Graphics
Intel® graphics drivers and software, compatibility, troubleshooting, performance, and optimization
21589 Discussions

VGA modes on HDMI and (e)DP

B-OatPQURE
New Contributor I
937 Views

Hi,

 

It's not clear how to set the clocks for the VGA mode 00h - 13h for HDMI and (e)DP ports. In the formula for setting the PLL clock you may use a multiplier, to get the frequency over 100 MHz. For the VGA modes, the multiplier can be set to 4 to get the 25.175 MHz frequency to 100.700 MHz for example. This can not be applied to either HDMI or (e)DP ports however.

 

For the HDMI port data is sent with using the same VGA frequency but with 10 bits per pixel. The dot clock will match both ends. It seems resonable that both the dot clock and the HDMI link clock should be 25.175MHz. In the DPLL control register a divide by 10 value should be used for frequencies <= 270 MHz. Thus the 25.175Hz may create a HDMI bit rate clock of 251.75 MHz? The problem is that the logic between the in frequency and the out frequency is not specified at all in the HDMI case. Thus programming the PLL logic to the right frequency is a guess work at best.

 

For (e)DP it's clearer. Here you have the fixed link clocks of 162, 270 or 540 MHz. You also have the transfer registers where you can compute M and N values for the dot clock and the link clocks.

 

I need a clarification of how to program the VGA mode clocks. Not details, just the input needed to get the right frequency out at the other end. In between those ends, you may have some internal dividing and multiplying, that may be relevant or not. In that case I want to know the basics of that, not the details of compensation for number of color bits, lanes etc.

 

Best regards,

 

Berth-Olof Bergman

PQURE Technology

 

0 Kudos
5 Replies
RamyerM_Intel
Moderator
889 Views

Hello B-OatPQURE , 


Thank you for posting in the communities. In order to help you with your request, may I please know what product you need in the clarification of how to program the VGA mode clocks? Additionally, may I please know why you need this information? You may also let me know if you prefer to continue our conversation by email. 


Ramyer M. 

Intel Customer Support Technician 



0 Kudos
B-OatPQURE
New Contributor I
880 Views

Hi Ramyer,

 

Thank you for your reply!

 

I started a project for several platforms based on Cherryview architecture. Some are maker boards based on Z8350 from 3 vendors. Another platform is a dual ethernet security device based on N3050.

First I was adopting our BIOS to FSP. The DRAM initialisation part worked, but it hanged for some obscure reason in the silicon initialisation part. So I had to make my own DRAM initialisation and training code as Intel would not provide me with the MRC code.

After have finishing the DRAM initialisation code and my own silicon initialisation the BIOS was finished and working.

I had hope to use the VBIOS for the architecture and I had 3 binary versions of it. I have used Intel VBIOS in the past, but I didn't have the configuration tool. So I couldn't  configure the VBIOS. I have previously received reference code and tools, but for some reason I couldn't get the configuration tool for Cherryview VBIOS. So I had to develop my own VGA BIOS. It is completed with APIs compatible with VBIOS, but there are some details to solve regarding the relationships between the PLL input and transcoder output.

 

I have been in bad luck here, as I had to do everything on my own. Previously, I got everything I wanted from Intel in the Baytrail projects. I developed the BIOS for Rafael in Israel in cooperation with Kontron and Rafael.

I do have a SNDA with Intel, but I have not gotten any help I have requested. I would gladly use VBIOS if I could get the configuration tool. It's not that fun to develop a VGA BIOS. The thing is that I have a mass production security product based on N3050 and we plan to mass produce several products based on the Cherryview architecture.

I know it's EOL for Cherryview, but the companies involved in this project have no plans to stop using the architecture. I hope you can help me solve this situation. The configuration tool would be a great help as I will be able to use VBIOS. Otherwise I need to complete my own VGA BIOS. Best would be to get clock relation ship sorted out and the configuration tool to use VBIOS until the VGA BIOS is debugged and completed.

 

You can email me directly to b-o@pqure.com

 

Best regards,

 

Berth-Olof Bergman

PQURE Technology

0 Kudos
그래요ITech
New Contributor I
847 Views

Hey there @B-OatPQURE

...You've encountered quite a challenge with the Cherryview architecture, especially without the configuration tool for the VBIOS. Developing your own VGA BIOS is no small feat, and it's understandable that you'd prefer to use the VBIOS with the appropriate tool if possible.

While I can't directly assist with obtaining the configuration tool or resolving the clock relationship issues, I can offer some general advice:

1. Ensure that you've reviewed all available documentation for the Cherryview architecture and the VBIOS binaries you have. Sometimes, documentation can provide insights or workarounds that might not be immediately apparent.
2. Engage with community forums or user groups focused on BIOS development, Other developers may have faced similar issues and could offer guidance or share their solutions.

Continue to refine your own VGA BIOS as a backup plan. While it's not the ideal solution, having a functional custom BIOS could be invaluable if the configuration tool remains unavailable.

I understand this situation is far from ideal, but I hope these suggestions can help you navigate the challenges you're facing. Best of luck with your project... and I hope you'll be able to find a resolution soon.

 

Cheers,

Max

0 Kudos
RamyerM_Intel
Moderator
735 Views

Hello B-OatPQURE, 


Apologies for the delay in our response. For now I will be coordinating this request with our team and give an update to this post as soon as possible. Thank you for your patience and cooperation. 


Ramyer M.

Intel Customer Support Technician 



0 Kudos
RamyerM_Intel
Moderator
632 Views

Hello B-OatPQURE, 


Upon coordinating with our team about your product, we found out that the interactive support for Cherryview and Braswell Architecture has already reached its end. I understand that this is not the answer that you were expecting, and we sincerely apologize for any inconvenience this may have caused. Since support for this product has already ended, we no longer respond to telephone, chat, community support forum, or email inquiries. You may still receive suggestions from our fellow community users. For now, we will proceed with closing this case. We wish you the best in your future endeavors! 


Ramyer M. 

Intel Customer Support Technician 


0 Kudos
Reply