Hi,
On Thu, Feb 26, 2015 at 11:20:29AM -0600, Bin Liu wrote:
> >> > >> > There was already a proper place where we were
> >> > >> > checking for babble interrupts, move babble
> >> > >> > recovery there.
> >> > >> >
> >> > >> > Signed-off-by: Felipe Balbi <ba...@ti.com>
> >> > >> > ---
> >> > >> > drivers/usb/musb/musb_core.c | 13 ++++++-------
> >> > >> > 1 file changed, 6 insertions(+), 7 deletions(-)
> >> > >> >
> >> > >> > diff --git a/drivers/usb/musb/musb_core.c
> >> > >> > b/drivers/usb/musb/musb_core.c
> >> > >> > index 2767ce1bf016..0569b24719e6 100644
> >> > >> > --- a/drivers/usb/musb/musb_core.c
> >> > >> > +++ b/drivers/usb/musb/musb_core.c
> >> > >> > @@ -892,6 +892,12 @@ b_host:
> >> > >> > } else {
> >> > >> > ERR("Stopping host session --
> >> > >> > babble\n");
> >> > >> > musb_writeb(musb->mregs,
> >> > >> > MUSB_DEVCTL, 0);
> >> > >> > +
> >> > >> > + if (is_host_active(musb)) {
> >> > >> > + musb_generic_disable(musb);
> >> > >> > +
> >> > >> > schedule_delayed_work(&musb->recover_work,
> >> > >> > +
> >> > >> > msecs_to_jiffies(100));
> >> > >> > + }
> >> > >>
> >> > >> This change breaks babble recovery, because the following lines above
> >> > >> here
> >> > >>
> >> > >> 873 if (devctl & (MUSB_DEVCTL_FSDEV |
> >> > >> MUSB_DEVCTL_LSDEV)) {
> >> > >> 874 dev_dbg(musb->controller, "BABBLE
> >> > >> devctl: %02x\n", devctl);
> >> > >>
> >> > >> have a bug - DEVCTL_FSDEV bit will be set for high-speed too, so this
> >> > >> 'if' traps babble handling for all cases, never hit on 'else'.
> >> > >
> >> > > We might as well drop that check altogether. Let me see what happens
> >> > > here.
> >> >
> >> > It is good to clean it up, but I guess the babble storm you see is
> >> > caused by something else. I debugged the storm last year in an older
> >> > kernel, it was due to the babble recovery routine does not maintain a
> >> > bit in MUSB_BABBLE_CTL, though I forgot the details now. I am looking
> >> > at this part in the upstream kernel right now.
>
> I am unable to recall why this bug causes the storm, but here is the
> bug fix - SW_SESSION_CTRL bit gets cleared after reset. Please let me
> know if I need to send an seperate patch email.please send it as a patch, but please rebase on top of my testing/next. I've just pushed quite a few patches fixing a bunch of weird inconsistencies with babble recovery. Basically, even though we set SW_SESSION_CONTROL, we were still writing 0 to devctl which was dropping the session anyway! -- balbi
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