tree 8a84cb4ae9f3f8384e233c61eeb1de6c32b3d423
parent 07ff1b95bb1db12cc3d01e3f542338d25eb2dbf3
author Nico Huber <nico.h@gmx.de> 1569708441 +0200
committer Nico Huber <nico.h@gmx.de> 1571401156 +0000

gma g45: Read CDClk and calculate dot-clock limits

Numbers are taken from `intel_cdclk.c` of Linux' i915 driver.

We introduce three new procedures to the `Power_And_Clocks` interface:

  o Limit_Dotclocks() limits the dot clocks of all pipe configs
    according to the maximum supported CDClk. It also reports if
    CDClk has to be switched for these configs.

  o Update_CDClk() performs the CDClk switch if necessary. It may
    further limit the dot clocks if the switch didn't succeed.

  o Enable_CDClk() ensures that the CDClk is running. This may be
    necessary to probe for DP displays when no pipes are active.

The latter two are no-ops for G45, as the CDClk runs at a fixed rate.
Dot clocks are limited to 90% of CDClk.

Change-Id: Ie50c0f8f51b3a0a6ed58c6461069c556cc92f51e
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/libgfxinit/+/35715
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>