drm/nouveau/bios: fetch the vbios from PROM using only aligned 32-bit accesses

Other kind of accesses are unreliable on Kepler cards. As advised by NVIDIA,
let's only use 32-bit accesses to fetch the vbios from PROM.

This fixes vbios fetching on my nve7 which failed in certain specific
conditions.

I suggest we Cc stable, for all kernels they still maintain after the big
rewrite.

Suggested-by: Christian Zander <czander@nvidia.com>
Signed-off-by: Martin Peres <martin.peres@free.fr>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

1 files changed, 19 insertions, 14 deletions

diff --git a/drivers/gpu/drm/nouveau/core/subdev/bios/base.c b/drivers/gpu/drm/nouveau/core/subdev/bios/base.c
index 56085304a847..e9df94f96d78 100644
--- a/drivers/gpu/drm/nouveau/core/subdev/bios/base.c
+++ b/drivers/gpu/drm/nouveau/core/subdev/bios/base.c
@@ -157,6 +157,10 @@ nouveau_bios_shadow_prom(struct nouveau_bios *bios)
                 pcireg = 0x001850;
         access = nv_mask(bios, pcireg, 0x00000001, 0x00000000);
 
+        /* WARNING: PROM accesses should always be 32-bits aligned. Other
+         * accesses work on most chipset but do not on Kepler chipsets
+         */
+
         /* bail if no rom signature, with a workaround for a PROM reading
          * issue on some chipsets.  the first read after a period of
          * inactivity returns the wrong result, so retry the first header
@@ -164,31 +168,32 @@ nouveau_bios_shadow_prom(struct nouveau_bios *bios)
          */
         i = 16;
         do {
-                if (nv_rd08(bios, 0x300000) == 0x55)
+                if ((nv_rd32(bios, 0x300000) & 0xffff) == 0xaa55)
                         break;
         } while (i--);
 
-        if (!i || nv_rd08(bios, 0x300001) != 0xaa)
-                goto out;
-
-        /* additional check (see note below) - read PCI record header */
-        pcir = nv_rd08(bios, 0x300018) |
-               nv_rd08(bios, 0x300019) << 8;
-        if (nv_rd08(bios, 0x300000 + pcir) != 'P' ||
-            nv_rd08(bios, 0x300001 + pcir) != 'C' ||
-            nv_rd08(bios, 0x300002 + pcir) != 'I' ||
-            nv_rd08(bios, 0x300003 + pcir) != 'R')
+        if (!i)
                 goto out;
 
         /* read entire bios image to system memory */
-        bios->size = nv_rd08(bios, 0x300002) * 512;
+        bios->size = ((nv_rd32(bios, 0x300000) >> 16) & 0xff) * 512;
         if (!bios->size)
                 goto out;
 
         bios->data = kmalloc(bios->size, GFP_KERNEL);
         if (bios->data) {
-                for (i = 0; i < bios->size; i++)
-                        nv_wo08(bios, i, nv_rd08(bios, 0x300000 + i));
+                for (i = 0; i < bios->size; i+=4)
+                        nv_wo32(bios, i, nv_rd32(bios, 0x300000 + i));
+        }
+
+        /* check the PCI record header */
+        pcir = nv_ro16(bios, 0x0018);
+        if (bios->data[pcir + 0] != 'P' ||
+            bios->data[pcir + 1] != 'C' ||
+            bios->data[pcir + 2] != 'I' ||
+            bios->data[pcir + 3] != 'R') {
+                bios->size = 0;
+                kfree(bios->data);
         }
 
 out: