kern/48708: i915drmkms(4): Can't probe dual-link LVDS setting.

[nonakap%gmail.com@localhost]

>Number:         48708
>Category:       kern
>Synopsis:       i915drmkms(4): Can't probe dual-link LVDS setting.
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Apr 04 14:10:00 +0000 2014
>Originator:     NONAKA Kimihiro
>Release:        6.99.39
>Organization:
>Environment:
NetBSD koharu.myhome.local 6.99.39 NetBSD 6.99.39 (KOHARU) #2230: Fri Apr  4 
21:13:54 JST 2014  
nonaka@koharu.myhome.local:/usr/obj.amd64/sys/arch/amd64/compile/KOHARU amd64
>Description:
My ThinkPad E430 boot with DRMKMS kernel did not display correctly.
My notebook have 1600x900 LCD with dual-link LVDS. I think i915drmkms(4) can't 
probe dual-link LVDS setting.
>How-To-Repeat:
Boot with DRMKMS kernel on dual-link LVDS machine.
>Fix:
Apply following patch. code from OpenBSD.

Index: sys/external/bsd/drm2/dist/drm/i915/intel_bios.c
===================================================================
RCS file: /cvsroot/src/sys/external/bsd/drm2/dist/drm/i915/intel_bios.c,v
retrieving revision 1.2
diff -u -r1.2 intel_bios.c
--- sys/external/bsd/drm2/dist/drm/i915/intel_bios.c    18 Mar 2014 18:20:42 
-0000      1.2
+++ sys/external/bsd/drm2/dist/drm/i915/intel_bios.c    4 Apr 2014 12:11:20 
-0000
@@ -30,6 +30,13 @@
 #include <drm/i915_drm.h>
 #include "i915_drv.h"
 #include "intel_bios.h"
+#if defined(__i386__) || defined(__x86_64__)
+#include <dev/isa/isareg.h>
+#include <dev/isa/isavar.h>
+
+#define VGA_BIOS_ADDR  0xc0000
+#define VGA_BIOS_SIZE  0x10000
+#endif
 
 #define        SLAVE_ADDR1     0x70
 #define        SLAVE_ADDR2     0x72
@@ -719,6 +726,32 @@
        }
 #endif
 
+#if defined(__i386__) || defined(__x86_64__)
+       if (bdb == NULL) {
+               struct vbt_header *vbt = NULL;
+               size_t size;
+               int i;
+
+               bios = (u8 *)ISA_HOLE_VADDR(VGA_BIOS_ADDR);
+               size = VGA_BIOS_SIZE;
+
+               /* Scour memory looking for the VBT signature */
+               for (i = 0; i + 4 < size; i++) {
+                       if (!memcmp(bios + i, "$VBT", 4)) {
+                               vbt = (struct vbt_header *)(bios + i);
+                               break;
+                       }
+               }
+
+               if (vbt != NULL) {
+                       DRM_DEBUG_KMS("Using VBT from VGA BIOS: %20s\n",
+                                        vbt->signature);
+                       bdb = (struct bdb_header *)(bios + i + vbt->bdb_offset);
+               }
+               bios = NULL;
+       }
+#endif
+
        if (bdb == NULL) {
                struct vbt_header *vbt = NULL;
                size_t size;