How to set LVDS as default panel

xiaochao0131 · ‎07-27-2016

I installed ubuntu Image in my iMX6 sabre lite board.
I want to use LVDS as default output, so I changed the u-boot environment as below:

setenv bootargs_mmc 'setenv bootargs ${bootargs} root=/dev/mmcblk1p1 rootwait rw video=mxcfb0:dev=ldb,1920x1080M@60,if=RGB666', then saveenv and reset.

I saw the log from concole is "ldb ldb.14: failed to find valid LVDS channel".

The HDMI output can work normally. In the uboot, it shows:

U-Boot 2016.03-20415-ged95621 (Jul 07 2016 - 17:28:42 -0700), Build: jenkins-ub4

CPU: Freescale i.MX6Q rev1.2 at 792 MHz

Reset cause: POR

Board: SABRE Lite

I2C: ready

DRAM: 1 GiB

MMC: FSL_SDHC: 0, FSL_SDHC: 1

SF: Detected SST25VF016B with page size 256 Bytes, erase size 4 KiB, total 2 MiB

auto-detected panel 1280x720M@60

Display: hdmi:1280x720M@60 (1280x720)

In: serial

Out: serial

Err: serial

Net: Micrel ksz9021 at 6

FEC [PRIME]

Error: FEC address not set.

, usb_ether

Hit any key to stop autoboot: 0

How can I change the default panel from HDMI to LVDS?

gary_bisson · ‎07-28-2016

Hi,

Please read our blog posts entirely. The image you are using comes from here:

https://boundarydevices.com/mx-linux-kernel-3-14-52/

At the end of the post it is said:

"

U-Boot is in charge of setting the display parameters in the device tree. So it requires to use U-Boot v2015.07 or higher. Please make sure to read our blog post about this release:

https://boundarydevices.com/compiling-latest-u-boot-for-i-mx6-2015-edition

"

Everything is explained there. Hope this helps.

Regards,

Gary

durmus · ‎07-27-2016

Hi,

What you changed is bootargs for Linux kernel and therefore Linux will try to use LVDS port as display. However what you show us is the output of u-boot and it does not have much to do with Linux display configuration.

You mention "ldb ldb.14: failed to find valid LVDS channel".

Are you sure LVDS port is configured correctly? Show us your device tree.

xiaochao0131 · ‎07-27-2016

Hi,

The uboot and Ubuntu image is downloaded from official website, I did not change anything yet, Do you mean I need to download the BSP sourcecode and modify the LVDS config file then rebuild BSP?

durmus · ‎07-28-2016

Hi,

If you want to change your U-boot default display, you should definitely modify U-boot source.

However, if you just want to change Ubuntu display, what you did seems correct to me. But because you are getting that ldb error, the only reason I can think of is that LVDS is not enabled in device tree.

What does the documentation say? LVDS enabled by default?

xiaochao0131 · ‎07-28-2016

I just want to change Ubuntu display, I saw the log in serial console shows that "LVDS disabled", how to enable LVDS? which document can be referenced for the issue?

durmus · ‎07-28-2016

You said that U-boot and Ubuntu image are downloaded from official website. Surely, there must be some documentation there?

If LVDS is disabled, you should either find a precompiled .dts file with LVDS enabled for your board or you should do that yourself. Download kernel source, enable LVDS in device tree, compile and deploy.

xiaochao0131 · ‎07-28-2016

BTW, I run printenv in u-boot, the log shows as below:

cmd_hdmi=fdt set fb_hdmi status okay;fdt set fb_hdmi mode_str 1280x720M@60;

cmd_lcd=fdt set fb_lcd status disabled

cmd_lvds=fdt set fb_lvds status disabled;fdt set ldb/lvds-channel@0 status disab

led

the lvds status is disabled, can I enable it in u-boot?

xiaochao0131 · ‎07-28-2016

When power on the board, I noticed that the backlight of LVDS panel flick some times.

xiaochao0131 · ‎07-28-2016

Below is the log:

U-Boot 2016.03-20415-ged95621 (Jul 07 2016 - 17:28:42 -0700), Build: jenkins-ub4

CPU: Freescale i.MX6Q rev1.2 at 792 MHz

Reset cause: POR

Board: SABRE Lite

I2C: ready

DRAM: 1 GiB

MMC: FSL_SDHC: 0, FSL_SDHC: 1

SF: Detected SST25VF016B with page size 256 Bytes, erase size 4 KiB, total 2 MiB

Display: hdmi:1280x720M@60 (1280x720)

In: serial

Out: serial

Err: serial

Net: Micrel ksz9021 at 6

FEC [PRIME]

Error: FEC address not set.

, usb_ether

Hit any key to stop autoboot: 0

AHCI 0001.0300 32 slots 1 ports 3 Gbps 0x1 impl SATA mode

flags: ncq stag pm led clo only pmp pio slum part

No port device detected!

** Bad device size - sata 0 **

SATA device 1: unknown device

** Bad device sata 1 **

MMC: no card present

** Bad device mmc 0 **

switch to partitions #0, OK

mmc1 is current device

4437 bytes read in 29 ms (149.4 KiB/s)

## Executing script at 10008000

** File not found uEnv.txt **

42869 bytes read in 1207 ms (34.2 KiB/s)

only CEA modes allowed on HDMI port

----------- trying to load /initrd.img

2317536 bytes read in 280 ms (7.9 MiB/s)

5499904 bytes read in 499 ms (10.5 MiB/s)

Kernel image @ 0x10800000 [ 0x000000 - 0x53ec00 ]

## Flattened Device Tree blob at 13000000

Booting using the fdt blob at 0x13000000

reserving fdt memory region: addr=13000000 size=b000

Using Device Tree in place at 13000000, end 1300dfff

Starting kernel ...

ldb ldb.14: failed to find valid LVDS channel

fec 2188000.ethernet (unregistered net_device): Invalid MAC address: 00:00:00:00

snvs_rtc 20cc034.snvs-rtc-lp: can't get snvs-rtc clock

imx6q-pcie 1ffc000.pcie: phy link never came up

imx6q-pcie 1ffc000.pcie: Failed to bring link up!

imx6q-pcie 1ffc000.pcie: failed to initialize host

ili210x_i2c 2-0041: i2c transfer failed

ili210x_i2c 2-0041: Failed to get firmware version, err: -5

tsc2004_reset: write_cmd -5

tsc2004 2-0048: Failed to reset TSC -5

adv7180 2-0020: adv7180_read:read reg error: reg=11 ret=-5

egalax_ts 2-0004: Failed to read firmware version

ft5x06-ts 2-0038: ft5x06: Could not detect touch screen -19.

tc358743_read_reg:reg=0 ret=-5

tc358743_probe:cannot find camera

tc358743_probe: failed, error=-19

ov5640_read_reg:write reg error:reg=300a

mxc_v4l_open: Mxc Camera no sensor ipu0/csi0

mxc_v4l_open: Mxc Camera no sensor ipu1/csi0

mxc_v4l_open: Mxc Camera no sensor ipu0/csi0

mxc_v4l_open: Mxc Camera no sensor ipu1/csi1

update_device_addr: ov5640_mipi ret=-5

ov5640_read_reg(mipi):reg=300a ret=-5

update_device_addr: ov5642 ret=-5

ov5642_read_reg:write reg error:reg=300a

[ OK ]

saned disabled; edit /etc/default/saned

Ubuntu 14.04.4 LTS nitrogen ttymxc1

How to set LVDS as default panel

How to set LVDS as default panel

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