linux-kernel - Re: [PATCH] usb: musb: am335x: Do not remove the session bin HOST-only mode

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Date:	Tue, 13 Aug 2013 08:33:34 -0500
From:	Bin Liu <binmlist@...il.com>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	balbi@...com, george.cherian@...com
Subject: Re: [PATCH] usb: musb: am335x: Do not remove the session bin
 HOST-only mode

Sebastian,

On Tue, Aug 13, 2013 at 8:17 AM, Sebastian Andrzej Siewior
<bigeasy@...utronix.de> wrote:
> On 08/13/2013 03:03 PM, Bin Liu wrote:
>> Sebastian,
>
> Hi Bin,
>
>>>>> +    if (musb->port_mode == MUSB_PORT_MODE_HOST) {
>>>>> +        val = USBMODE_IDDIG_A;
>>>>> +        val |= USBMODE_ID_MUX_REG;
>>>>
>> I am going to so some tests today for this. I don't object to use the
>> mode register, but am wondering why we have to play with it for
>> host-only mode. The ID pin is grounded for host-only mode, which
>> should cause the same as setting mode register.
>
> I've been looking at the wiki page and it did not mention the ID pin
> for the second port. If it is grounded then this piece can be removed
I thought you have already tried that without setting the mode
register the session bit cannot stay set.
I am not sure if anywhere mentioned about the ID pin, but ASAIK all
the different boards using am335x have ID pin grounded for host port.

> and the magic trick is just to skip the try_idle() call.
Agreed.

>
> I haven't found anything saying that it is required to clear the
> session bin in host mode, only in OTG. And then, I would assume to
Agreed.

> receive a session interrupt once we have the proper VBUS level which
> does not happen.
The TI 3.2 kernel for am335x sets the session bit in musb_start() for
host-only mode. Maybe we can do something similar in here? (I noticed
mush_start() has gone in mainline, but have not got a chance to check
the details...)

>
>> -Bin.
>
> Sebastian
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