# LCD compatibility on GM45 laptops

On the T400 and T500 (maybe others), some of the higher resolution panels (e.g. 1440x900, 1680x1050, 1920x1200) fail in libreboot.

All X200/X200S/X200T LCD panels are believed to be compatible.

Back to previous index.

# The problem

In some cases, backlight turns on during boot, sometimes not. In all cases, no display is shown in GRUB, nor in GNU/Linux.

# Current workaround:

Libreboot (git, and releases after 20150518) now automatically detect whether to use single or dual link LVDS configuration. If you're using an older version, use the instructions below. In practise, this means that you'll get a visual display when booting GNU/Linux, but not in GRUB (payload).

The i915 module in the Linux kernel also provides an option to set the LVDS link configuration. i915.lvds_channel_mode:Specify LVDS channel mode (0=probe BIOS [default], 1=single-channel, 2=dual-channel) (int) - from /sbin/modinfo i915 - use i915.lvds_channel_mode=2 as a kernel option in grub.cfg.

# Differences in dmesg (kernel parameter added: )

https://01.org/linuxgraphics/documentation/how-report-bugs

These panels all work in the original firmware, so the idea is to see what differences there are in how coreboot handles them.

dmesg with coreboot-libre (coreboot) - See: [drm:intel_lvds_init] detected single-link lvds configuration

dmesg with lenovobios (lenovobios) - For the same line, it says dual-channel lvds configuration.

## EDID

One T500 had a screen (1920x1200) that is currently incompatible. Working to fix it. EDID:

    user@user-ThinkPad-T500:~/Desktop$ sudo i2cdump -y 2 0x50
    No size specified (using byte-data access)
         0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f    0123456789abcdef
    00: XX ff ff ff ff ff ff 00 30 ae 55 40 00 00 00 00    X.......0?U@....
    10: 00 11 01 03 80 21 15 78 ea ba 70 98 59 52 8c 28    .????!?x??p?YR?(
    20: 25 50 54 00 00 00 01 01 01 01 01 01 01 01 01 01    %PT...??????????
    30: 01 01 01 01 01 01 e7 3a 80 8c 70 b0 14 40 1e 50    ???????:??p??@?P
    40: 24 00 4b cf 10 00 00 19 16 31 80 8c 70 b0 14 40    $.K??..??1??p??@
    50: 1e 50 24 00 4b cf 10 00 00 19 00 00 00 0f 00 d1    ?P$.K??..?...?.?
    60: 0a 32 d1 0a 28 11 01 00 32 0c 00 00 00 00 00 fe    ?2??(??.2?.....?
    70: 00 4c 50 31 35 34 57 55 31 2d 54 4c 42 31 00 9a    .LP154WU1-TLB1.?
    80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
    90: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
    a0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
    b0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
    c0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
    d0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
    e0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
    f0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................

What happens: backlight turns on at boot, then turns off. At no point is there a working visual display.

Another incompatible screen (EDID) 1680 x 1050 with the same issue:

    EDID:
    00 ff ff ff ff ff ff 00 30 ae 53 40 00 00 00 00
    00 11 01 03 80 21 15 78 ea cd 75 91 55 4f 8b 26
    21 50 54 00 00 00 01 01 01 01 01 01 01 01 01 01
    01 01 01 01 01 01 a8 2f 90 e0 60 1a 10 40 20 40
    13 00 4b cf 10 00 00 19 b7 27 90 e0 60 1a 10 40
    20 40 13 00 4b cf 10 00 00 19 00 00 00 0f 00 b3
    0a 32 b3 0a 28 14 01 00 4c a3 50 33 00 00 00 fe
    00 4c 54 4e 31 35 34 50 33 2d 4c 30 32 0a 00 7e
    Extracted contents:
    header:          00 ff ff ff ff ff ff 00
    serial number:   30 ae 53 40 00 00 00 00 00 11
    version:         01 03
    basic params:    80 21 15 78 ea
    chroma info:     cd 75 91 55 4f 8b 26 21 50 54
    established:     00 00 00
    standard:        01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01
    descriptor 1:    a8 2f 90 e0 60 1a 10 40 20 40 13 00 4b cf 10 00 00 19
    descriptor 2:    b7 27 90 e0 60 1a 10 40 20 40 13 00 4b cf 10 00 00 19
    descriptor 3:    00 00 00 0f 00 b3 0a 32 b3 0a 28 14 01 00 4c a3 50 33
    descriptor 4:    00 00 00 fe 00 4c 54 4e 31 35 34 50 33 2d 4c 30 32 0a
    extensions:      00
    checksum:        7e

