netdev - RE: imx7: USB modem reset causes modem to not re-connect

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Date:   Tue, 13 Dec 2022 11:17:41 +0000
From:   Jun Li <jun.li@....com>
To:     Fabio Estevam <festevam@...il.com>
CC:     "bjorn@...k.no" <bjorn@...k.no>,
        Peter Chen <peter.chen@...nel.org>,
        Marek Vasut <marex@...x.de>, netdev <netdev@...r.kernel.org>,
        USB list <linux-usb@...r.kernel.org>,
        Alexander Stein <alexander.stein@...tq-group.com>,
        Schrempf Frieder <frieder.schrempf@...tron.de>
Subject: RE: imx7: USB modem reset causes modem to not re-connect



> -----Original Message-----
> From: Fabio Estevam <festevam@...il.com>
> Sent: Tuesday, December 13, 2022 5:33 PM
> To: Jun Li <jun.li@....com>
> Cc: bjorn@...k.no; Peter Chen <peter.chen@...nel.org>; Marek Vasut
> <marex@...x.de>; netdev <netdev@...r.kernel.org>; USB list
> <linux-usb@...r.kernel.org>; Alexander Stein
> <alexander.stein@...tq-group.com>; Schrempf Frieder
> <frieder.schrempf@...tron.de>
> Subject: Re: imx7: USB modem reset causes modem to not re-connect
> 
> Hi Li Jun,
> 
> On Tue, Dec 13, 2022 at 5:15 AM Jun Li <jun.li@....com> wrote:
> 
> > So this disconnect and then connect is you expected behavior?
> 
> Yes, correct.
> 
> I found a way to get this behavior in both 5.10 as well as 6.1 kernels:
> If I remove the USB_OTG2_OC pinctrl entry and pass 'disable-over-current',
> it works as expected.

So the pinctrl is using MX7D_PAD_UART3_RTS_B__USB_OTG2_OC?

> 
> On this board, the MX7D_PAD_UART3_RTS_B__USB_OTG2_OC pad goes to 3.3V via
> a 10Kohm pullup resistor.

So the pad is fixed at 3.3V, never can be tied low?

> 
> Could you please explain why removing theUSB_OTG2_OC entry makes things to
> work?

So the actual board design does not want to have OC feature, right? if that
is the case, disable-over-current is the right way.

What's the OC polarity config in your SW, active low, or active high?
Basically if the OC condition is active, the host mode cannot work
well.

Li Jun
> 
> Thanks