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Participant srdjan.opacic
Participant
255 Views
Registered: ‎08-21-2017

DisplayPort RX Subsystem, Video Mode change interrupt

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Hi,

I have a situation where a custom DP input is causing random interrupts for Video Mode change (mapped XDPRXSS_HANDLER_DP_VM_CHG_EVENT). I'm interested which parameters can cause this event - for now I verified that the resolution didn't change (read by function calls: XDp_ReadReg(DpRxSsInst.Config.DpSubCore.DpConfig.BaseAddr, XDP_RX_MSA_HRES); XDp_ReadReg(DpRxSsInst.Config.DpSubCore.DpConfig.BaseAddr, XDP_RX_MSA_VHEIGHT);).

Thanks

Srđan

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1 Solution

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Moderator
Moderator
235 Views
Registered: ‎11-09-2015

Re: DisplayPort RX Subsystem, Video Mode change interrupt

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Hi @srdjan.opacic ,

From my understanding, in most cases, the MSA values are set by the source but not through the AUX interface but through the main link.

Note that in DPCD register 0x007, it is possible for a sink to ignore the MSA values from the source but I do not think the DP RX SS allows this.

In reg 0x18, there is an option to filter the MSA value. Can you make sure this is set to 1?

dp2.JPG


Florent
Product Application Engineer - Xilinx Technical Support EMEA
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8 Replies
Moderator
Moderator
246 Views
Registered: ‎11-09-2015

Re: DisplayPort RX Subsystem, Video Mode change interrupt

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Hi @srdjan.opacic 

As per PG233:

dp.JPG

This interrupt should be triggered if there us a change in the MSA fields. You might want to check all the MSA fields, not only HRES and VRES.

Do you have the timing details for the resolution you are using?

Is it happening with multiple sources?

Regards,


Florent
Product Application Engineer - Xilinx Technical Support EMEA
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Participant srdjan.opacic
Participant
243 Views
Registered: ‎08-21-2017

Re: DisplayPort RX Subsystem, Video Mode change interrupt

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Hi @florentw ,

Thanks, I'll print all the fields, and get back to you. This is happening only with one source, which I don't have access to right now. I'll get this information from my customer, and get back to you. Am I correct to assume that you need MSA data to change, i.e. MSA update over the AUX channel? We are not talking about actual timing parameters of the video stream?

Thanks

Srdjan

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Moderator
Moderator
236 Views
Registered: ‎11-09-2015

Re: DisplayPort RX Subsystem, Video Mode change interrupt

Jump to solution

Hi @srdjan.opacic ,

From my understanding, in most cases, the MSA values are set by the source but not through the AUX interface but through the main link.

Note that in DPCD register 0x007, it is possible for a sink to ignore the MSA values from the source but I do not think the DP RX SS allows this.

In reg 0x18, there is an option to filter the MSA value. Can you make sure this is set to 1?

dp2.JPG


Florent
Product Application Engineer - Xilinx Technical Support EMEA
**~ Don't forget to reply, give kudos, and accept as solution.~**
Participant srdjan.opacic
Participant
201 Views
Registered: ‎08-21-2017

Re: DisplayPort RX Subsystem, Video Mode change interrupt

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Hi @florentw ,

MSA filtering is definitely turned off - content of the register is 0x2, set in SW to force use of DEFERs instead of partial ACKs. I think this was also the case in original Xilinx reference design - should I use MSA filtering by default, or are there any negative sideffects which caused this to be turned off in the first place?

Thanks

Srdjan

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Moderator
Moderator
192 Views
Registered: ‎11-09-2015

Re: DisplayPort RX Subsystem, Video Mode change interrupt

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Hi @srdjan.opacic ,

I talked with development and they told me it is safe to set this bit.

The behaviour you are experiensing interest them and they've never seem this. Is it possible for you to monitor all the MSA fields and let me know which one is chaning if any?

Thanks

 


Florent
Product Application Engineer - Xilinx Technical Support EMEA
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Participant srdjan.opacic
Participant
188 Views
Registered: ‎08-21-2017

Re: DisplayPort RX Subsystem, Video Mode change interrupt

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Hi @florentw ,

Thanks, I'll let you know if it helped.

No problem for monitoring MSA fields, I'll wait for my customer to catch the error again (it is not really easy to catch, one event per several hours) before moving to filtering. I'm also interested in which field exactly changes, I see no reason for any of them to do so.

Thanks

Srdjan

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Participant srdjan.opacic
Participant
167 Views
Registered: ‎08-21-2017

Re: DisplayPort RX Subsystem, Video Mode change interrupt

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Hi @florentw ,

Unfortunately my customer is unable to repeat the error :(. Latest information seems to point to the fact that the adapter in question (i.e. DP source) is to blame for this, so I'll stop working on this problem until we verify the cause. Thanks for your help, I'll keep MSA filtering in mind for future  problems like this - currently I'm unable to cause the Video Mode Change interrupt, so I cannot test filtering and see if it helps in any way.

Best regards

Srdjan

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Moderator
Moderator
159 Views
Registered: ‎11-09-2015

Re: DisplayPort RX Subsystem, Video Mode change interrupt

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Hi @srdjan.opacic ,

Thank you for letting me know. Hopefully it will not happen again ;)


Florent
Product Application Engineer - Xilinx Technical Support EMEA
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