Re: [RFC] usb: musb: dsps, OTG detection

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On Mon, Oct 14, 2013 at 10:22 AM, Markus Pargmann <mpa@xxxxxxxxxxxxxx> wrote:
> Hi,
>
> On Mon, Oct 14, 2013 at 08:54:09AM -0500, Bin Liu wrote:
>> On Mon, Oct 14, 2013 at 8:35 AM, Markus Pargmann <mpa@xxxxxxxxxxxxxx> wrote:
>> > The USB Controller does not support ID pin change interrupts. So we have
>> > to use a polling function to detect changes of A/B device state
>> > (otg_timer). This poll function has to check in several states if a
>> > other device type might be connected to the USB port. This check is
>> > triggered by manually starting/stopping a USB Session.
>>
>> I think this is an arguable approach. Toggling the SESSION in
>> otg_timer() causes voltage pulses on VBUS, which will not pass the USB
>> certification.
>
> This is only done when no device is connected, so I am not sure if it is
> important. Unfortunately we do not see the A/B state changes until

That is right, and I don't think it hurts. The only problem is that
the USB certification test sees the VBUS pulses and fails.

> toggling the SESSION. Is there another way to check this?

Unfortunately, toggling SESSION in b_idle is the only way I am aware of.

>
>>
>> I have not seen any products required the dynamic dual role switching
>> yet. It always fixed in either device mode or host mode.
>
> OTG is explicitly listed in the devicetree bindings documentation, so
> I think the driver should be able to detect different roles.

Yes, MUSB supports OTG. But I have not seen anyone use OTG yet, and I
not sure if it is a good idea to add the OTG support, but fail the usb
certification test.

Regards,
-Bin.

