Some dumb bridges are programmed to disobey the AGP2 spec.
This is likely a BIOS misprogramming rather than poweron default, or
it would be a lot more common.
AGPv2 spec 6.1.9 states:
"The RATE field indicates the data transfer rates supported by this
device. A.G.P. devices must report all that apply."
Fix them up as best we can.
This will prevent errors like..
agpgart: Found an AGP 3.5 compliant device at 0000:00:00.0.
agpgart: req mode
1f000201 bridge_agpstat
1f000a14 vga_agpstat
2f000217.
agpgart: Device is in legacy mode, falling back to 2.x
agpgart: Putting AGP V2 device at 0000:00:00.0 into 0x mode
agpgart: Putting AGP V2 device at 0000:01:00.0 into 0x mode
agpgart: Putting AGP V2 device at 0000:01:00.1 into 0x mode
https://bugs.freedesktop.org/show_bug.cgi?id=8816
Signed-off-by: Dave Jones <davej@redhat.com>
*requested_mode &= ~AGP2_RESERVED_MASK;
}
*requested_mode &= ~AGP2_RESERVED_MASK;
}
+ /*
+ * Some dumb bridges are programmed to disobey the AGP2 spec.
+ * This is likely a BIOS misprogramming rather than poweron default, or
+ * it would be a lot more common.
+ * https://bugs.freedesktop.org/show_bug.cgi?id=8816
+ * AGPv2 spec 6.1.9 states:
+ * The RATE field indicates the data transfer rates supported by this
+ * device. A.G.P. devices must report all that apply.
+ * Fix them up as best we can.
+ */
+ switch (*bridge_agpstat & 7) {
+ case 4:
+ *bridge_agpstat |= (AGPSTAT2_2X | AGPSTAT2_1X);
+ printk(KERN_INFO PFX "BIOS bug. AGP bridge claims to only support x4 rate"
+ "Fixing up support for x2 & x1\n");
+ break;
+ case 2:
+ *bridge_agpstat |= AGPSTAT2_1X;
+ printk(KERN_INFO PFX "BIOS bug. AGP bridge claims to only support x2 rate"
+ "Fixing up support for x1\n");
+ break;
+ default:
+ break;
+ }
+
/* Check the speed bits make sense. Only one should be set. */
tmp = *requested_mode & 7;
switch (tmp) {
/* Check the speed bits make sense. Only one should be set. */
tmp = *requested_mode & 7;
switch (tmp) {