[AGPGART] Improved AGPx8 handling.

If something fails, we should now explain what happened,
before we fall back to AGPx4 gracefully.
Signed-off-by: Dave Jones <davej@redhat.com>

drivers/char/agp/generic.c

@@ -458,29 +458,39 @@ static void agp_v3_parse_one(u32 *mode, u32 *cmd, u32 *tmp)
 		*mode |= AGPSTAT3_4X;
 	}
 
-	if (!((*cmd & AGPSTAT3_8X) && (*tmp & AGPSTAT3_8X) && (*mode & AGPSTAT3_8X)))
-		*cmd &= ~AGPSTAT3_8X;
-	else {
+	if (*mode & AGPSTAT3_8X) {
+		if (!(*cmd & AGPSTAT3_8X)) {
+			*cmd &= ~(AGPSTAT3_8X | AGPSTAT3_RSVD);
+			*cmd |= ~AGPSTAT3_4X;
+			printk ("%s requested AGPx8 but bridge not capable.\n", current->comm);
+			return;
+		}
+		if (!(*tmp & AGPSTAT3_8X)) {
+			*cmd &= ~(AGPSTAT3_8X | AGPSTAT3_RSVD);
+			*cmd |= ~AGPSTAT3_4X;
+			printk ("%s requested AGPx8 but device not capable.\n", current->comm);
+			return;
+		}
+		/* All set, bridge & device can do AGP x8*/
+		*cmd &= ~(AGPSTAT3_4X | AGPSTAT3_RSVD);
+		return;
+
+	} else {
+
 		/*
 		 * If we didn't specify AGPx8, we can only do x4.
 		 * If the hardware can't do x4, we're up shit creek, and never
 		 *  should have got this far.
 		 */
+		*cmd &= ~(AGPSTAT3_8X | AGPSTAT3_RSVD);
 		if ((*cmd & AGPSTAT3_4X) && (*tmp & AGPSTAT3_4X))
 			*cmd |= ~AGPSTAT3_4X;
 		else {
 			printk (KERN_INFO PFX "Badness. Don't know which AGP mode to set. "
 							"[cmd:%x tmp:%x fell back to:- cmd:%x tmp:%x]\n",
 							origcmd, origtmp, *cmd, *tmp);
-			return;
 		}
 	}
-
-	/* Clear out unwanted bits. */
-	if (*cmd & AGPSTAT3_8X)
-		*cmd &= ~(AGPSTAT3_4X | AGPSTAT3_RSVD);
-	if (*cmd & AGPSTAT3_4X)
-		*cmd &= ~(AGPSTAT3_8X | AGPSTAT3_RSVD);
 }
 
 //FIXME: This doesn't smell right.