[Bug 97363] [drm:ironlake_crtc_compute_clock [i915]] *ERROR* Couldn't find PLL settings for mode!

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=97363

--- Comment #2 from Robin Müller <rm1990 at gmx.de> ---
I added some logging to the intel_display.c for both linux-4.6 and linux-4.7.
While running these customized kernels I figured out the following:
In both cases the same methods are called. So my first assumption was wrong,
that in linux-4.6 maybe a different method then g4x_find_best_dpll was used for
calculating the PLL. But I found a difference in the values passed to this
method. The value of the parameter target is 100400 using linux-4.6 and 25180
using linux-4.7. As the code of the method g4x_find_best_dpll hasn't changed
between these 2 versions, I'd say the different input value causes the bug.
At the moment I haven't found the location where the value for target
(crtc_state->port_clock) comes from but it's not that easy navigating through
the code just using vim. If I find some time tomorrow I'll try how well
IntelliJ can handle C projects to find the cause for the different values for
the crtc_state->port_clock
Furthermore I hope this information is useful for somebody else to dig into
this issue.

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