On Thu, May 11, 2017 at 01:23:06PM -0700, Tony Lindgren wrote: > * Bin Liu <b-liu@xxxxxx> [170511 13:05]: > > On Thu, May 11, 2017 at 12:38:11PM -0700, Tony Lindgren wrote: > > > > > > I wonder if just keeping VBUS on longer in OTG_STATE_A_WAIT_BCON > > > solves this issue? > > > > We don't cut VBUS intentionally for host mode (when devctl=0x19). The > > VBUS got cut in this case only because when a device is detached, the > > otg state changes from A_HOST -> A_WAIT_BCON, then otg_timer() cuts VBUS > > and sets the state to A_IDLE, then next otg_timer() turns on VBUS (I > > haven't check how the otg state becomes A_WAIT_VRISE from here). > > > > Not sure how to *easily* keep VBUS here, without adding condition check > > in otg_timer() for TG_STATE_A_WAIT_BCON. > > > > > solves this issue? It seems the issue is with modems that get > > > reconfigured after the initial enumeration? > > > > Idealy we shouldn't cut VBUS at all in this case for host-only. I am > > looking for a small patch to solve this, if possilbe ;) > > Maybe try something like below, compile tested only. I don't > think I have any USB modem here to test with. The patch below doesn't help. In device detach by the time dsps_check_status() is called, the otg state is already A_WAIT_BCON, set by musb_root_disconnect() in musb_stage0_irq() when handling DISCONNECT interrupt. > > > > We could poll for new devices every 2 seconds, if anything is seen > > > on the bus, keep VBUS on at least 20 seconds, then if nothing is > > > found, poll every 2 seconds again. > > > > I am not sure this is relevant, VBUS is constantly on once the otg stage > > becomes A_HOST -> A_WAIT_BCON -> A_IDLE -> A_WAIT_VRISE, within a > > second. > > Yup, but it sounds like once the modem changes mode, it disappears > from the USB bus for a long enough time where we go to A_WAIT_BCON > again. Or else I'm misunderstanding what's going on. I don't think it is about how long the modem disappears. When detach happens, DISCONNECT interrupt happens, then dsps_check_status() is scheduled with state A_WAIT_BCON, then VBUS got cut. BTY, I didn't debug with a modem, just with a device detach. Tring to see how to not cut vbus at all in dsps_check_status(). > > It's also possible that we have dsps_check_status() getting called > again on disconnect before the new 20 second period is over, I did > not check for that yet. After a few trials, I start to think about a little cleanup in the otg state machine in the musb drivers, I think we need to somehow distinguish between normal and error conditions for A_WAIT_BCON state. Regards, -Bin. > > Regards, > > Tony > > 8< ----------------------- > diff --git a/drivers/usb/musb/musb_dsps.c b/drivers/usb/musb/musb_dsps.c > --- a/drivers/usb/musb/musb_dsps.c > +++ b/drivers/usb/musb/musb_dsps.c > @@ -270,6 +270,10 @@ static int dsps_check_status(struct musb *musb, void *unused) > musb_writel(musb->ctrl_base, wrp->coreintr_set, > MUSB_INTR_VBUSERROR << wrp->usb_shift); > break; > + case OTG_STATE_A_HOST: > + if (glue->vbus_irq) > + dsps_mod_timer(glue, 20000); /* 20s */ > + break; > default: > break; > } > -- > 2.13.0 -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
