From 270ac30b862c58c69455dbdace716044d29b20e2 Mon Sep 17 00:00:00 2001
From: Riku Viitanen <riku.viitanen@protonmail.com>
Date: Sat, 10 Feb 2024 21:38:17 +0200
Subject: [PATCH 2/4] vgahooks, optionroms: implement mxm 3.0 interrupts

VGAROMs on MXM graphics cards need certain int15h functions present.

Tested on a HP EliteBook 8560w with coreboot and Quadro 2000M. A warning
is displayed for 30 seconds and performance is nerfed:

	ERROR: Valid MXM Structure not found.
	POST halted for 30 seconds, P-state limited to P10...

This patch implements the minimum required on this system (and implemented
by the OEM BIOS): functions 0 and 1.

These functions are specific to the MXM 3.0 Software Specification,
earlier versions are not implemented due to lack of hardware. Documentation
for versions 2.1 and 3.0 can be found freely online.

Functions aren't specific to mainboards or GPUs (though some mainboards
could need more functions implemented). The structure is
mainboard-specific and is read from romfile "mxm-30-sis".

It can be extracted from vendor BIOS by running those same interrupts.
I wrote a tool to do it on Linux: https://codeberg.org/Riku_V/mxmdump/

Signed-off-by: Riku Viitanen <riku.viitanen@protonmail.com>
---
 src/optionroms.c |  9 +++++++
 src/vgahooks.c   | 69 ++++++++++++++++++++++++++++++++++++++++++++++++
 src/vgahooks.h   |  9 +++++++
 3 files changed, 87 insertions(+)
 create mode 100644 src/vgahooks.h

diff --git a/src/optionroms.c b/src/optionroms.c
index e906ab97..fcce7900 100644
--- a/src/optionroms.c
+++ b/src/optionroms.c
@@ -22,6 +22,7 @@
 #include "string.h" // memset
 #include "util.h" // get_pnp_offset
 #include "tcgbios.h" // tpm_*
+#include "vgahooks.h" // MXM30SIS
 
 static int EnforceChecksum, S3ResumeVga, RunPCIroms;
 
@@ -463,6 +464,14 @@ vgarom_setup(void)
     RunPCIroms = romfile_loadint("etc/pci-optionrom-exec", 2);
     ScreenAndDebug = romfile_loadint("etc/screen-and-debug", 1);
 
+    // Load MXM 3.0 System Information Structure
+    void *mxm_sis = romfile_loadfile_g("mxm-30-sis", NULL, &malloc_low, 0);
+    if (mxm_sis) {
+        MXM30SIS = (u32)mxm_sis;
+    } else {
+        MXM30SIS = 0;
+    }
+
     // Clear option rom memory
     memset((void*)BUILD_ROM_START, 0, rom_get_max() - BUILD_ROM_START);
 
diff --git a/src/vgahooks.c b/src/vgahooks.c
index 1f149532..a94840b2 100644
--- a/src/vgahooks.c
+++ b/src/vgahooks.c
@@ -18,8 +18,10 @@
 #define VH_VIA 1
 #define VH_INTEL 2
 #define VH_SMI 3
+#define VH_MXM 4
 
 int VGAHookHandlerType VARFSEG;
+u32 MXM30SIS VARFSEG;
 
 static void
 handle_155fXX(struct bregs *regs)
@@ -59,6 +61,7 @@ via_155f02(struct bregs *regs)
     dprintf(1, "Warning: VGA TV/CRT output type is hardcoded\n");
 }
 
+
 static void
 via_155f18(struct bregs *regs)
 {
@@ -296,6 +299,69 @@ winent_mb6047_setup(struct pci_device *pci)
     SmiBootDisplay = 0x02;
 }
 
+/****************************************************************
+ * MXM VGA hooks
+ ****************************************************************/
+
+// Function 0: Return Specification Support Level
+static void
+mxm_V30_F00(struct bregs *regs)
+{
+    regs->ax = 0x005f; // Success
+    regs->bl = 0x30; // MXM 3.0
+    regs->cx = 0x0003; // Supported Functions
+    set_success(regs);
+}
+
+// Function 1: Return a Pointer to the MXM Structure
+static void
+mxm_V30_F01(struct bregs *regs)
+{
+    switch (regs->cx) {
+    case 0x0030:
+        regs->ax = 0x005f; // Success
+        regs->es = GET_GLOBAL(MXM30SIS)/16;
+        regs->di = GET_GLOBAL(MXM30SIS)%16;
+        set_success(regs);
+        break;
+    default:
+        handle_155fXX(regs);
+        break;
+    }
+}
+
+static void
+mxm_V30(struct bregs *regs)
+{
+    switch (regs->bx) {
+    case 0xff00: mxm_V30_F00(regs); break;
+    case 0xff01: mxm_V30_F01(regs); break;
+    default:   handle_155fXX(regs); break;
+    }
+}
+
+static void
+mxm_155f80(struct bregs *regs)
+{
+    // TODO: implement other versions, like 2.1
+    mxm_V30(regs);
+}
+
+static void
+mxm_155f(struct bregs *regs)
+{
+    switch (regs->al) {
+    case 0x80: mxm_155f80(regs); break;
+    default:   handle_155fXX(regs); break;
+    }
+}
+
+void
+mxm_setup(void)
+{
+    VGAHookHandlerType = VH_MXM;
+}
+
 /****************************************************************
  * Entry and setup
  ****************************************************************/
@@ -313,6 +379,7 @@ handle_155f(struct bregs *regs)
     switch (htype) {
     case VH_VIA:   via_155f(regs); break;
     case VH_INTEL: intel_155f(regs); break;
+    case VH_MXM:   mxm_155f(regs); break;
     default:       handle_155fXX(regs); break;
     }
 }
@@ -352,4 +419,6 @@ vgahook_setup(struct pci_device *pci)
         via_setup(pci);
     else if (pci->vendor == PCI_VENDOR_ID_INTEL)
         intel_setup(pci);
+    else if (GET_GLOBAL(MXM30SIS))
+        mxm_setup();
 }
diff --git a/src/vgahooks.h b/src/vgahooks.h
new file mode 100644
index 00000000..f0c203af
--- /dev/null
+++ b/src/vgahooks.h
@@ -0,0 +1,9 @@
+#ifndef __VGAHOOKS_H
+#define __VGAHOOKS_H
+
+#include "types.h" // u32
+
+extern u32 MXM30SIS;
+
+
+#endif // vgahooks.h
-- 
2.39.5