    Manufacturer: LEN Model 4053 Serial Number 0
    Made week 0 of 2007
    EDID version: 1.3
    Digital display
    Maximum image size: 33 cm x 21 cm
    Gamma: 220%
    Check DPMS levels
    DPMS levels: Standby Suspend Off
    Supported color formats: RGB 4:4:4, YCrCb 4:2:2
    First detailed timing is preferred timing
    Established timings supported:
    Standard timings supported:
    Detailed timings
    Hex of detail: a82f90e0601a1040204013004bcf10000019
    Did detailed timing
    Detailed mode (IN HEX): Clock 122000 KHz, 14b mm x cf mm
                   0690 06b0 06f0 0770 hborder 0
                   041a 041b 041e 042a vborder 0
                   -hsync -vsync
    Hex of detail: b72790e0601a1040204013004bcf10000019
    Detailed mode (IN HEX): Clock 122000 KHz, 14b mm x cf mm
                   0690 06b0 06f0 0770 hborder 0
                   041a 041b 041e 042a vborder 0
                   -hsync -vsync
    Hex of detail: 0000000f00b30a32b30a281401004ca35033
    Manufacturer-specified data, tag 15
    Hex of detail: 000000fe004c544e31353450332d4c30320a
    ASCII string: LTN154P3-L02
    Checksum
    Checksum: 0x7e (valid)
    WARNING: EDID block does NOT fully conform to EDID 1.3.
            Missing name descriptor
            Missing monitor ranges
    bringing up panel at resolution 1680 x 1050
    Borders 0 x 0
    Blank 224 x 16
    Sync 64 x 3
    Front porch 32 x 1
    Spread spectrum clock
    Single channel
    Polarities 1, 1
    Data M1=2132104, N1=8388608
    Link frequency 270000 kHz
    Link M1=236900, N1=524288
    Pixel N=9, M1=24, M2=8, P1=1
    Pixel clock 243809 kHz
    waiting for panel powerup
    panel powered up

Another incompatible (T400) screen:

    No size specified (using byte-data access)
         0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f    0123456789abcdef
    00: XX ff ff ff ff ff ff 00 30 ae 33 40 00 00 00 00    X.......0?3@....
    10: 00 0f 01 03 80 1e 13 78 ea cd 75 91 55 4f 8b 26    .??????x??u?UO?&
    20: 21 50 54 00 00 00 01 01 01 01 01 01 01 01 01 01    !PT...??????????
    30: 01 01 01 01 01 01 b0 27 a0 60 51 84 2d 30 30 20    ???????'?`Q?-00
    40: 36 00 2f be 10 00 00 19 d5 1f a0 40 51 84 1a 30    6./??..????@Q??0
    50: 30 20 36 00 2f be 10 00 00 19 00 00 00 0f 00 90    0 6./??..?...?.?
    60: 0a 32 90 0a 28 14 01 00 4c a3 42 44 00 00 00 fe    ?2??(??.L?BD...?
    70: 00 4c 54 4e 31 34 31 57 44 2d 4c 30 35 0a 00 32    .LTN141WD-L05?.2
    80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
    90: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
    a0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
    b0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
    c0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
    d0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
    e0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
    f0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................

For comparison, here is a working display (T400 screen, but was connected to a T500. Some T500 displays also work, but no EDID available on this page yet):

    EDID:
    00 ff ff ff ff ff ff 00 30 ae 31 40 00 00 00 00
    00 12 01 03 80 1e 13 78 ea b3 85 95 58 53 8a 28
    25 50 54 00 00 00 01 01 01 01 01 01 01 01 01 01
    01 01 01 01 01 01 26 1b 00 7d 50 20 16 30 30 20
    36 00 30 be 10 00 00 18 8b 16 00 7d 50 20 16 30
    30 20 36 00 30 be 10 00 00 18 00 00 00 0f 00 81
    0a 32 81 0a 28 14 01 00 30 e4 28 01 00 00 00 fe
    00 4c 50 31 34 31 57 58 33 2d 54 4c 52 31 00 d8
    Extracted contents:
    header:          00 ff ff ff ff ff ff 00
    serial number:   30 ae 31 40 00 00 00 00 00 12
    version:         01 03
    basic params:    80 1e 13 78 ea
    chroma info:     b3 85 95 58 53 8a 28 25 50 54
    established:     00 00 00
    standard:        01 01 01 01 01 01 01 01 01 01 01 01 01 01 01 01
    descriptor 1:    26 1b 00 7d 50 20 16 30 30 20 36 00 30 be 10 00 00 18
    descriptor 2:    8b 16 00 7d 50 20 16 30 30 20 36 00 30 be 10 00 00 18
    descriptor 3:    00 00 00 0f 00 81 0a 32 81 0a 28 14 01 00 30 e4 28 01
    descriptor 4:    00 00 00 fe 00 4c 50 31 34 31 57 58 33 2d 54 4c 52 31
    extensions:      00
    checksum:        d8

