gma: Add Intel i945 (Gen3) graphics init support
Add i945G (desktop) and i945GM (mobile) generation support, modeled
after the existing G45 generation code with hardware-specific
adaptations based on the Linux i915 DRM driver and coreboot.
Key hardware differences from G45 (Gen4):
- GTT on separate PCI BAR3 (not within BAR0)
- Simple 32-bit GTT PTEs (addr[31:12] | valid[0])
- No DSPSURF register (uses DSPADDR/DSPLINOFF instead)
- Gen3 fence registers: 32-bit at split 0x2000/0x3000 addresses
- Different PLL limits (VCO 1400-2800 MHz, 96 MHz refclk)
- SDVO multiplier in DPLL register bits[7:4]
- LVDS restricted to Pipe B (pre-i965 requirement)
- CDClk: fixed 400 MHz (desktop) or GCFGC-based (mobile)
- No HDMI/DP, only VGA, LVDS, and SDVO outputs
- PCI IDs: 0x2772 (I945G), 0x27a2/0x27ae (I945GM)
TESTED with thinkpad x60: LVDS & VGA works with a linear framebuffer.
Change-Id: Ib67b3d0ee5e06df427869dce4db926ba57a80fd8
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.sourcearcade.org/c/libgfxinit/+/476
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Tested-by: Nico Huber <nico.h@gmx.de>
diff --git a/common/i945/hw-gfx-gma-port_detect.adb b/common/i945/hw-gfx-gma-port_detect.adb
new file mode 100644
index 0000000..af82c17
--- /dev/null
+++ b/common/i945/hw-gfx-gma-port_detect.adb
@@ -0,0 +1,68 @@
+--
+-- Copyright (C) 2026 Arthur Heymans <arthur@aheymans.xyz>
+--
+-- This program is free software; you can redistribute it and/or modify
+-- it under the terms of the GNU General Public License as published by
+-- the Free Software Foundation; either version 2 of the License, or
+-- (at your option) any later version.
+--
+-- This program is distributed in the hope that it will be useful,
+-- but WITHOUT ANY WARRANTY; without even the implied warranty of
+-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+-- GNU General Public License for more details.
+--
+
+with HW.GFX.GMA.Config;
+with HW.GFX.GMA.Registers;
+
+package body HW.GFX.GMA.Port_Detect
+is
+
+ CRT_HOTPLUG_INT_EN : constant := 1 * 2 ** 9;
+ CRT_HOTPLUG_ACTIVATION_PERIOD_64 : constant := 1 * 2 ** 8;
+
+ HOTPLUG_INT_STATUS : constant array (Active_Port_Type) of Word32 :=
+ (Analog => 1 * 2 ** 11,
+ others => 0);
+
+ procedure Initialize
+ is
+ begin
+ -- i945: VGA (ADPA) is always present
+ Config.Valid_Port (Analog) := True;
+
+ -- LVDS is only present on mobile (i945GM)
+ Config.Valid_Port (LVDS) := Config.GMCH_I945GM;
+
+ -- Enable CRT hotplug detection
+ Registers.Write
+ (Register => Registers.PORT_HOTPLUG_EN,
+ Value => CRT_HOTPLUG_INT_EN or CRT_HOTPLUG_ACTIVATION_PERIOD_64);
+ end Initialize;
+
+ procedure Hotplug_Detect (Port : in Active_Port_Type; Detected : out Boolean)
+ is
+ Ctl32 : Word32;
+ begin
+ Registers.Read (Register => Registers.PORT_HOTPLUG_STAT,
+ Value => Ctl32);
+ Detected := (Ctl32 and HOTPLUG_INT_STATUS (Port)) /= 0;
+
+ if Detected then
+ Registers.Set_Mask
+ (Register => Registers.PORT_HOTPLUG_STAT,
+ Mask => HOTPLUG_INT_STATUS (Port));
+ end if;
+ end Hotplug_Detect;
+
+ procedure Clear_Hotplug_Detect (Port : Active_Port_Type)
+ is
+ Ignored_HPD : Boolean;
+ begin
+ pragma Warnings (GNATprove, Off, "unused assignment to ""Ignored_HPD""",
+ Reason => "We want to clear pending events only");
+ Port_Detect.Hotplug_Detect (Port, Ignored_HPD);
+ pragma Warnings (GNATprove, On, "unused assignment to ""Ignored_HPD""");
+ end Clear_Hotplug_Detect;
+
+end HW.GFX.GMA.Port_Detect;