https://bugs.freedesktop.org/show_bug.cgi?id=17902

--- Comment #63 from Gilles Dartiguelongue gilles.dartiguelongue@esiee.org 2012-04-15 08:56:35 PDT --- For the record, I'm still working on this from time to time. I ported the patch to kernel land quite easily, but still can't figure out what is the problem with register read failures.

Example from a 3.3.1 kernel booted with i915.modeset=1 drm.debug=0x04:

Apr 15 17:52:11 mobilix kernel: [drm:ns2501_init], init ns2501 dvo controller successfully! Apr 15 17:52:11 mobilix kernel: [drm:ns2501_readb], Unable to read register 0x08 from i915 gmbus dpb:38. Apr 15 17:52:11 mobilix kernel: [drm:ns2501_readb], Unable to read register 0x08 from i915 gmbus dpb:38. Apr 15 17:52:11 mobilix kernel: [drm:ns2501_readb], Unable to read register 0x08 from i915 gmbus dpb:38. Apr 15 17:52:11 mobilix kernel: [drm:ns2501_readb], Unable to read register 0x09 from i915 gmbus dpb:38. Apr 15 17:52:11 mobilix kernel: [drm:ns2501_readb], Unable to read register 0x08 from i915 gmbus dpb:38.

I would really appreciate someone with drm/intel knowledge helping here. Will post patches later (code is really not that different that my previous post about this).