gma skl: Disable DDI clocks on reset path

After reset DPLL_CTRL2 is initialized to 0. Which means some clock
disable bits are not set and might cause some hassle later. Set them
and close the related TODO.

Change-Id: I1a470dff55e317e8119906b3e397f6f2314abcbd
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/20648
Tested-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

TODO

@@ -4,6 +4,4 @@ unknown	DP	honor SINK_STATUS after training
 
 low	LVDS	8bit colors, data format???
 
-medium  SKL     check if DPLL_CTRL2 really defaults to `Clock Off` => 0
-
 medium  gfxtest take care of our own framebuffer mapping

common/haswell_shared/hw-gfx-gma-connectors-ddi.adb

@@ -747,4 +747,18 @@ package body HW.GFX.GMA.Connectors.DDI is
       end if;
    end Off;
 
+   ----------------------------------------------------------------------------
+
+   procedure Post_Reset_Off
+   is
+      Clocks_Off : Word32 := 0;
+   begin
+      if not Config.Has_Per_DDI_Clock_Sel and not Config.Has_DDI_PHYs then
+         for Port in Digital_Port loop
+            Clocks_Off := Clocks_Off or DPLL_CTRL2_DDIx_CLOCK_OFF (Port);
+         end loop;
+         Registers.Set_Mask (Registers.DPLL_CTRL2, Clocks_Off);
+      end if;
+   end Post_Reset_Off;
+
 end HW.GFX.GMA.Connectors.DDI;

common/haswell_shared/hw-gfx-gma-connectors-ddi.ads

@@ -28,6 +28,8 @@ is
 
    procedure Off (Port : Digital_Port);
 
+   procedure Post_Reset_Off;
+
 private
    type Buf_Trans_Range is range 0 .. 19;
    type Buf_Trans_Array is array (Buf_Trans_Range) of Word32;

common/haswell_shared/hw-gfx-gma-connectors.adb

@@ -21,6 +21,12 @@ with GNAT.Source_Info;
 
 package body HW.GFX.GMA.Connectors is
 
+   procedure Post_Reset_Off
+   is
+   begin
+      DDI.Post_Reset_Off;
+   end Post_Reset_Off;
+
    procedure Initialize
    is
    begin

common/hw-gfx-gma-connectors.ads

@@ -14,10 +14,11 @@
 
 private package HW.GFX.GMA.Connectors is
 
-   pragma Warnings (GNATprove, Off, "subprogram ""Initialize"" has no effect",
+   pragma Warnings (GNATprove, Off, "subprogram ""*"" has no effect",
                     Reason => "Only effects some platforms");
+   procedure Post_Reset_Off;
    procedure Initialize;
-   pragma Warnings (GNATprove, On, "subprogram ""Initialize"" has no effect");
+   pragma Warnings (GNATprove, On, "subprogram ""*"" has no effect");
 
    pragma Warnings (GNATprove, Off, "unused variable ""P*""",
                     Reason => "Needed for a common interface");

common/hw-gfx-gma.adb

@@ -408,8 +408,10 @@ is
          Registers.Clear_Fences;
       else
          -- According to PRMs, VGA plane is the only thing
-         -- that's enabled by default after reset.
+         -- that's enabled by default after reset...
          Display_Controller.Legacy_VGA_Off;
+         -- ... along with some DDI port bits since Skylake.
+         Connectors.Post_Reset_Off;
       end if;
 
       -------------------- Now restart from a clean state ---------------------

common/ironlake/hw-gfx-gma-connectors.adb

@@ -29,11 +29,8 @@ with GNAT.Source_Info;
 package body HW.GFX.GMA.Connectors
 is
 
-   procedure Initialize
-   is
-   begin
-      null;
-   end Initialize;
+   procedure Post_Reset_Off is null;
+   procedure Initialize is null;
 
    function Is_Internal (Port_Cfg : Port_Config) return Boolean
    is