[coreboot-gerrit] Change in libgfxinit[master]: gma config: Allow to cache CDClk in variable config state

[Nico Huber (Code Review)]

Hello Arthur Heymans, Matt DeVillier, Thomas Heijligen,

I'd like you to do a code review. Please visit

https://review.coreboot.org/c/libgfxinit/+/35714

to review the following change.

Change subject: gma config: Allow to cache CDClk in variable config state
......................................................................

gma config: Allow to cache CDClk in variable config state

Add `CDClk` and `Max_CDClk` fields to the variable config state.
They will be used to cache the current hardware state, so that
we don't have to poke registers in every call to Update_Outputs().

Also introduce `CDClk_Range`, which is chosen such that common
dot-clock limits (90% of CDClk) are in range of `Frequency_Type`.

Change-Id: I3d9c956eabcedb2f8299a1642ff0172cd7f54e45
Signed-off-by: Nico Huber 
---
M common/hw-gfx-gma-config.ads.template
M common/hw-gfx-gma.ads
2 files changed, 15 insertions(+), 2 deletions(-)

git pull ssh://review.coreboot.org:29418/libgfxinit refs/changes/14/35714/1

diff --git a/common/hw-gfx-gma-config.ads.template b/common/hw-gfx-gma-config.ads.template
index d5bd2ba..bbfdc05 100644
--- a/common/hw-gfx-gma-config.ads.template
+++ b/common/hw-gfx-gma-config.ads.template
@@ -60,6 +60,8 @@
    type Valid_Port_Array is array (Port_Type) of Boolean;
    type Variable_Config is record
       Valid_Port     : Valid_Port_Array;
+      CDClk          : CDClk_Range;
+      Max_CDClk      : CDClk_Range;
       Raw_Clock      : Frequency_Type;
       Dyn_CPU        : Gen_CPU_Type;
       Dyn_CPU_Var    : Gen_CPU_Variant;
@@ -67,6 +69,8 @@

Initial_Settings : constant Variable_Config :=
      (Valid_Port     => (others => False),
+      CDClk          => CDClk_Range'First,
+      Max_CDClk      => CDClk_Range'First,
       Raw_Clock      => Frequency_Type'First,
       Dyn_CPU        => Gen_CPU_Type'First,
       Dyn_CPU_Var    => Gen_CPU_Variant'First);
@@ -74,6 +78,8 @@
    Variable : Variable_Config with Part_Of => GMA.State;

Valid_Port  : Valid_Port_Array renames Variable.Valid_Port;
+   CDClk       : CDClk_Range renames Variable.CDClk;
+   Max_CDClk   : CDClk_Range renames Variable.Max_CDClk;
    Raw_Clock   : Frequency_Type renames Variable.Raw_Clock;
    CPU         : Gen_CPU_Type renames Variable.Dyn_CPU;
    CPU_Var     : Gen_CPU_Variant renames Variable.Dyn_CPU_Var;
@@ -271,7 +277,7 @@

----------------------------------------------------------------------------

-   Default_CDClk_Freq : <ilkhswvar> Frequency_Type :=
+   Default_CDClk_Freq : <ilkhswvar> CDClk_Range :=
      (if    Gen_G45                          then 320_000_000  -- unused
       elsif CPU_Ironlake                     then 450_000_000
       elsif CPU_Sandybridge or CPU_Ivybridge then 400_000_000
@@ -279,7 +285,7 @@
       elsif Gen_Haswell                      then 450_000_000
       elsif Gen_Broxton                      then 288_000_000
       elsif Gen_Skylake                      then 337_500_000
-                                             else Frequency_Type'First);
+                                             else CDClk_Range'First);

Default_RawClk_Freq : <hswvar> Frequency_Type :=
      (if    Gen_G45        then 100_000_000  -- unused, depends on FSB
diff --git a/common/hw-gfx-gma.ads b/common/hw-gfx-gma.ads
index bdc4704..69df07d 100644
--- a/common/hw-gfx-gma.ads
+++ b/common/hw-gfx-gma.ads
@@ -206,6 +206,13 @@

private

+   -- Older Generations only allow dot clocks <= 90% of the CDClk.
+   -- Hence, to calculate the limit, CDClk must start higher.
+   subtype CDClk_Range is Frequency_Type
+      range Frequency_Type'First * 10 / 9 + 1 .. Frequency_Type'Last;
+
+   ----------------------------------------------------------------------------
+
    PCI_Usable : Boolean with Part_Of => State;
    use type HW.PCI.Index;
    procedure PCI_Read16 (Value : out Word16; Offset : HW.PCI.Index)