linux-kernel - Re: [PATCH v4 1/6] usb: musb: core: Handle Babble condition only in HOST mode

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Date:	Tue, 20 May 2014 10:02:47 +0530
From:	George Cherian <george.cherian@...com>
To:	Bin Liu <binmlist@...il.com>
CC:	<linux-kernel@...r.kernel.org>, <linux-usb@...r.kernel.org>,
	<linux-omap@...r.kernel.org>, <gregkh@...uxfoundation.org>,
	<balbi@...com>, <zonque@...il.com>, <b-liu@...com>
Subject: Re: [PATCH v4 1/6] usb: musb: core: Handle Babble condition only
 in HOST mode

Hi Bin,
On 5/19/2014 9:24 PM, Bin Liu wrote:
> Hi,
>
> On Mon, May 19, 2014 at 8:39 AM, George Cherian <george.cherian@...com> wrote:
>> BABBLE and RESET share the same interrupt. The interrupt
>> is considered to be RESET if MUSB is in peripheral mode and
>> as a BABBLE if MUSB is in HOST mode.
>>
>> Handle babble condition iff MUSB is in HOST mode.
>>
>> Signed-off-by: George Cherian <george.cherian@...com>
>> ---
>>   drivers/usb/musb/musb_core.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/usb/musb/musb_core.c b/drivers/usb/musb/musb_core.c
>> index 61da471..eff3c5c 100644
>> --- a/drivers/usb/musb/musb_core.c
>> +++ b/drivers/usb/musb/musb_core.c
>> @@ -849,7 +849,7 @@ b_host:
>>          }
>>
>>          /* handle babble condition */
>> -       if (int_usb & MUSB_INTR_BABBLE)
>> +       if (int_usb & MUSB_INTR_BABBLE && is_host_active(musb))
>>                  schedule_work(&musb->recover_work);
> I guess my following comments are for Daniel's patch as while which
> initially added the babble work.
>
> Should this if statement be merged into the previous 'if(int_usb &
> MUSB_INTR_RESET)' one, which handles the same interrupt and already
> handles host and device mode respectively.

Initially I too had the babble handling as part of  'if(int_usb & 
MUSB_INTR_RESET)'
one. But during my tests I hit a corner case where in we hit a BABBLE 
condition
on disconnect. In such case the babble interrupt can be handled only if 
we have a seperate
check, else its considered as a BUS RESET.

When all devices are disconnected  MUSB_DEVCTL_HM = 0 and the code 
always enter the
else path. In this path it treats the BABBLE as a BUS RESET.

> Regards,
> -Bin.
>
>>   #if 0
>> --
>> 1.8.3.1
>>
>> --
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-- 
-George

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