[PATCH 29/45] drm/amd/display: Use 100 Hz precision for pipe pixel clocks

[Chalmers, Kenneth]

> > From: Ken Chalmers <ken.chalmers at amd.com>
> >
> > [Why]
> > Users would like more accurate pixel clocks, especially for fractional
> > "TV" frame rates like 59.94 Hz.
> >
> > [How]
> > Store and communicate pixel clocks with 100 Hz accuracy from
> > dc_crtc_timing through to BIOS command table setpixelclock call.
> 
> Why not directly use Hz?
> 
> I mean we don't have any pixel clocks above 4GHz, don't we? So a 32bit
> integer should be a perfect fit.
> 
> Christian.

Currently the VBIOS only supports 100 Hz precision, so there's no immediate 
benefit to moving to greater than 100 Hz precision.

Even so, using Hz directly was actually discussed during development, but 
the summary from an architect was:

> I agree long term HZ is better.  Pixel clock value will fit within
> 32bit, but we have many calculation based on pixel clock and changing
> to HZ will require bigger effort to make sure the math (there are places
> we multiple pixel clock) doesn’t overflow 32bit integer.  100hz is a 
> compromised short term solution.

    -Ken