linux-kernel - Re: [PATCH] usb-musb: keep VBUS on when device is disconnected

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Date:   Mon, 15 May 2017 09:07:10 +0200
From:   Moreno Bartalucci <moreno.bartalucci@...norama.it>
To:     Bin Liu <b-liu@...com>
Cc:     Tony Lindgren <tony@...mide.com>, Lars Melin <larsm17@...il.com>,
        "linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Alessio Igor Bogani <abogani@...nel.org>
Subject: Re: [PATCH] usb-musb: keep VBUS on when device is disconnected


> Il giorno 12 mag 2017, alle ore 17:21, Bin Liu <b-liu@...com> ha scritto:
> 
> […]
> 
> Moreno, would you mind to test the patch below with your modem?
> 
> […]
>> 
>>> 8< --------------------
>>> diff --git a/drivers/usb/musb/musb_dsps.c b/drivers/usb/musb/musb_dsps.c
>>> index 9c7ee26ef388..465281244596 100644
>>> --- a/drivers/usb/musb/musb_dsps.c
>>> +++ b/drivers/usb/musb/musb_dsps.c
>>> @@ -245,9 +245,14 @@ static int dsps_check_status(struct musb *musb, void *unused)
>>>                dsps_mod_timer_optional(glue);
>>>                break;
>>>        case OTG_STATE_A_WAIT_BCON:
>>> +               /* keep VBUS on for host-only mode */
>>> +               if (musb->port_mode == MUSB_PORT_MODE_HOST) {
>>> +                       dsps_mod_timer_optional(glue);
>>> +                       break;
>>> +               }
>>>                musb_writeb(musb->mregs, MUSB_DEVCTL, 0);
>>>                skip_session = 1;
>>> -               /* fall */
>>> +               /* fall through */
>>> 
>>>        case OTG_STATE_A_IDLE:
>>>        case OTG_STATE_B_IDLE:

Hello Bin,

I tested the above patch with my device and it seems to work correctly with the current mainline kernel.

I tested it with my “production” kernel as well (4.9.20) but, for it to work, I had to change it slightly.

This is what I tested for kernel 4.9.20:

--- a/drivers/usb/musb/musb_dsps.c	2017-05-15 08:40:23.000000000 +0200
+++ b/drivers/usb/musb/musb_dsps.c	2017-05-15 08:49:17.000000000 +0200
@@ -213,6 +213,12 @@ static int dsps_check_status(struct musb
 				msecs_to_jiffies(wrp->poll_timeout));
 		break;
 	case OTG_STATE_A_WAIT_BCON:
+		/* keep VBUS on for host-only mode */
+		if (musb->port_mode == MUSB_PORT_MODE_HOST) {
+			mod_timer(&glue->timer, jiffies +
+					msecs_to_jiffies(wrp->poll_timeout));
+			break;
+		}
 		musb_writeb(musb->mregs, MUSB_DEVCTL, 0);
 		skip_session = 1;
 		/* fall */

In this form, it appears to work properly for 4.9.20 too.

Best regards,

Moreno