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

[Laurent Pinchart <laurent.pinchart-ryLnwIuWjnjg/C1BVhZhaw@public.gmane.org>]

Hello,

On Friday 11 Nov 2016 08:53:22 Tony Lindgren wrote:
> * Bin Liu <b-liu-l0cyMroinI0@public.gmane.org> [161111 08:25]:
> > 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.

Which board is that ? For the problem to occur the board has to have an OTG 
connector.

> >> 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.

MUSB_DEVCTL is first set to 0 by musb_generic_disable() called from 
musb_init_controller(). The register is then left untouched (as far as I can 
tell, I've intercepted all musb_writeb() and musb_readb() calls) until 
musb_start() to reads the register. The read value has BDEVICE and VBUS=3 set.

> >> and sets musb->is_active to 1. Later, musb_bus_suspend() complains
> >> because is_active is not 0.
> >> 
> >> What is wrong in that sequence ?
> 
> I think the issue is pandaboard connected to a PC with mini-B
> cable while musb is being forced to host mode?

The issue also occurs when the cable isn't connected.

-- 
Regards,

Laurent Pinchart

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