    Manufacturer: LEN Model 4031 Serial Number 0
    Made week 0 of 2008
    EDID version: 1.3
    Digital display
    Maximum image size: 30 cm x 19 cm
    Gamma: 220%
    Check DPMS levels
    DPMS levels: Standby Suspend Off
    Supported color formats: RGB 4:4:4, YCrCb 4:2:2
    First detailed timing is preferred timing
    Established timings supported:
    Standard timings supported:
    Detailed timings
    Hex of detail: 261b007d502016303020360030be10000018
    Did detailed timing
    Detailed mode (IN HEX): Clock 69500 KHz, 130 mm x be mm
                   0500 0530 0550 057d hborder 0
                   0320 0323 0329 0336 vborder 0
                   -hsync -vsync
    Hex of detail: 8b16007d502016303020360030be10000018
    Detailed mode (IN HEX): Clock 69500 KHz, 130 mm x be mm
                   0500 0530 0550 057d hborder 0
                   0320 0323 0329 0336 vborder 0
                   -hsync -vsync
    Hex of detail: 0000000f00810a32810a2814010030e42801
    Manufacturer-specified data, tag 15
    Hex of detail: 000000fe004c503134315758332d544c5231
    ASCII string: LP141WX3-TLR1
    Checksum
    Checksum: 0xd8 (valid)
    WARNING: EDID block does NOT fully conform to EDID 1.3.
            Missing name descriptor
            Missing monitor ranges
    bringing up panel at resolution 1280 x 800
    Borders 0 x 0
    Blank 125 x 22
    Sync 32 x 6
    Front porch 48 x 3
    Spread spectrum clock
    Single channel
    Polarities 1, 1
    Data M1=1214600, N1=8388608
    Link frequency 270000 kHz
    Link M1=134955, N1=524288
    Pixel N=10, M1=14, M2=11, P1=1
    Pixel clock 138857 kHz
    waiting for panel powerup
    panel powered up

Another compatible T400 screen:

    trisquel@trisquel:~$ sudo i2cdump -y 2 0x50
    No size specified (using byte-data access)
         0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f    0123456789abcdef
    00: 00 ff ff ff ff ff ff 00 30 ae 31 40 00 00 00 00    ........0?1@....
    10: 00 12 01 03 80 1e 13 78 ea b3 85 95 58 53 8a 28    .??????x????XS?(
    20: 25 50 54 00 00 00 01 01 01 01 01 01 01 01 01 01    %PT...??????????
    30: 01 01 01 01 01 01 26 1b 00 7d 50 20 16 30 30 20    ??????&?.}P ?00
    40: 36 00 30 be 10 00 00 18 8b 16 00 7d 50 20 16 30    6.0??..???.}P ?0
    50: 30 20 36 00 30 be 10 00 00 18 00 00 00 0f 00 81    0 6.0??..?...?.?
    60: 0a 32 81 0a 28 14 01 00 30 e4 28 01 00 00 00 fe    ?2??(??.0?(?...?
    70: 00 4c 50 31 34 31 57 58 33 2d 54 4c 52 31 00 d8    .LP141WX3-TLR1.?
    80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
    90: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
    a0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
    b0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
    c0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
    d0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
    e0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................
    f0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff    ................

Copyright © 2015 Leah Rowe <info@minifree.org>
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license can be found at ../gfdl-1.3.txt

Updated versions of the license (when available) can be found at https://www.gnu.org/licenses/licenses.html

UNLESS OTHERWISE SEPARATELY UNDERTAKEN BY THE LICENSOR, TO THE EXTENT POSSIBLE, THE LICENSOR OFFERS THE LICENSED MATERIAL AS-IS AND AS-AVAILABLE, AND MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND CONCERNING THE LICENSED MATERIAL, WHETHER EXPRESS, IMPLIED, STATUTORY, OR OTHER. THIS INCLUDES, WITHOUT LIMITATION, WARRANTIES OF TITLE, MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, NON-INFRINGEMENT, ABSENCE OF LATENT OR OTHER DEFECTS, ACCURACY, OR THE PRESENCE OR ABSENCE OF ERRORS, WHETHER OR NOT KNOWN OR DISCOVERABLE. WHERE DISCLAIMERS OF WARRANTIES ARE NOT ALLOWED IN FULL OR IN PART, THIS DISCLAIMER MAY NOT APPLY TO YOU.

TO THE EXTENT POSSIBLE, IN NO EVENT WILL THE LICENSOR BE LIABLE TO YOU ON ANY LEGAL THEORY (INCLUDING, WITHOUT LIMITATION, NEGLIGENCE) OR OTHERWISE FOR ANY DIRECT, SPECIAL, INDIRECT, INCIDENTAL, CONSEQUENTIAL, PUNITIVE, EXEMPLARY, OR OTHER LOSSES, COSTS, EXPENSES, OR DAMAGES ARISING OUT OF THIS PUBLIC LICENSE OR USE OF THE LICENSED MATERIAL, EVEN IF THE LICENSOR HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH LOSSES, COSTS, EXPENSES, OR DAMAGES. WHERE A LIMITATION OF LIABILITY IS NOT ALLOWED IN FULL OR IN PART, THIS LIMITATION MAY NOT APPLY TO YOU.

The disclaimer of warranties and limitation of liability provided above shall be interpreted in a manner that, to the extent possible, most closely approximates an absolute disclaimer and waiver of all liability.