Hi James - On Fri, 01 Mar 2013, James Courtier-Dutton <james.dutton at gmail.com> wrote: >> James, try to revert that commit. Does it fix? >> >> If so, you should check the output of intel_reg_dumper at broken and >> working states. >> > Can someone point me to a datasheet that relates to this bit of code, so i > can understand what all the registers do. > I would like to understand the code in order to suggest a better fix. https://01.org/linuxgraphics/documentation/driver-documentation-prms Vol 3 is the relevant volume in each generation. I don't think any of the docs back up the comments in the bad commit saying "BLC_PWM_CPU_CTL is cleared to zero automatically when BLC_PWM_CPU_CTL2 and BLC_PWM_PCH_CTL1 are written" though. I guess it could be some bad ACPI/BIOS interaction too. I'd still urge you to file the bug, and attach the dmesgs and register dumps first. And let us know if the revert fixes it. BR, Jani.
