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 15:44:39 +0200
From:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:	Bin Liu <binmlist@...il.com>
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

On 08/13/2013 03:33 PM, Bin Liu wrote:
> Sebastian,

Hi Bin,

>> 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.

This was a misunderstanding then. Sorry. I understood that the bin has
to be unset and then the controller set it once a device there.

> 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.
evm is the only I am aware of. The evm-sk and beagle bone have just one
port. Beagle bone black is not mainline.

>> 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...)

This is the case already. From musb_start()
…
        if (musb->port_mode != MUSB_PORT_MODE_HOST &&
             (devctl & MUSB_DEVCTL_VBUS) == MUSB_DEVCTL_VBUS) {
                 musb->is_active = 1;
         } else {
                 devctl |= MUSB_DEVCTL_SESSION;
         }
…

>>> -Bin.

Sebastian
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