linux-kernel - Re: [PATCH 14/16] usb: musb: dsps: add MUSB_DEVCTL

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Date:	Fri, 26 Jul 2013 22:07:14 -0500
From:	Bin Liu <binmlist@...il.com>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	balbi@...com, george.cherian@...com
Subject: Re: [PATCH 14/16] usb: musb: dsps: add MUSB_DEVCTL_SESSION back after removal

Sebastian,

On Fri, Jul 26, 2013 at 3:35 PM, Sebastian Andrzej Siewior
<bigeasy@...utronix.de> wrote:
>> My build server is down this afternoon. Once it comes back next week,
>> I will try 3.8 again, to see how I can help on this USB1 host mode
>> issue. its devctl register should stay on 0x19 even nothing is
>> connected.
>
> Your help is greatly appreciated. To hear what will happen :)
>
> Sebastian

I have not tested it yet, but I believe I found why host mode works on
TI 3.2 kernel but not on mainline. Please look at Line 786 in 3.2
kernel musb_core.c [1].

773         if ((int_usb & MUSB_INTR_DISCONNECT) && !musb->ignore_disconnect) {
......
785                                 if (musb->a_wait_bcon != 0 &&
786                                                 is_otg_enabled(musb))
787                                         musb_platform_try_idle(musb, jiffies
788                                         +
msecs_to_jiffies(musb->a_wait_bcon));

So when the device is unplugged, *_try_idle() is not called in host
mode, then the SESSION bit will stay set. But in mainline kernel,
*_try_idle() will be called regardless.

Please let me know your thoughts.

Regards,
-Bin.

[1] http://arago-project.org/git/projects/?p=linux-am33x.git;a=blob;f=drivers/usb/musb/musb_core.c;h=075aa5f9bec7cd041aa24eb534209fa756ed84fe;hb=refs/heads/v3.2-staging
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