Apalis T30 Mainline Kernel 4.12.1 HDMI issue

Dear Toradex Support,
I had compiled Mainline kernel 4.10.0 for Apalis T30 based on one of your articles and it was all fine.
I had all drivers loaded ,have Ethernet after applying your patch mentioned in the article and also had HDMI output.

Now, I tried to upgrade my kernel to 4.12.0-rc5 which is the latest stable release. However, after successful compilation, all are working fine except I do not have HDMI.
I only have serial output, and of course Ethernet is working fine too.

May I kindly ask your to advise if there is anything changed in Device Tree making this problem happens or there are something else?
Can you please advise if I can fix by applying any patch our something to get HDMI working?

Your help will be much appreciated
Many thanks,

Just as an update, the environment has not changed.
HDMI output works fine if I use uImage, DTB file and 4.10.0 modules and if I switch to uImage, DTB and Module from 4.12.0-rc5 , then the HDMI does not work.

No U-Boot change and all are in same environment, same rootfs,…

So it’s certainly Kernel making this happens!

Thanks

# dmesg | grep hdmi
[    0.000000] Kernel command line: core_edp_mv=1300 usb_high_speed=1 ip=off root=/dev/mmcblk2p2 rw,noatime rootfstype=ext3 rootwait igb_mac=00:14:2d:28:e7:aa consoleblank=0 no_console_suspend=1 console=tty1 console=ttyS0,115200n8 debug_uartport=lsport,0 vmal,1920x1080M
[    3.287718] tegra-hdmi 54280000.hdmi: 54280000.hdmi supply hdmi not found, using dummy regulator
[    3.296699] tegra-hdmi 54280000.hdmi: failed to get PLL regulator
[    4.295570] tegra-hdmi 54280000.hdmi: 54280000.hdmi supply hdm

Dear Toradex Support, I had compiled Mainline kernel 4.10.0 for Apalis T30 based on one of your articles and it was all fine.

So out of what exact reason did you not stay with what worked?

I had all drivers loaded ,have Ethernet after applying your patch mentioned in the article and also had HDMI output.

Now, I tried to upgrade my kernel to 4.12.0-rc5 which is the latest stable release.

I guess you got some concepts wrong. The rc5 in that version number means it is of release candidate quality and definitely nothing stable!

However, after successful compilation, all are working fine except I do not have HDMI. I only have serial output, and of course Ethernet is working fine too.

May I kindly ask your to advise if there is anything changed in Device Tree making this problem happens or there are something else? Can you please advise if I can fix by applying any patch our something to get HDMI working?

I really don’t know. I quickly gave latest rc a try and it truly seems broken. Basically the drm driver does not seem to get loaded at all anymore. Why exactly that is we will have to find out.

Your help will be much appreciated Many thanks,

You are very welcome and thanks for letting us know.

Dear Marcel,
Many thanks for your reply.
Regarding your terms about stable releases, I would mentioned that the Release Candidates also have Stable Status as well.
Please check here: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git

And from name of the file, you can see that the 4.12-rc5 is stable, but is Release Candidate:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/snapshot/linux-stable-4.12-rc5.tar.gz

Anyway, I appreciate your time for answering me, and hope the kernel works fine in full release 4.12.0

No, a release candidate is really just a release candidate and has absolutely nothing to do with being any stable in any way at all! Plus release candidates should really only ever be used by developers who do know what they are doing. Anybody else should really not bother ever touching any such!

Please see the following patch which fixes this. Alternatively moving forward one may actually make use of the IOMMU by enabling it e.g. in the tegra30.dtsi analogue to how the following patch does this for TK1.

Dear all/Marcel,
Now that the kernel 4.12.1 is out, I again tried to compile the mainline kernel for Apalis T30 and same as before there is not any display out (HDMI out) at all.
Is there anything you can help to fix?

P.S: Serial output showing the boot sequence properly and I see the login prompt in serial but no display on HDMI at all!

I don’t think the patch I previously mentioned has made it in yet. Please be patient.

Dear Marcel,
I have applied the patch manually and now I have HDMI output.

Thank you

You are very welcome.