<html> <head> <base href="https://bugs.freedesktop.org/" /> </head> <body> <div> <a class="bz_bug_link bz_status_NEEDINFO " title="NEEDINFO --- - [i945GM regression] in 3.7.0 kernel on macbook1,1 (kernel crash)" href="https://bugs.freedesktop.org/show_bug.cgi?id=58396#c26">Comment # 26</a> on <a class="bz_bug_link bz_status_NEEDINFO " title="NEEDINFO --- - [i945GM regression] in 3.7.0 kernel on macbook1,1 (kernel crash)" href="https://bugs.freedesktop.org/show_bug.cgi?id=58396">bug 58396</a> from <a class="email" href="mailto:peter.ujfalusi@gmail.com" title="Peter Ujfalusi <peter.ujfalusi@gmail.com>"> Peter Ujfalusi</a> <pre>(In reply to <a href="show_bug.cgi?id=58396#c25">comment #25</a>) > I'll submit it with the bug link updated asap for 3.8, if it passes > review and all, it should land in a stable backport in 1-2 weeks. But > holidays might delay that a bit. Cool, thanks. > > Out of curiosity: do you have short explanation on why this patch actually > > helps/works? > > Your BIOS enables VGA on the same pipe 1 as it enables LVDS. When > setting up the initial kms config we go through all pipes: First we > disable pipe 0, since it's unused, then we'll enable the desired > config for LVDS on pipe 1. > > The problem now is that for historical reasons the new i915 modeset > code disables any outputs when they're disconnected for _any_ modeset, > i.e. when we ensure that pipe 0 is off, it also wants to disable VGA > out on pipe 0. Imo this is braindead semantics, but it's bug-for-bug > compatible with the old modeset implementation from 3.6. The problem > now is that the new modeset always enables/disables the entire pipe, > so to disable VGA on pipe it needs to enable/disable LVDS on pipe 1, > too. There we fall over, since at we don't (yet) read out the mode set > up by the BIOS, hence the NULL deref oops. I see. Thank you for taking the time to explain it. It does make perfect sense. It would have taken a bit of time if I started to read the code and the debug messages to come to this conclusion (I'm an ASoC guy)... Thanks again! Peter</pre> </div> <hr> You are receiving this mail because: <ul> <li>You are the QA Contact for the bug.</li> <li>You are the assignee for the bug.</li> </ul> </body> </html>