[Bug 91861] [Radeon RS780] Blank screen (no signal) on HDMI after boot in 3.15 & later

[bugzilla-daemon@bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=91861

--- Comment #13 from Mike S. <michael.selig@fs.com.au> ---
Wow, thank you very much for the detailed explanation :-)

Though all I was really expecting was a "yes/no or not sure" answer to  whether
the new higher values of fb_dev & ref_div on my RS780 could be responsible for
pushing the PLL "closer to the edge" than with the driver on kernel 3.14, and
therefore maybe less stable and/or produce more heat.

So, from your explanation, using a ref_div of 7 compared to 2, means that the
VCO is running at a higher frequency, and hence, higher voltage. So I assume
that would mean the GPU would be drawing more power & therefore run hotter,
though I am not sure how significant this is to its overall power use.

Is that right?

The reason I would like to know this is to determine whether the new divider
numbers would cause the GPU to be less stable & hotter, which is fairly
important in a HTPC where I am trying to keep fan noise to a minimum. If so, I
might then try to force the ref_div below 7 in the driver (as I know it has
been stable for several years at 2).

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