[Bug 77009] 24P playback video signal loss with latest DRI patches

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=77009

--- Comment #24 from Christian König <deathsimple at vodafone.de> ---
(In reply to comment #22)
> I am trying to understand the plls.

Well how deep are you interested in getting into this? PLLs can be complicated,
but are also one of the very basic building blocks of electronics.

> I read the org. bug report 76564.  I
> assumed increasing the max would allow higher pll vals.  But it does go down
> with some.  Does that make sense?  

More or less yes. See your numbers for example, without the limit patch you had
the params like this:

148340 - 14834, pll dividers - fb: 741.7 ref: 50, post 10

This means with a feedback divider of 741.7, a referenz divider of 50 and a
post divider of 10 you have an exact match for the frequency.

There is just the little problem that as the divider numbers get higher the
signal gets more unstable. So in reality you don't get 148.340 MHz, but instead
something that fluctuates between 148.339 MHz and 148.341 MHz (for example).

The overall match for the average frequency is still better than with lower
numbers, but your TV/Monitor can't deal with such high fluctuations in it.

> Your patch does wonders for this A4-3400.  I am trying to understand it
> better.
> 
> Here your max is 100.  ref: 10, post 10  >>>> 10 * 10 = 100 max.

Yes correct.

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