Troubleshooting LVDS on GM45 (kernel 4.5.0)

[Rob Kramer]

I've tried again without video parameter -- same outcome. I've also 
applied Ville's patch "drm/i915: Read timings from the correct 
transcoder in intel_crtc_mode_get()" (with teeny backport fix). It seems 
this code is never called in my case though, since intel_lvds_init() 
chooses to use the VBT mode instead. Log is uploaded here: 
http://pastebin.com/bGa2UvLu

Since this VBT mode is probably junk anyway, I commented out the 
if-statement that selects it (in intel_lvds.c), so that the code will 
pick the mode as set by BIOS. The result is much better, I actually get 
proper looking output! X also runs well on top of that.

There are still several errors in the log file though (probably caused 
by my little hack), see here: http://pastebin.com/UbCjizSV.

Is using the mode as set up by BIOS the way to go for LVDS? If so, is 
there a module parameter that can force this, or force the bogus VBT to 
be disregarded?

Cheers!

       Rob


On 04/01/2016 07:11 PM, Jani Nikula wrote:
>
> Apr  1 11:32:21 vides user.err kernel: [    4.896341] [drm:i9xx_crtc_compute_clock [i915]] *ERROR* Couldn't find PLL settings for mode!
>
> Please try without the kernel command line mode.
>
> BR,
> Jani.
>