[Bug 87682] Horizontal lines in radeon driver on kernel 3.15 and upwards

https://bugs.freedesktop.org/show_bug.cgi?id=87682

--- Comment #17 from Chris Bainbridge chris.bainbridge@gmail.com --- Christian König posted an explanation of the PLL divider values at https://bugzilla.kernel.org/show_bug.cgi?id=91861#c12 (another "no screen after 3.15" bug report)

The various fixes adjust the divider value limits slightly for different displays. The basic formula is commented in the radeon_compute_pll_avivo function:

dot_clock = (ref_freq * feedback_div) / (ref_div * post_div)

So by adjusting the limits of those values you can find something that works for your laptop display. But I don't know which solution is technically correct - if you don't get a reply here you could try emailing Christian König and asking.