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

[bugzilla-daemon at bugzilla.kernel.org]

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

--- Comment #6 from Mike S. <michael.selig at fs.com.au> ---
I can confirm that the patch
https://bugzilla.kernel.org/attachment.cgi?id=163891 to cap ref_div to 7 fixes
the problem on my RS780. I did the test on kernel 3.18.3. Note that I also cast
the number 7 in the min() to unsigned to avoid a compiler warning.

I'd like to run it for a few days to ensure that it is stable.

I'd also like to ask a question, please. With this patch, the GPU divider
values are now running at:

148500 - 148490, pll dividers - fb: 580.7 ref: 7, post 8

while on 3.14 they were:

14851, pll dividers - fb: 145.2 ref: 2, post: 7

These new values produce a marginally different dot clock rate (the old debug
msg displayed the value 10x less than the new one), but the difference is tiny,
and probably doesn't make any practical difference.

Other than the dot clock, do the values of the 3 dividers affect anything else
in the GPU? Are there any advantages or disadvantages running the FB and REF
substantially higher (as they are now)?

Thank you!

-- 
You are receiving this mail because:
You are watching the assignee of the bug.