topic Re: imx8mp LVDS double screen problem in i.MX Processors

imx8mp LVDS double screen problem

JackSp — Thu, 02 Nov 2023 08:06:05 GMT

Hi,

I would like to SD output 576i format data from LVDS interface using imx8mp SOM. So, i used to DS90CR286 for LVDS to TTL parallel converter and also used adv7341 for analog video converter.

Firstly, I modified my yocto image (5.15.71 kirkstone) for pixel clock=27MHz and resolution 720x576 using patch file. I generated test pattern using adv7341 board on 576i format clearly in this configuration.

When i want to took LVDS output, i had double screen.

I think, i need to progressive to interlaced video conversion. So i added to “interlaced” flag to my “panel-timing” node (you can see in my patch file) and then i got “Failed to start Weston, a compositor, as a system service.” fail.

Is there any way to convert data format progressive to interlace for LVDS output using imx8mp SOM?

Do you have any suggestion for this issue? I added the patch file and log file in the attachments.

Thank you for your help.

Re: imx8mp LVDS double screen problem

Sanket_Parekh — Thu, 02 Nov 2023 11:43:56 GMT

Hi @JackSp,

I hope you are doing well.

Make sure the connections of IMX-LVDS-HDMI are proper.

Please make sure to have hardware configuration in the device tree.

Please refer to Chapter 13: Display, Imaging, and Camera of i.MX8 Reference Manual.

Please refer to Chapter 10: Wayland and Weston of i.MX Graphics user guide.

Some patches of 'Add i.MX8MP LVDS driver in uboot' are available over Here.

- i.MX8MP Custom Board LVDS Display

- different lvds support on imx8mp

- iMX8 - Problems bringing up LVDS

Thanks and Regards,
Sanket Parekh

Re: imx8mp LVDS double screen problem

JackSp — Mon, 13 Nov 2023 13:24:39 GMT

Hi Sanket,

I have another issue about this problem. I got below message while booting image,

[ 6.308408] imx-drm display-subsystem: bound imx-lcdifv3-crtc.0 (ops lcdifv3_crtc_ops)

[ OK ] Created slice Slice /system/systemd[ 6.320968] imx-drm display-subsystem: bound 32c00000.bus:ldb@32ec005c (ops imx8mp_ldb_ops)

-backlight.

[ 6.331538] [drm] Initialized imx-drm 1.0.0 20120507 for display-subsystem on minor 1

[ 6.340020] imx-drm display-subsystem: [drm] Cannot find any crtc or sizes

Then i checked the drm utilities using this command

root@ucm-imx8m-plus:~# modetest -M imx-drm

Encoders:

id crtc type possible crtcs possible clones

34 0 LVDS 0x00000001 0x00000001

Connectors:

id encoder status name size (mm) modes encoders

35 0 connected LVDS-1 270x200 0 34

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:

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

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

Frame buffers:

id size pitch

Above logs about image with interlaced flag and, CRTCs parameters not setted.
I share logs below about image without interlaced flag.

root@ucm-imx8m-plus:~# modetest -M imx-drm

Encoders:

id crtc type possible crtcs possible clones

34 33 LVDS 0x00000001 0x00000001

Connectors:

id encoder status name size (mm) modes encoders

35 34 connected LVDS-1 270x200 1 34

modes:

index name refresh (Hz) hdisp hss hse htot vdisp vss vse vtot

#0 720x576 25.00 720 740 804 864 576 590 591 625 13500 flags: nhsync, nvsync; type: preferred, driver

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:

CRTCs:

id fb pos size

33 40 (0,0) (720x576)

#0 720x576 25.00 720 740 804 864 576 590 591 625 13500 flags: nhsync, nvsync; type: preferred, 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 33 40 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

Frame buffers:

id size pitch

In these logs, CRTCs parameters setted.
Do you have any advise or solution about this problem? Why i get crtc or size error?

Thank you for your reply.

Re: imx8mp LVDS double screen problem

Sanket_Parekh — Mon, 20 Nov 2023 12:45:39 GMT

Hi @JackSp,

I hope you are doing well.

- A CRTC represents the overall display pipeline. It receives pixel data from drm_plane and blends them together.

- The drm_display_mode is also attached to the CRTC, specifying display timings.

- As we have gone through such cases before, it might be a hardware problem.

- After it gets solved, one might need to make a slight timing adjustment, using the boundary device's timing in their device tree node.

- However it has been reported before but is fixed in the latest kernel version, so please make sure to use the latest Linux version.

- In the updated device tree, it might be possible for any misspelling or typing mistakes, which we have found in many of the cases before.

- One may find the solution from our close to a similar case.

- Problems faced during LVDS.

- struct drm_crtc_funcs: control CRTCs for a given device

Thanks and Regards,
Sanket Parekh