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.
I have not seen any products required the dynamic dual role switching
yet. It always fixed in either device mode or host mode.
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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