Re: [PATCH 2/3] omap3isp: Disable CCDC's VD0 and VD1 interrupts when stream is not enabled

[Tim Nordell <tim.nordell@logicpd.com>]

Laurent -

On 03/18/15 10:19, Laurent Pinchart wrote:
> Hi Tim,
>
> Thank you for the patch.
>
> On Tuesday 10 March 2015 14:24:53 Tim Nordell wrote:
>> During testing there appeared to be a race condition where the IRQs
>> for VD0 and VD1 could be triggered while enabling the CCDC module
>> before the pipeline status was updated.  Simply modify the trigger
>> conditions for VD0 and VD1 so they won't occur when the CCDC module
>> is not enabled.
>>
>> (When this occurred during testing, the VD0 interrupt was occurring
>> over and over again starving the rest of the system.)
> I'm curious, might this be caused by the input (adv7180 in your case) being
> enabled before the ISP ? The CCDC is very sensitive to any glitch in its input
> signals, you need to make sure that the source is disabled before its subdev
> s_stream operation is called. Given that the adv7180 driver doesn't implement
> s_stream, I expect it to be free-running, which is definitely a problem.
>
I'll give that a shot and try add code into the adv7180 driver to turn 
on and off its output signals.  However, it seems like if the driver can 
avoid a problem presented by external hardware (or other drivers), that 
it should.  Something like either turning off the VD0 and VD1 interrupts 
when not in use, or by simply moving the trigger points for those 
interrupts (as I did here) to avoid problems by presented by signals to 
the system is probably a good thing for robustness.

- Tim