set to MUSB_PORT_MODE_DUAL_ROLE in DT, a kernel 
> configured with CONFIG_USB_MUSB_HOST=y (for instance because CONFIG_USB_GADGET 
> is disabled) will print an endless stream of the following meessage.
> 
> [    2.766174] musb_bus_suspend 2586: trying to suspend as a_idle while active

I don't have a omap3/4 platform to test on this, but I don't see this
problem on am335x board.

> 
> musb_init_controller() performs the following actions
> 
>         case MUSB_PORT_MODE_DUAL_ROLE:
>                 status = musb_host_setup(musb, plat->power);
>                 if (status < 0)
>                         goto fail3;
>                 status = musb_gadget_setup(musb);
>                 if (status) {
>                         musb_host_cleanup(musb);
>                         goto fail3;
>                 }
>                 status = musb_platform_set_mode(musb, MUSB_OTG);
>                 break;
> 
> and as gadget support is disabled musb_gadget_setup() compiles to a no-op 
> inline function. The system is thus configured in host mode by 
> musb_host_setup() with musb->xceiv->otg->state = OTG_STATE_A_IDLE. A later 
> call to musb_start() verifies the condition
> 
>         if (musb->port_mode != MUSB_PORT_MODE_HOST &&
>                         musb->xceiv->otg->state != OTG_STATE_A_WAIT_BCON &&
>                         (devctl & MUSB_DEVCTL_VBUS) == MUSB_DEVCTL_VBUS) {

To get there, devctl[MUSB_DEVCTL_VBUS] bits have to be set, where does the
vbus voltage come from? Session is not on yet.

> 
> and sets musb->is_active to 1. Later, musb_bus_suspend() complains because 
> is_active is not 0.
> 
> What is wrong in that sequence ?
> 
> -- 
> Regards,
> 
> Laurent Pinchart
> 

Regards,
-Bin.

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