i.MX8MP allow HDMI to output 1920x1080-59.94Hz

[RU_Callum]

Hello,

I'm currently working with the i.MX8MP processor for a video playback project and have encountered an issue: I’m unable to get HDMI to output at 1920x1080-59.95Hz. I do not require dynamic refresh rate switching — I simply need a stable output at this fixed refresh rate.

The hardware platform I’m using is based on SolidRun's HummingBoard Pulse:
https://developer.solid-run.com/knowledge-base/hummingboard-pulse-getting-started/

I’m running Yocto 4.0 Kirkstone, using NXP Embedded Linux 5.15.71-2.2.0.

I’ve previously posted on the SolidRun forums but haven’t had any success resolving the issue.

I’ve found similar discussions related to this topic, such as this one:
https://community.nxp.com/t5/i-MX-Processors/imx8mp-programming-hdmi-phy-pll-timings/td-p/1498162

If anyone has experience with configuring fixed HDMI output timings on this platform — or can point me toward the relevant device tree modifications or driver changes — I would greatly appreciate your assistance.

Thank you!

[pengyong_zhang]

Hi @RU_Callum 

For imx8MP HDMI pixel clock's clock source is IMX8MP_CLK_24M.

B.R

[pengyong_zhang]

hI @RU_Callum 

Sorry about that, i.MX8MP does not support 148.352MHz. pixel clock output.

B.R

[RU_Callum]

Hello @pengyong_zhang,

Thank you for your assistance. As a last attempt to achieve this clock rate, could you let me know which specific clock is used as reference for the creation of the HDMI output.

We are considering replacing this clock with a 0.1% slower clock reference on our PCB design, that would allow for an output of 148.352MHz

Best Regards

[pengyong_zhang]

Hi @RU_Callum 

I have tested on my i.MX8MP evk board about 1920x1080@59.94Hz, We do not support 148.352MHz pixel clock. And i can not get your panel pixel clock about your link. You need to check about the datasheet file. And we can support the  148.5MHz pixel clock.

B.R

[RU_Callum]

Hi @pengyong_zhang,

Thanks for the response, is there any way to force this 148.352MHz pixel clock rate on the i.MX8MP ?

The reason I want this mode is to comply with the NTSC (National Television System Committee) standards.

Any help in achieving this would be greatly appreciated.

Many thanks!

[pengyong_zhang]

hI @RU_Callum 

I have ask you the question for twice :  What is your panel pixel clock? share your panel's datasheet file.

If we do not support your panel pixel clock, Your panel will not display properly

B.R

[RU_Callum]

Hi @pengyong_zhang,

I appreciate that you have asked this question twice, the reason I've avoided it, is because it has been tested on several different broadcast monitors.

Here is the specs of the monitor I'm currently using:

Monitor: https://lilliputdirect.com/A11

Specification sheet: https://drive.google.com/file/d/1fhSdyPbVu6ukpm33yqDd64ruyZZABC1y/view

Signal format table: https://drive.google.com/file/d/1th2s5CekSFQxn5pyLvvqshyA9tPOu_ut/view

Many thanks.

[pengyong_zhang]

Hi @RU_Callum 

Change the westom.ini file at the /etc/xdg/weston location, Change the resolution you want in [output] part.

BTW : What is your panel pixel clock? share your panel's datasheet file.

B.R

[RU_Callum]

Hi @pengyong_zhang,

I have changed the weston.ini file, and it still seems to default back to 60Hz.

The HDMI output is being fed into an HDMI to 3G/HD-SDI converter: https://aivion.com/wp-content/uploads/DS_A_NA1012B_ET_V1.0.2.pdf

This converter expects the following clock rates to be fed to it from the HDMI connection:

The HDMI/DVI TMDS input clock requirements are:
3G mode:
148.5MHz or 148.5 MHz/1.001 +/- 60ppm
HD mode:
74.25MHz or 74.25MHz/1.001 +/- 80 ppm

We have tested the converter, and when it receives clock rate of 148.5/ MHz/1.001 it will play at 59.94Hz. This suggests that the i.MX8MP is not outputting at this rate, even when changing the weston.ini

Is there a way to force this clock rate on the i.MX8MP?

