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SN65DSI83-Q1: Random vertical sync issue

Part Number: SN65DSI83-Q1

Hello,

We are using Raspberry Pi CM4 and SN65DSI83-Q1 chip together with Ampire display. We are having issue that sometimes, perhaps once in 100 starts of our system the display is not displaying proper data viz included video. It seems like some vertical sync issue and some lines are displayed on different places than they should be. 

We found out that we can sometime  fix this issue by turning off/on PLL by setting the PLL_EN register on SN65DSI83-Q1, this although doest not work every time so we might have to turn it off and on multiple times to get it fixed.  We tried to display the test pattern to see if the issue is with DSI signal going form CM4 SN65DSI chip but with no help because all lines are vertical in test pattern so the vertical sync issue does not effect that specific picture (unlucky). 

Is there any way we could maybe display different test pattern?

Any ideas what could be causing this? 

I dont think this is a timing issue becuase it really seems like it happens randomly and I assume if we had timings for our display wrong this would happend more often. We tried to play with timings of the display in linux kernel but with no luck.

Thank you.