* 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. > > 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. 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. 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-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