Many Thanks 

[pengyong_zhang]

Hi @RU_Callum 

pleas share your full result log file. Also what is your panle pixel clock? If os, please share your panle's datasheet file.

B.R

[RU_Callum]

Hi @pengyong_zhang

These patch notes seem to address the problem in question, but I have been unable to apply any changes to my board that resolve this issue. Hope this is helpful:

https://lore.kernel.org/linux-arm-kernel/819380c3-d13f-4989-b305-388fc60d30e4@nxp.com/

Thanks

[RU_Callum]

Full log:

root@imx8mpsolidrun:~# modetest
trying to open device 'i915'...failed
trying to open device 'amdgpu'...failed
trying to open device 'radeon'...failed
trying to open device 'nouveau'...failed
trying to open device 'vmwgfx'...failed
trying to open device 'omapdrm'...failed
trying to open device 'exynos'...failed
trying to open device 'tilcdc'...failed
trying to open device 'msm'...failed
trying to open device 'sti'...failed
trying to open device 'tegra'...failed
trying to open device 'imx-drm'...done
Encoders:
id crtc type possible crtcs possible clones
40 0 DSI 0x00000001 0x00000001
42 39 TMDS 0x00000004 0x00000002

Connectors:
id encoder status name size (mm) modes encoders
41 0 disconnected HDMI-A-1 0x0 0 40
props:
1 EDID:
flags: immutable blob
blobs:

value:
2 DPMS:
flags: enum
enums: On=0 Standby=1 Suspend=2 Off=3
value: 0
5 link-status:
flags: enum
enums: Good=0 Bad=1
value: 0
6 non-desktop:
flags: immutable range
values: 0 1
value: 0
4 TILE:
flags: immutable blob
blobs:

value:
43 42 connected HDMI-A-2 710x400 14 42
modes:
index name refresh (Hz) hdisp hss hse htot vdisp vss vse vtot
#0 1920x1080 60.00 1920 2008 2052 2200 1080 1084 1089 1125 148500 flags: phsync, pvsync; type: driver
#1 1920x1080 59.94 1920 2008 2052 2200 1080 1084 1089 1125 148352 flags: phsync, pvsync; type: driver
#2 1920x1080 50.00 1920 2448 2492 2640 1080 1084 1089 1125 148500 flags: phsync, pvsync; type: driver
#3 1920x1080 30.00 1920 2008 2052 2200 1080 1084 1089 1125 74250 flags: phsync, pvsync; type: driver
#4 1920x1080 29.97 1920 2008 2052 2200 1080 1084 1089 1125 74176 flags: phsync, pvsync; type: driver
#5 1920x1080 25.00 1920 2448 2492 2640 1080 1084 1089 1125 74250 flags: phsync, pvsync; type: driver
#6 1920x1080 24.00 1920 2558 2602 2750 1080 1084 1089 1125 74250 flags: phsync, pvsync; type: driver
#7 1920x1080 23.98 1920 2558 2602 2750 1080 1084 1089 1125 74176 flags: phsync, pvsync; type: driver
#8 1280x720 60.00 1280 1390 1430 1650 720 725 730 750 74250 flags: phsync, pvsync; type: driver
#9 1280x720 59.94 1280 1390 1430 1650 720 725 730 750 74176 flags: phsync, pvsync; type: driver
#10 1280x720 50.00 1280 1720 1760 1980 720 725 730 750 74250 flags: phsync, pvsync; type: driver
#11 720x576 50.00 720 732 796 864 576 581 586 625 27000 flags: nhsync, nvsync; type: driver
#12 720x480 60.00 720 736 798 858 480 489 495 525 27027 flags: nhsync, nvsync; type: driver
#13 720x480 59.94 720 736 798 858 480 489 495 525 27000 flags: nhsync, nvsync; type: driver
props:
1 EDID:
flags: immutable blob
blobs:

