linux-kernel - Re: [PATCH v3 0/5] Add support for SW babble Control

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Date:	Tue, 13 May 2014 13:37:00 -0500
From:	Bin Liu <binmlist@...il.com>
To:	George Cherian <george.cherian@...com>
Cc:	Daniel Mack <zonque@...il.com>, linux-kernel@...r.kernel.org,
	linux-usb@...r.kernel.org, linux-omap@...r.kernel.org,
	balbi@...com, gregkh@...uxfoundation.org
Subject: Re: [PATCH v3 0/5] Add support for SW babble Control

Hi,

On Tue, May 13, 2014 at 8:24 AM, George Cherian <george.cherian@...com> wrote:
> Hi Daniel,
>
>
> On 5/13/2014 6:44 PM, Daniel Mack wrote:
>>
>> Hi George,
>>
>> On 05/13/2014 02:57 PM, George Cherian wrote:
>>>
>>> I never enabled the MUSB_BABBLE_SW_SESSION_CTRL in the MUSB_BABBLE_CTL
>>> reg.
>>> can you try with the following patch.
>>>
>>> diff --git a/drivers/usb/musb/musb_dsps.c b/drivers/usb/musb/musb_dsps.c
>>> index 1ae6681..1160cd1 100644
>>> --- a/drivers/usb/musb/musb_dsps.c
>>> +++ b/drivers/usb/musb/musb_dsps.c
>>> @@ -477,8 +477,11 @@ static int dsps_musb_init(struct musb *musb)
>>>          * logic enabled.
>>>          */
>>>         val = dsps_readb(musb->mregs, MUSB_BABBLE_CTL);
>>> -       if (val == MUSB_BABBLE_RCV_DISABLE)
>>> +       if (val == MUSB_BABBLE_RCV_DISABLE) {
>>>                 glue->sw_babble_enabled = true;
>>> +               val |= MUSB_BABBLE_SW_SESSION_CTRL;
>>> +               dsps_writeb(musb->mregs, MUSB_BABBLE_CTL, val);
>>> +       }
>>>         ret = dsps_musb_dbg_init(musb, glue);
>>>         if (ret)
>>
>> MUSB_BABBLE_STUCK_J still remains unset, so I get the same result as
>> without the patch: a full glue reset is conducted. Do I get you right
>> that you expect MUSB_BABBLE_STUCK_J to be set in babble conditions when
>> MUSB_BABBLE_SW_SESSION_CTRL is set?
>>
> Basically, there are 2 types of babble conditions.
> 1) Transient babble condition - which could be recovered from without an IP
> reset .
> 2) Babble condition - which could be recovered from only by doing an IP
> reset.
>
> Looks like you are always hitting case 2 (Most times am also hitting the
> same).
> Case 1 is really hard to reproduce. I don't have a reliable method as of now
> to
> reproduce this case consistently.
>
>> [   19.672373] CAUTION: musb: Babble Interrupt Occurred
>> [   19.677776] musb_stage0_irq 789: unhandled DISCONNECT transition
>> (a_wait_bcon)
>> [   19.685815] usb 1-1: USB disconnect, device number 3
>> [   19.769720] musb-hdrc musb-hdrc.0.auto: babble: MUSB_BABBLE_CTL value
>> 44
>> [   19.776765] musb-hdrc musb-hdrc.0.auto: STUCK_J is reset
>>
>>
>> I don't quite follow, especially as I lack documentation of the IP core.
>> How do you test babble errors, is there any way to force them to happen
>> reliably?
>
>
> There is no 100% reliable method to force it to happen. Following is

I have a way to force babble happen reliably - shorting DP or DM to
VBUS. I opened the far-end plug of the USB cable, so I can easily
short DP or DM to VBUS.

But the interesting thing is that with TI 3.2 kernel, shorting DP or
DM to VBUS causes MISC register to be 0x4, but the result is
completely opposite in TI 3.12.10 kernel, which cause MISC to be 0x64.

So in the 3.2 kernel, the babble handing resets the controller, but
the 3.12.10 does not.

Regards,
-Bin.

> my setup ,
> I have a HUB with 4 devices connected , which gives me a Babble interrupt
> on both connects and disconnects ( Not always though).
>
>> Anyway, the full glue layer solves this rare condition quite well for
>> me. Is there any downside of this?
>>
>>
>> Daniel
>>
>
>
> --
> -George
>
> --
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