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

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Date:	Mon, 26 May 2014 14:16:23 +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

On 5/23/2014 2:12 AM, Bin Liu wrote:
> Hi George,
>
> On Mon, May 19, 2014 at 11:32 PM, George Cherian <george.cherian@...com> wrote:
>> 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.
> The code flow is a bit confusing, two if() handle the same interrupt.
> The second one implied using 'handled = IRQ_HANDLED;' from the first
> one.
> Also does the switch() in else{} in the first if() cause any side effect?
No it doesn't.
> Since this babble handing is AM335x specific, how about handle it in
> dsps_interrupt() in musb_dsps.c, which already has an entry for babble
> interrupt? TI 3.2 kernel does this way.
That the reason we have platform specific callbacks added  from the main 
interrupt handler.
> Regards,
> -Bin.
>
>>
>>> Regards,
>>> -Bin.
>>>
>>>>    #if 0
>>>> --
>>>> 1.8.3.1
>>>>
>>>> --
>>>> To unsubscribe from this list: send the line "unsubscribe linux-usb" in
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>>
>>
>> --
>> -George
>>


-- 
-George

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