value:
00ffffffffffff002301000001000000
0a190103804728960adaffa3584aa229
17494b00000001010101010101010101
010101010101011d8018711c1620582c
2500c48e2100009e011d007251d01e20
6e285500c48e2100001e000000fc0042
4d442048444d490a20202020000000fd
00173c1f440f000a20202020202001c1
020321774d858487949396a0a1a29f90
0312230f040783ff000066030c000000
008c0aa01451f01600267c4300138e21
000098011d80d0721c1620102c2580c4
8e2100009e011d00bc52d01e20b82855
40c48e2100001e8c0aa0205120181018
7e2300138e21000098011d803e73382d
407e2c4580c48e2100001e0000000034
2 DPMS:
flags: enum
enums: On=0 Standby=1 Suspend=2 Off=3
value: 0
5 link-status:
flags: enum
enums: Good=0 Bad=1
value: 0
6 non-desktop:
flags: immutable range
values: 0 1
value: 0
4 TILE:
flags: immutable blob
blobs:

value:
44 max bpc:
flags: range
values: 8 16
value: 0

CRTCs:
id fb pos size
33 0 (0,0) (0x0)
#0 nan 0 0 0 0 0 0 0 0 0 flags: ; type:
props:
24 VRR_ENABLED:
flags: range
values: 0 1
value: 0
36 0 (0,0) (0x0)
#0 nan 0 0 0 0 0 0 0 0 0 flags: ; type:
props:
24 VRR_ENABLED:
flags: range
values: 0 1
value: 0
39 49 (0,0) (1920x1080)
#0 1920x1080 60.00 1920 2008 2052 2200 1080 1084 1089 1125 148500 flags: phsync, pvsync; type: driver
props:
24 VRR_ENABLED:
flags: range
values: 0 1
value: 0

Planes:
id crtc fb CRTC x,y x,y gamma size possible crtcs
31 0 0 0,0 0,0 0 0x00000001
formats: XR24 AR24 RG16 XB24 AB24 AR15 XR15
props:
8 type:
flags: immutable enum
enums: Overlay=0 Primary=1 Cursor=2
value: 1
32 zpos:
flags: immutable range
values: 0 0
value: 0
34 0 0 0,0 0,0 0 0x00000002
formats: XR24 AR24 RG16 XB24 AB24 AR15 XR15
props:
8 type:
flags: immutable enum
enums: Overlay=0 Primary=1 Cursor=2
value: 1
35 zpos:
flags: immutable range
values: 0 0
value: 0
37 39 49 0,0 0,0 0 0x00000004
formats: XR24 AR24 RG16 XB24 AB24 AR15 XR15
props:
8 type:
flags: immutable enum
enums: Overlay=0 Primary=1 Cursor=2
value: 1
38 zpos:
flags: immutable range
values: 0 0
value: 0

Frame buffers:
id size pitch

Using Weston i was able to pull the following:

[13:12:40.811] Output HDMI-A-2 (crtc 39) video modes:
1920x1080@60.0 16:9, current, 148.5 MHz
1920x1080@59.9 16:9, 148.4 MHz
1920x1080@50.0 16:9, 148.5 MHz
1920x1080@30.0 16:9, 74.2 MHz
1920x1080@25.0 16:9, 74.2 MHz
1920x1080@24.0, 74.2 MHz
1920x1080@24.0 16:9, 74.2 MHz
1280x720@60.0, 74.2 MHz
1280x720@60.0 16:9, 74.2 MHz
1280x720@59.9 16:9, 74.2 MHz
1280x720@50.0, 74.2 MHz
1280x720@50.0 16:9, 74.2 MHz
720x576@50.0 16:9, 27.0 MHz
720x480@60.0 16:9, 27.0 MHz
720x480@59.9 16:9, 27.0 MHz

however when i set Weston to output at 1920x1080@59.94 it defaults back to 60Hz

Many Thanks.

[pengyong_zhang]

HI @RU_Callum 

Please typr the  modetest -C  commnd and share the result?

B.R

[RU_Callum]

Hi @pengyong_zhang,
Thanks for your quick response,

root@imx8mpsolidrun:~# modetest -C
trying to open device 'i915'...failed
trying to open device 'amdgpu'...failed
trying to open device 'radeon'...failed
trying to open device 'nouveau'...failed
trying to open device 'vmwgfx'...failed
trying to open device 'omapdrm'...failed
trying to open device 'exynos'...failed
trying to open device 'tilcdc'...failed
trying to open device 'msm'...failed
trying to open device 'sti'...failed
trying to open device 'tegra'...failed
trying to open device 'imx-drm'...done

I don't know if this is helpful, but i'm using Weston compositor to display the video playback.