SK-AM68: DisplayPort and SDK10

Hi T S,

It looks like our development team claims to have fixed this issue. Let me see if I can reproduce it on my end as well.

Regards,

Takuma

Hi T S,

To update you, I also see a similar thing as you. CRTC and the correct resolution is seen through kmsprint, but display is dark. 

Still discussing with our development team, but a lot of folks are out due to a holiday in India, so responses will be delayed most likely to early next week.

Regards,

Takuma

Thank you for the update!

Hi T S,

I have done some experiments on my end and was able to get display up by reverting the changes to the DSI to eDP driver back to 8.6 SDK. I have not cleaned it up to figure out which line is fixing/breaking, but wanted to share with you this update:

9_2_sdk_display_dark.zip

I think you are aware of the color flip issue, but that looks to be fixed. However, resolution is still fixed. So, the zip file has a patch that changes resolution to 1080p at about 38Hz in case you were wanting 1080p (which is non-standard and may not work on all monitors).

Still discussing with development team on how we can fix this up in a better way, but I wanted to share with you my findings in case you were blocked.

Regards,

Takuma

Takuma,

Thanks for the update!  I'll be interested to hear what the dev team comes back with.  Our custom hardware will include DisplayPort, so having an official solution will be nice.  I'll take a look at your patch and see where it gets me in the meantime.

Thanks again!

Hi T S,

Understood. Very reasonable asks. I will keep you updated with any new info I come across.

Regards,

Takuma

The patch unfortunately does not seem to work with my display.  Without the patch, I get 800x600 resolution output.  With the patch, I see a probe error which I'm guessing is an incompatibility error with my display.  I don't think it's worth your effort to spend any further time on this.  I'm fine with waiting for the dev team to come back with a long-term solution.

Hi T S,

Ok, understood. Does the screen continue to be blank with the patch, or the screen is visibly getting 800x600 resolution? If the screen is visibly getting 800x600 with the first patch, but second patch is causing screen to go blank, then yes, most likely it is an incompatible display resolution (the 38Hz is probably the issue).

Regards,

Takuma

I double-checked and I messed up the patch application.  The patches ultimately affect two kernel modules that are loaded at boot time - I only updated one of those modules.  Further, the patches didn't include a direct modification to the device tree that I'm using (k3-am68-sk-base-board.dts).  I updated my device tree to align with the patch changes for k3-j784s4-evm.dts, updated both kernel modules, and now upon booting my monitor presents a "Input Signal Out of Range!" warning and then goes to sleep.

With no patches applied, DisplayPort shows an 800x600 resolution as before.

Hi T S,

Apologies for that. Due to the board I had available, I did the patch for J784S4 EVM which should have the same DSI to eDP bridge as AM68 SK. 

But to clarify,

1. Before the patch on 10.0, the DisplayPort was a blank screen.

2. With the first patch, DisplayPort shows 800x600 resolution, with no issues in terms of color flips.

Are these statement correct? Because this is what I see on my end for 10.0 with just the first patch, and with a second patch for fixed 1080p resolution, some monitors will work at 1080p but many will not due to the non-standard frequency.

Regards,

Takuma

Sorry for the confusion.  I applied the changes to SDK 9, not SDK 10, and my comments were based on that context.

I'll re-apply against SDK 10 and let you know how it goes.

Do you have a patch set defined that targets SDK 10?  This does not work as-is for me

To be honest, though, I'm not sure if it is worth the effort to continue troubleshooting things.

Hi T S,

Ok, understood. The patches were on top of SDK 10.0 but are these being applied on the Linux source packaged in the SDK, or the source code is pulled from elsewhere, like git.ti.com or upstream Linux kernel? 

If you would like to pursue this, then I can see if I can port over the patch.

Regards,

Takuma

Takuma,

Hrm.  I tried applying your patch against what is in SDK 10 and saw several errors.  I also tried to set up a devshell session via bitbake and simply copied your included ti-sn65dsi86.c over-top of the base one and that failed when I issued "make -j $(nproc) modules".  The failure was due to the probe() function's incompatible pointer type - recent kernel refactoring has dropped the i2c_device_id parm.

Just to confirm -- your patch is for kernel 6.6.32, and NOT 6.1.80, correct?

Hi T S,

Yes, the patches are for 6.6 kernel for SDK 10.0... but let me double check that.

Regards,

Takuma

Hi T S,

Yes, can confirm that it is for 6.1.80.

Regards,

Takuma

Takuma,

That explains the failure.  I double-checked EdgeAI and J721S2 SDK 10 release notes and confirmed they target the 6.6 kernel.

Are you running some sort of alternative SDK 10 that targets 6.1.80?  I'm running the EdgeAI SDK 10 release.

SDK 10 release note references:

https://software-dl.ti.com/jacinto7/esd/processor-sdk-linux-am68a/10_00_00/exports/edgeai-docs/devices/AM68A/linux/release_notes_10_00.html

https://software-dl.ti.com/jacinto7/esd/processor-sdk-linux-j721s2/10_00_00_08/exports/docs/devices/J7_Family/linux/Release_Specific_Release_Notes.html

Hi T S,

Apologies again. I must have mixed up the kernels while doing some porting. I'll need a bit more time to look into this one. Development team has been notified, but they are a bit busy with a different display issue that is ongoing.

Regards,

Takuma

Any updates on this?

Hi T S,

No good updates yet. Regression seems to have happened around 9.2 SDK timeframe, and I am currently trying to pinpoint the exact change that caused display to not get enabled, so that it can be ported over to 10.0 SDK.

Regards,

Takuma

Hi T S,

Apologies for the long delay. 

There is a patch planned for 10.1 release for display, and applying to 10.0 SDK using AM68-SK board has made 800x600 resolution functional on my end: https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/commit/?h=ti-linux-6.6.y&id=118cf0c8b392bed94437f1519de10b63705dbacd

Could you also try the same?

Regards,

Takuma