[RFC] usb: musb: dsps, OTG detection
Bin Liu
binmlist at gmail.com
Mon Oct 14 16:43:35 EDT 2013
On Mon, Oct 14, 2013 at 10:22 AM, Markus Pargmann <mpa at pengutronix.de> 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 at pengutronix.de> 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 at pengutronix.de>
>> > ---
>> > 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
>> >
>> > --
>> > To unsubscribe from this list: send the line "unsubscribe linux-usb" in
>> > the body of a message to majordomo at vger.kernel.org
>> > More majordomo info at http://vger.kernel.org/majordomo-info.html
>>
>
> --
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