IMX8M Mini EVK MIPI-HDMI Display

[先生孟]

Hi IMX8M Mini Team FAE:

    I want to use the IMX8M Mini EVK and MIPI2HDMI board to develop my application, I can't see any graphic or QT UI after the Linux kernel images are boot up ( the images are directly from office website of NXP and the version is 4.14.98_ga_2.0.0). The MIPI2HDMI board and HDMI screen function are good when I setup the environment value in the UBOOT:

$setenv panel MIPI2HDMI

when the Uboot is boot up, I can watch a logo image on the HDMI screen, but the the screen will turn black after the linux kernel completely boot up（I use the fsl-imx8mm-evk.dtb and Image for all IMX8）

So my question is : where should I be setup? UBOOT? or kernel ? 

Thank you !

[igorpadykov]

Hi LinJin

sect.Table 14. Known issues and workarounds for i.MX 8M attached

Release Notes describes issues with some monitors, so one can try others.

For running linux one can try to follow sect.4 Booting Linux OS Linux Guide,

try demos in folder /opt/imx-gpu-sdk/.

Best regards
igor
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[先生孟]

Hi igorpadykov:

  Thank you reply my question. I have seen the sect.Table 14. Known issues and workarounds in the Linux release Notes IMX8M mini Attached files

  the issues are listed as follows

  

     

   On above table, which means the 8M or 8M mini Quad will be fail with no display when setting mode in the DRM ?

but the 8Mmini has only the eLCDIF (MIPI-DSI) controller and without any DCSS, therefore, we have to use the MIPI2HDMI sub-board to debug 

our work. If the display problem listed by the table 14 is exist, what can I do next step? please give me suggestion. thank you very much!

Anyway, I test the my PC screen (support FullHD HDMI and EDID ) today, the following scripts are printed:

 

when I cat the modes: 

  $cat /sys/class/graphic/fb0/modes, the PC screen prefer resolution is 1360x768@60Hz

 (why here is 1360x768p-0 instead of 1360x768p-60? I don't understand !)

I add some resolution 1360x768 in the source code drivers/gpu/drm/drm_edid.c

static const struct drm_display_mode edid_cea_modes[] = {

   /* 108 - 1360x768p@60Hz 16:9 tony add 2019-06-20 */
{ DRM_MODE("1360x768", DRM_MODE_TYPE_DRIVER, 85500, 1360, 1424,
1536, 1792, 0, 768, 771, 777, 795, 0,
DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_PVSYNC),
.vrefresh = 60, .picture_aspect_ratio = HDMI_PICTURE_ASPECT_16_9, },

but it's not used! the PC screen is still turn black when the Linux kernel boot up

So what can I do ?

Thank you!

[igorpadykov]

Hi LinJin

>I add some resolution 1360x768 in the source code drivers/gpu/drm/drm_edid.c
>static const struct drm_display_mode edid_cea_modes[] = {
>but it's not used!

correct. Becasue hardware does not support other resolutions, except given

in struct drm_display_mode edid_cea_modes[].

>So what can I do ?

use monitor with standard "cea_modes" resolution.

Best regards
igor

[先生孟]

Hi igorpadykov:

  Thank you so much. according with your suggestion, I have to change the Panel screen following with the CEA mode table