Author: Francis Rowe <firstname.lastname@example.org>
Date: Mon, 19 Oct 2015 03:21:08 +0100
docs/hcl/gm45_lcd.html: Notes about LVDS dual/single auto-detect
1 file changed, 4 insertions(+), 14 deletions(-)
diff --git a/docs/hcl/gm45_lcd.html b/docs/hcl/gm45_lcd.html
@@ -44,25 +44,15 @@
- T500/R400 are clones of the T400. See <b>coreboot/src/mainboard/lenovo/t400/devicetree.cb</b> in libreboot,
- and note that <b>register "gfx.lvds_dual_channel" = "0"</b> - in other words, single channel LVDS mode is
- enforced. This works on the lower resolution panels (1280x800), but not on the higher ones.
- For the high-res panels, re-compiling with <b>register "gfx.lvds_dual_channel" = "1"</b> partially solves
- the problem for those displays; there is still no display in GRUB, but once the kernel takes over, there
- is a display.
- Linux (kernel) has its own init code (including EDID parsing). The current suspicion is that coreboot's
- own initialization code has buggy EDID parsing in some way, such that the proper settings for the panel
- are not used, leading to the failure. The actual graphics initialization does work.
+ 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.
The i915 module in the Linux kernel also provides an option to set the LVDS link configuration.
lvds_channel_mode:Specify LVDS channel mode (0=probe BIOS [default], 1=single-channel, 2=dual-channel) (int)
- - from /sbin/modinfo i915
+ - from /sbin/modinfo i915 - use <b>lvds_channel_mode=2</b> as a kernel option in grub.cfg.