Hi Felipe,
have you had a chance to look at this problem in omap2430_mbus_set_vbus yet?
Are you the person responsible?
thanks,
NeilBrown
On Mon, 9 Jul 2012 01:32:33 -0700 Tony Lindgren <tony@xxxxxxxxxxx> wrote:
> * NeilBrown <neilb@xxxxxxx> [120706 15:44]:
> >
> > Hello `./scripts/get_maintainer.pl -f drivers/usb/musb/omap2430.c`
> >
> > omap2430_musb_set_vbus in omap2430.c contains:
> >
> > while (musb_readb(musb->mregs, MUSB_DEVCTL) & 0x80) {
> >
> > cpu_relax();
> >
> > if (time_after(jiffies, timeout)) {
> > dev_err(musb->controller,
> > "configured as A device timeout");
> > ret = -EINVAL;
> > break;
> > }
> > }
> >
> > having set
> > unsigned long timeout = jiffies + msecs_to_jiffies(1000);
> >
> > so it can busy-loop for up to 1 second. Probably not ideal, but if it works
> > I wouldn't complain.
> >
> > The
> > if (int_usb & MUSB_INTR_SESSREQ) {
> > branch of musb_stage0_irq() called from musb_interrupt (from
> > generic_interrupt) calls this:
> >
> > if (musb->int_usb)
> > retval |= musb_stage0_irq(musb, musb->int_usb,
> > devctl, power);
> >
> > so the busy loop can happen in an interrupt handler (not a threaded interrupt
> > handler), which is probably less ideal.
> >
> > However this can be called with interrupt disabled, as happens at least
> > during resume when resume_irqs() calls:
> >
> > raw_spin_lock_irqsave(&desc->lock, flags);
> > __enable_irq(desc, irq, true);
> > raw_spin_unlock_irqrestore(&desc->lock, flags);
> >
> > and an interrupt is found to be IRQS_PENDING.
> >
> > In this case interrupts are disabled so 'jiffies' never changes so this loop
> > can continue forever.
> >
> > This happens on my (GTA04) phone fairly regularly - between 1 in 10 and 1 in
> > 30 resumes. The musb-hdrc interrupt is pending and reports
> >
> > [ 4957.624176] musb-hdrc musb-hdrc: ** IRQ peripheral usb0040 tx0000 rx0000
> >
> > 'usb0040' is MUSB_INTR_SESSREQ. I think this is triggered by detecting a
> > voltage change on the USB ID pin - is that right? A short-to-earth would be
> > a request to switch to host mode, which is why it tries to enable VBUS.
> > Maybe there is some electrical noise which is being picked up?
>
> I guess that could happen if the transceiver pins are floating during suspend?
>
> > In any case I get the interrupt despite nothing being plugged in, and the 0x80
> > bit of MUSB_DEVCTL never gets cleared.
>
> As far as I remember, musb tries to be smart about changing to host mode,
> and tries to do the session and vbus detection on it's own.. AFAIK, there's
> nothing you can do until musb is done and detects the VBUS is not rising and
> gives up. There are all kind of interrupt flag combinations trying to deal
> with that mess, maybe you need to add yet another one?
>
> > I've added a simple loop counter which aborts the loop after 1000 loops -
> > this takes about 5 seconds, but includes some printks which probably slow it
> > down.
> >
> > In 2 out of 2 cases, subsequent messages show that the hsmmc driver for the
> > uSD card that holds my root filesystem is messed up. It seems to be waiting
> > for a request that is never going to complete.
> > So maybe the hsmmc is causing the noise that triggers the musb issue.
> >
> > I can send a patch which add a loop count if you like, but I suspect you can
> > come up with a much better approach.
>
> Sounds like that loop should be fixed.
>
> Regards,
>
> Tony
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