HDMI Display not working in release/qcomlt-4.14 branch

Products Support DragonBoard 820c
#1

Hi all,
I have two questions.

  1. HDMI display is not working in release/qcomlt-4.14.
  2. Sd card is working in this branch since it uses 4.14.53 kernel. Any idea about the fix applied for sd card? so that atleast it can be integrated to 4.14.15 kernel?

Below are the error logs. mdss probe is not happening. drm won’t be initialized.
Anyone have idea ?

[ 18.944298] drm: Unknown symbol __clear_user (err 0)
[ 18.960159] Bluetooth: HCI UART protocol QCA registered
[ 18.963252] media: Linux media interface: v0.10
[ 18.965411] videodev: Unknown symbol raw_copy_in_user (err 0)
[ 18.975025] Bluetooth: hci0: ROME setup
[ 18.975029] Bluetooth: hci0: Set UART speed to 3000000
[ 18.981151] videodev: Unknown symbol raw_copy_in_user (err 0)
Thanks,
Pradeep

#2

HDMI display is not working in release/qcomlt-4.14.
Sd card is working in this branch since it uses 4.14.53 kernel. Any idea about the fix applied for sd card? so that atleast it can be integrated to 4.14.15 kernel?

Below are the error logs.
Anyone have idea about error logs?

[ 18.944298] drm: Unknown symbol __clear_user (err 0)
[ 18.960159] Bluetooth: HCI UART protocol QCA registered
[ 18.963252] media: Linux media interface: v0.10
[ 18.965411] videodev: Unknown symbol raw_copy_in_user (err 0)
[ 18.975025] Bluetooth: hci0: ROME setup
[ 18.975029] Bluetooth: hci0: Set UART speed to 3000000
[ 18.981151] videodev: Unknown symbol raw_copy_in_user (err 0)

Are your kernel boot image and kernel modules (on root filesystem) in
sync. Symbol errors should be pretty rare (and if they exist the kernel
build system would have emitted warnings about it before you ever tried
to run the kernel).

#4

Thanks @danielt . I synced kernel modules in rootfs. Now there are no issues. Both display and sd card works fine.

#5

Hi Pradeep,
I am needing sd card working as well in qcom 4.14. I’m a little confused by which version are you using and how can I get it :slight_smile: The version you are using works on the db820c? Could you send me a link to the source or binaries so I can also try.
Thanks,
Kim

#6

Hi @kimbo,

Just fast forward the kernel branch. It will work :wink:

Thanks,
Pradeep

#7

Hi Pradeep,

Fast forward is a git thing? Sorry but I am not familiar with git :frowning:
Would you tell me the git command to type?

Thanks,
kimbo

#8

Just run below commands from your kernel source, let me know if you face any issue.

git fetch --all
git pull

#9

If it asks you for remote, then run below commands.
I don’t remember remote name, one of below commands will work.
git pull origin release/qcomlt-4.14
git pull master release/qcomlt-4.14

#10

Hi Pradeep,
I was able to execute the git fetch and git pull commands. Then I built the kernel. I do not see the hdmi display coming up. Ethernet seems to be working. Any suggestions? Do I need to flash a new rootfs?

Thanks,
Kim

#11

You need to build kernel modules as well and put them in rootfs at /lib/modules, since display drivers (drm/msm) are built as modules. You will get hdmi console initially. To get to UI, you need to type/give some random keyboard events(it’s introduced in newer kernels for security purposes). you can also get to UI directly by doing the below change in kernel. drivers/char/random.c
crng_init>0, instead of crng_init>1

#12

After copying the /lib/modules/kernel and /lib/modules/ to the file system, now the SD card is working!
Thank you so much Pradeep :slight_smile:
Kimbo

#13

Welcome kimbo

Thanks
Pradeep

#14

Data transfer of class 10 UHS cards is still an issue. Class4 cards are working fine.

#15

Hi Pradeep,

When you say data transfer, do you mean writing to the card (to be clear)? I was using a class 10 sd card and it seemed to work for me. I was able to read and write to card…at least it showed new files written and they were not 0B after writing. It was formatted as vfat. I am using a SOM by Inforce which has the same snapdragon chip as the dragonboard 820c. I believe I had to mount the card as writable though or it came up as read only. Anything I can try to disprove this? I do have a dragonboard 820c which had mounted the sd card as ro.

Thanks,
Kimbo

#16

Hi @kimbo,

I meant read/write. I formatted sd card in ext4 format. I will try with vfat and let you know.

Thanks,
Pradeep

#17

Hi Pradeep,

I tried sd card as ext4 and you are correct that it does not work for a class 10 card. I get an error and the sd card is reformatted as read only. I also did more testing when I format the sd card as vfat and it seems to randomly work. So it is not 100%, which is unfortunate.

Thanks,
Kim

#18

@kimbo,

Only Class 4 SD card works fine. Do you have class 6 card to test?

Thanks,
Pradeep

#19

Hi Pradeep,

I do not have any class 6 cards to tests. It seems our most common is the class 10.

Thanks,
Kim