Memory corruption using CSI

[mod42]

We have a custom board which uses a custom driver for the CSI modules. CSI1 is connected to an external video decoder (TW9990) in CCIR mode and CSI2 is connected to the internal VADC. On both channels I see memory corruption (writing behind the allocated buffer) when the video signal is disturbed (cable loose, camera loses power). I see this behavior even when only one channel is activated. Does anyone have an idea what can be wrong? I tried zillions of combinations of CSI settings and handling every interrupt source of the CSI module (used the linux driver as a reference). But I can't see that I am doing anything wrong now.

I get a perfect image as long as the camera signal(s) are stable. As soon as the signal get disturbed I get these annoying errors.

Any help is greatly appreciated.

Regards

Matthias

[igorpadykov]

Hi Matthias

seems dma overwrites data beyound buffer limits,

one can try to use some timer, checking frame start/end

and reset dma using DMA_REFLASH_RFF bit in CSICR3.

Best regards

igor

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[mod42]

So, you suggest that I setup a timer watching if the DMA is out of range? I don't think that's a clever approach as I can't guarantee a reaction time (Software may be doing other, more high priority things) As there is no such approach in the linux driver and I can't reproduce this behavior with the linux driver I suspect that there is some setup problem on my side. I have done intensive research with the linux and u-boot driver of the CSI but can't spot any major difference. Maybe there is something outside the CSI module which influences this behavior.

I already reset the DMA when an adress change error occurs (as suggested in the datasheet) but that doesn't change the behavior.

Do you have any other idea?

Regards

Matthias