>
> Regards,
>
> Markus Pargmann
>
>>
>> Regards,
>> -Bin.
>>
>> >
>> > So in A mode, we cancel the currently running session which also
>> > disables the possibility to detect new devices via interrupt. In B mode,
>> > we start a session to check for ID-Pin and possibly connected devices.
>> >
>> > Whenever a real USB session ends, we have to trigger the otg_timer poll
>> > function again.
>> >
>> > Signed-off-by: Markus Pargmann <mpa@xxxxxxxxxxxxxx>
>> > ---
>> >  drivers/usb/musb/musb_dsps.c | 84 ++++++++++++++++++++++++++++++++++++++++----
>> >  1 file changed, 78 insertions(+), 6 deletions(-)
>> >
>> > diff --git a/drivers/usb/musb/musb_dsps.c b/drivers/usb/musb/musb_dsps.c
>> > index b24b697..0245e8d 100644
>> > --- a/drivers/usb/musb/musb_dsps.c
>> > +++ b/drivers/usb/musb/musb_dsps.c
>> > @@ -178,6 +178,43 @@ static const struct file_operations musb_regdump_fops = {
>> >
>> >  #endif /* IS_ENABLED(CONFIG_DEBUG_FS) */
>> >
>> > +/*
>> > + * Compare driver and hardware mode and update driver state if necessary.
>> > + * Not all hardware changes actually reach the driver through interrupts.
>> > + */
>> > +static void dsps_update_mode(struct musb *musb)
>> > +{
>> > +       u8 devctl;
>> > +
>> > +       devctl = dsps_readb(musb->mregs, MUSB_DEVCTL);
>> > +
>> > +       switch (musb->xceiv->state) {
>> > +       case OTG_STATE_A_IDLE:
>> > +               if (devctl & MUSB_DEVCTL_BDEVICE) {
>> > +                       dev_dbg(musb->controller, "detected controller state B, software state A\n");
>> > +                       musb->xceiv->state = OTG_STATE_B_IDLE;
>> > +               }
>> > +               break;
>> > +       case OTG_STATE_B_IDLE:
>> > +               if (!(devctl & MUSB_DEVCTL_BDEVICE)) {
>> > +                       dev_dbg(musb->controller, "detected controller state A, software state B\n");
>> > +                       musb->xceiv->state = OTG_STATE_A_IDLE;
>> > +               }
>> > +               break;
>> > +       default:
>> > +               if (!(devctl & MUSB_DEVCTL_SESSION)) {
>> > +                       dev_dbg(musb->controller, "detected controller out of session (%x), software state %s\n",
>> > +                               devctl,
>> > +                               usb_otg_state_string(musb->xceiv->state));
>> > +                       if (devctl & MUSB_DEVCTL_BDEVICE)
>> > +                               musb->xceiv->state = OTG_STATE_B_IDLE;
>> > +                       else
>> > +                               musb->xceiv->state = OTG_STATE_A_IDLE;
>> > +               }
>> > +               break;
>> > +       }
>> > +}
>> > +
>> >  /**
>> >   * dsps_musb_enable - enable interrupts
>> >   */
>> > @@ -229,6 +266,8 @@ static void otg_timer(unsigned long _musb)
>> >         u8 devctl;
>> >         unsigned long flags;
>> >
>> > +       dsps_update_mode(musb);
>> > +
>> >         /*
>> >          * We poll because DSPS IP's won't expose several OTG-critical
>> >          * status change events (from the transceiver) otherwise.
>> > @@ -239,6 +278,16 @@ static void otg_timer(unsigned long _musb)
>> >
>> >         spin_lock_irqsave(&musb->lock, flags);
>> >         switch (musb->xceiv->state) {
>> > +       case OTG_STATE_A_IDLE:
>> > +       case OTG_STATE_A_WAIT_VRISE:
>> > +               /*
>> > +                * Poll the devctl register to know when the controller switches
>> > +                * back to B state.
>> > +                */
>> > +               musb_writeb(mregs, MUSB_DEVCTL,
>> > +                               devctl & (~MUSB_DEVCTL_SESSION));
>> > +               mod_timer(&glue->timer, jiffies + wrp->poll_seconds * HZ);
>> > +               break;
>> >         case OTG_STATE_A_WAIT_BCON:
>> >                 devctl &= ~MUSB_DEVCTL_SESSION;
>> >                 dsps_writeb(musb->mregs, MUSB_DEVCTL, devctl);
>> > @@ -251,6 +300,8 @@ static void otg_timer(unsigned long _musb)
>> >                         musb->xceiv->state = OTG_STATE_A_IDLE;
>> >                         MUSB_HST_MODE(musb);
>> >                 }
>> > +               mod_timer(&glue->timer,
>> > +                               jiffies + wrp->poll_seconds * HZ);
>> >                 break;
>> >         case OTG_STATE_A_WAIT_VFALL:
>> >                 musb->xceiv->state = OTG_STATE_A_WAIT_VRISE;
>> > @@ -258,12 +309,24 @@ static void otg_timer(unsigned long _musb)
>> >                             MUSB_INTR_VBUSERROR << wrp->usb_shift);
>> >                 break;
>> >         case OTG_STATE_B_IDLE:
>> > +               /*
>> > +                * There's no ID-changed IRQ, so we have no good way to tell
>> > +                * when to switch to the A-Default state machine (by setting
>> > +                * the DEVCTL.Session bit).
>> > +                *
>> > +                * Workaround:  whenever we're in B_IDLE, try setting the
>> > +                * session flag every few seconds.  If it works, ID was
>> > +                * grounded and we're now in the A-Default state machine.
>> > +                *
>> > +                * NOTE: setting the session flag is _supposed_ to trigger
>> > +                * SRP but clearly it doesn't.
>> > +                */
>> > +               musb_writeb(mregs, MUSB_DEVCTL, devctl | MUSB_DEVCTL_SESSION);
>> >                 devctl = dsps_readb(mregs, MUSB_DEVCTL);
>> > -               if (devctl & MUSB_DEVCTL_BDEVICE)
>> > -                       mod_timer(&glue->timer,
>> > -                                       jiffies + wrp->poll_seconds * HZ);
>> > -               else
>> > +               if (!(devctl & MUSB_DEVCTL_BDEVICE))
>> >                         musb->xceiv->state = OTG_STATE_A_IDLE;
>> > +               mod_timer(&glue->timer,
>> > +                               jiffies + wrp->poll_seconds * HZ);
>> >                 break;
>> >         default:
>> >                 break;
>> > @@ -376,7 +439,6 @@ static irqreturn_t dsps_interrupt(int irq, void *hci)
>> >                         MUSB_HST_MODE(musb);
>> >                         musb->xceiv->otg->default_a = 1;
>> >                         musb->xceiv->state = OTG_STATE_A_WAIT_VRISE;
>> > -                       del_timer(&glue->timer);
>> >                 } else {
>> >                         musb->is_active = 0;
>> >                         MUSB_DEV_MODE(musb);
>> > @@ -397,8 +459,16 @@ static irqreturn_t dsps_interrupt(int irq, void *hci)
>> >                 ret |= musb_interrupt(musb);
>> >
>> >         /* Poll for ID change */
>> > -       if (musb->xceiv->state == OTG_STATE_B_IDLE)
>> > +       switch (musb->xceiv->state) {
>> > +       case OTG_STATE_A_IDLE:
>> > +       case OTG_STATE_A_WAIT_BCON:
>> > +       case OTG_STATE_A_WAIT_VRISE:
>> > +       case OTG_STATE_B_IDLE:
>> >                 mod_timer(&glue->timer, jiffies + wrp->poll_seconds * HZ);
>> > +               break;
>> > +       default:
>> > +               break;
>> > +       }
>> >  out:
>> >         spin_unlock_irqrestore(&musb->lock, flags);
>> >
>> > @@ -479,6 +549,8 @@ static int dsps_musb_init(struct musb *musb)
>> >
>> >         dev_info(dev, "%s:%d %s: OK\n", __FILE__, __LINE__, __func__);
>> >
>> > +       musb->xceiv->otg->default_a = 0;
>> > +
>> >         return 0;
>> >  }
>> >
>> > --
>> > 1.8.4.rc3
>> >
>> > --
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>>
>
> --
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