[SeaBIOS] [PATCH v4] Add basic MXM 3.0 interrupt support

[Riku Viitanen]

VGAROMs on MXM graphics cards need certain int15h functions present
to function properly.

On HP EliteBook 8560w with coreboot and Quadro 2000M, this warning
is displayed for 30 seconds, making every boot extremely slow:

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

This patch implements the minimum functionality to get rid of it: the
functions 0 and 1, version 3.0 of the specification [1]. Older version
2.1 is not implemented.

Functions are enabled only if romfile "mxm-30-sis" exists. These functions
are specific to the MXM revision, but not the board or GPU. Some boards
might require more of the optional functions to be implemented, however.

- Function 0 returns information about supported functions and revision.

- Function 1 returns a pointer to a MXM configuration structure in low
memory. This is copied from romfile "mxm-30-sis". It can be extracted
from vendor BIOS, by using this same interrupt. I wrote a tool [2] to do
that from Linux.

TEST: HP EliteBook 8560w boots without error and delay, graphics work.

[1]: MXM Graphics Module Software Specification Version 3.0, Revision 1.1
[2]: https://codeberg.org/Riku_V/mxmdump/

Signed-off-by: Riku Viitanen [e-mail]
---
 src/vgahooks.c | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 79 insertions(+)

diff --git a/src/vgahooks.c b/src/vgahooks.c
index 1f149532..6adf5b9b 100644
--- a/src/vgahooks.c
+++ b/src/vgahooks.c
@@ -11,13 +11,16 @@
 #include "hw/pcidevice.h" // pci_find_device
 #include "hw/pci_ids.h" // PCI_VENDOR_ID_VIA
 #include "hw/pci_regs.h" // PCI_VENDOR_ID
+#include "malloc.h" // malloc_low
 #include "output.h" // dprintf
+#include "romfile.h" // struct romfile_s, romfile_find
 #include "string.h" // strcmp
 #include "util.h" // handle_155f, handle_157f

#define VH_VIA 1
 #define VH_INTEL 2
 #define VH_SMI 3
+#define VH_MXM30 4

int VGAHookHandlerType VARFSEG;

@@ -296,6 +299,77 @@ winent_mb6047_setup(struct pci_device *pci)
     SmiBootDisplay = 0x02;
 }

+/****************************************************************
+ * MXM 3.0 hooks
+ ****************************************************************/
+
+void *MXM30SIS VARFSEG;
+
+/* Function 0: Return Specification Support Level */
+static void
+mxm30_F00(struct bregs *regs)
+{
+    regs->ax = 0x005f; /* Success */
+    regs->bl = 0x30; /* MXM version 3.0 */
+    regs->cx = (1<<0) | (1<<1); /* Supported functions */
+    set_success(regs);
+}
+
+/* Function 1: Return Pointer to MXM System Information Structure */
+static void
+mxm30_F01(struct bregs *regs)
+{
+    switch (regs->cx) {
+    case 0x0030:
+        regs->ax = 0x005f; /* Success */
+        regs->es = (u32)GET_GLOBAL(MXM30SIS)/16;
+        regs->di = (u32)GET_GLOBAL(MXM30SIS)%16;
+        set_success(regs);
+        break;
+    default:
+        handle_155fXX(regs);
+        break;
+    }
+}
+
+static void
+mxm30_155f80(struct bregs *regs)
+{
+    switch (regs->bx) {
+    case 0xff00: mxm30_F00(regs); break;
+    case 0xff01: mxm30_F01(regs); break;
+    default:     handle_155fXX(regs); break;
+    }
+}
+
+static void
+mxm30_155f(struct bregs *regs)
+{
+    switch (regs->al) {
+    case 0x80: mxm30_155f80(regs); break;
+    default:   handle_155fXX(regs); break;
+    }
+}
+
+static void
+mxm30_setup(struct romfile_s *sis_file)
+{
+    /* Load MXM System Information Structure into low memory */
+    MXM30SIS = malloc_low(sis_file->size);
+    if (!MXM30SIS) {
+        warn_noalloc();
+        return;
+    }
+    int ret = sis_file->copy(sis_file, MXM30SIS, sis_file->size);
+    if (ret < 0) {
+        free(MXM30SIS);
+        MXM30SIS = NULL;
+        return;
+    }
+
+    VGAHookHandlerType = VH_MXM30;
+}
+
 /****************************************************************
  * Entry and setup
  ****************************************************************/
@@ -313,6 +387,7 @@ handle_155f(struct bregs *regs)
     switch (htype) {
     case VH_VIA:   via_155f(regs); break;
     case VH_INTEL: intel_155f(regs); break;
+    case VH_MXM30: mxm30_155f(regs); break;
     default:       handle_155fXX(regs); break;
     }
 }
@@ -340,6 +415,8 @@ vgahook_setup(struct pci_device *pci)
     if (!CONFIG_VGAHOOKS)
         return;

+    struct romfile_s *mxm30sis = romfile_find("mxm-30-sis");
+
     if (strcmp(CBvendor, "KONTRON") == 0 && strcmp(CBpart, "986LCD-M") == 0)
         kontron_setup(pci);
     else if (strcmp(CBvendor, "GETAC") == 0 && strcmp(CBpart, "P470") == 0)
@@ -352,4 +429,6 @@ vgahook_setup(struct pci_device *pci)
         via_setup(pci);
     else if (pci->vendor == PCI_VENDOR_ID_INTEL)
         intel_setup(pci);
+    else if (mxm30sis != NULL)
+        mxm30_setup(mxm30sis);
 }