drm/nouveau: assume no nv04 board has a DCB table

There's a report of a TNT2 where the DCB table pointer is *not* NULL
(it contains a part of a VBIOS data string), and we assume this means
a DCB table is present, causing all kinds of hilarity.

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

1 files changed, 12 insertions, 8 deletions

diff --git a/drivers/gpu/drm/nouveau/nouveau_bios.c b/drivers/gpu/drm/nouveau/nouveau_bios.c
index 9710e69898f6..9dd2efa07f68 100644
--- a/drivers/gpu/drm/nouveau/nouveau_bios.c
+++ b/drivers/gpu/drm/nouveau/nouveau_bios.c
@@ -5523,11 +5523,13 @@ void merge_like_dcb_entries(struct drm_device *dev, struct parsed_dcb *dcb)
         dcb->entries = newentries;
 }
 
-static int parse_dcb_table(struct drm_device *dev, struct nvbios *bios, bool twoHeads)
+static int
+parse_dcb_table(struct drm_device *dev, struct nvbios *bios, bool twoHeads)
 {
+        struct drm_nouveau_private *dev_priv = dev->dev_private;
         struct bios_parsed_dcb *bdcb = &bios->bdcb;
         struct parsed_dcb *dcb;
-        uint16_t dcbptr, i2ctabptr = 0;
+        uint16_t dcbptr = 0, i2ctabptr = 0;
         uint8_t *dcbtable;
         uint8_t headerlen = 0x4, entries = DCB_MAX_NUM_ENTRIES;
         bool configblock = true;
@@ -5538,16 +5540,18 @@ static int parse_dcb_table(struct drm_device *dev, struct nvbios *bios, bool two
         dcb->entries = 0;
 
         /* get the offset from 0x36 */
-        dcbptr = ROM16(bios->data[0x36]);
+        if (dev_priv->card_type > NV_04) {
+                dcbptr = ROM16(bios->data[0x36]);
+                if (dcbptr == 0x0000)
+                        NV_WARN(dev, "No output data (DCB) found in BIOS\n");
+        }
 
+        /* this situation likely means a really old card, pre DCB */
         if (dcbptr == 0x0) {
-                NV_WARN(dev, "No output data (DCB) found in BIOS, "
-                               "assuming a CRT output exists\n");
-                /* this situation likely means a really old card, pre DCB */
+                NV_INFO(dev, "Assuming a CRT output exists\n");
                 fabricate_vga_output(dcb, LEGACY_I2C_CRT, 1);
 
-                if (nv04_tv_identify(dev,
-                                     bios->legacy.i2c_indices.tv) >= 0)
+                if (nv04_tv_identify(dev, bios->legacy.i2c_indices.tv) >= 0)
                         fabricate_tv_output(dcb, twoHeads);
 
                 return 0;