imx8mp using dual out, HDMI and LVDS

[cthilo]

Hi

We need to use HDMI out and two LVDS out in parallel.

HDMI via the normal hdmi dts instance and LVDS via two adv7393 connected to ldb lvds channel0 and channel1.

With ldb lvds untouched, HDMI is working so far. Weston can start and use HDMI-A-1.

Then, I enable one of the adv7393 by adding the endpoints in
lvds-channel 0, port 1  and the hdmi part stops working and weston tells me, that there are no drm devices found.

How are the ldb and hdmi connected to each other, that the influence each other?

Any help is appreciated!

Kind regards
Thilo

[cthilo]

Hi Aldo

We build our own image based on yocto scarthgap. The kernel is linux-imx-tq with our own dts as we run on our own hardware (which can be the problem of course too).

meta-imx: scarthgap-6.6.52-2.2.2
meta-tq: scarthgap (latest)
meta-freescale: scarthgap (latest)

Our dts is based on the imx8mp-tqma8mpql-mba8mpxl.dts (as our hw uses the imx8mp SOM from TQ).

So, no not NXP EVK.

Could you still give me some hints?

Kind regards
Thilo

[AldoG]

Hello,

Sure will try to help, could you share the device tree so I can take a look at it?

Best regards/Saludos,
Aldo.

[cthilo]

Hi Aldo

here you are. Hopefully you see something.

There is a hdmi_cam_mux and a hdmi_cam_video_mux (commented out) which was a try to mux the hdmi in and the camera.

But this didn't work like this, as the imx8-media-dev.c:1041 expects the subdevs to be an i2c device but the video-mux isn't. If the rest would work, I don't know. Commenting this check out (easy test) did bring a kernel oops. So, not a good way.

Cheers
Thilo

[cthilo]

Hi Aldo

My answer was regarding another thread which I mixed up, but the Dts is correct.

Sorry for the confusion!

Cheers,
Thilo

[AldoG]

Hello,

I was trying to find if the problem was a device tree issue, but couldn't find much about the bindings for the adv7393, so couldn't say for sure.

I would suggest to try without the HDMI and see if the video encoder is detected by the system.
Also, have you checked the dmesg?
Is the encoder found and the driver working correctly?

Finally regarding your initial question one could refer to the reference manual Figure 13-1. Display, Imaging, Camera I/F Diagram & Figure 13-4. MEDIAMIX Block Diagram

Best regards/Saludos,
Aldo.

[cthilo]

Hi Aldo

so HDMI should not be related to the lvds out channels, when I interpret that overview correctly.

Anyway, I'll try to disable hdmi related stuff and test if the lvds setup only is working.

Here is a grep of ldb, adv73 and interconnect, as theses three are related as far as I understand.

[root@vci ~]# dmesg | grep "ldb\|adv73\|interconnect"
[ 0.069206] /ldb-display-controller/lvds-channel@0: Fixed dependency cycle(s) with /soc@0/bus@30800000/i2c@30a30000/adv7393@2a
[ 0.069265] /ldb-display-controller/lvds-channel@0: Fixed dependency cycle(s) with /soc@0/bus@32c00000/lcd-controller@32e90000
[ 0.069342] /ldb-display-controller/lvds-channel@1: Fixed dependency cycle(s) with /soc@0/bus@30800000/i2c@30a20000/adv7393@2b
[ 0.069392] /ldb-display-controller/lvds-channel@1: Fixed dependency cycle(s) with /soc@0/bus@32c00000/lcd-controller@32e90000
[ 1.522532] imx8mp-ldb ldb-display-controller: Failed to create device link (0x180) with 32e90000.lcd-controller
[ 1.532750] imx8mp-ldb ldb-display-controller: Failed to create device link (0x180) with 32e90000.lcd-controller
[ 2.009363] imx-bus-devfreq 32700000.interconnect: failed to fetch clk: -2
[ 2.016254] imx-bus-devfreq: probe of 32700000.interconnect failed with error -2
[ 2.322034] imx8mp-ldb ldb-display-controller: Failed to create device link (0x180) with 0-002b
[ 2.342605] imx8mp-ldb ldb-display-controller: Failed to create device link (0x180) with 1-002a
[ 2.384121] imx8mp-ldb ldb-display-controller: Failed to create device link (0x180) with phy-lvds
[ 2.393017] imx8mp-ldb ldb-display-controller: Failed to create device link (0x180) with phy-lvds
[ 8.633579] adv7393 0-002b: chip found @ 0x56 (30a20000.i2c)
[ 8.669132] imx8mp-ldb ldb-display-controller: Failed to create device link (0x180) with 0-002b
[ 8.669387] adv7393 1-002a: chip found @ 0x54 (30a30000.i2c)
[ 8.698574] imx8mp-ldb ldb-display-controller: Failed to create device link (0x180) with 1-002a

Can the failed probe of the interconnect be the problem?
I never touched the interconnect instance of the dtb, so I wonder how this can't work correctly?

The "Failed to create device link" errors are obvious but I can tell what caused it.

Could you tell me, what the cause can be for the "Failed to create device link" errors? 

Cheers,
Thilo

[AldoG]

Hello,

Could you share the BSP version that you are using?
Also, are you using NXP EVK?

Best regards/Saludos,
Aldo.