1 files changed, 33 insertions, 3 deletions

diff --git a/drivers/char/agp/generic.c b/drivers/char/agp/generic.c
index 5ff457b..3491d6f 100644
--- a/drivers/char/agp/generic.c
+++ b/drivers/char/agp/generic.c
@@ -419,6 +419,31 @@ static void agp_v2_parse_one(u32 *requested_mode, u32 *bridge_agpstat, u32 *vga_
 		*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) {
@@ -940,6 +965,9 @@ int agp_generic_insert_memory(struct agp_memory * mem, off_t pg_start, int type)
 	if (!bridge)
 		return -EINVAL;
 
+	if (mem->page_count == 0)
+		return 0;
+
 	temp = bridge->current_size;
 
 	switch (bridge->driver->size_type) {
@@ -991,8 +1019,8 @@ int agp_generic_insert_memory(struct agp_memory * mem, off_t pg_start, int type)
 
 	for (i = 0, j = pg_start; i < mem->page_count; i++, j++) {
 		writel(bridge->driver->mask_memory(bridge, mem->memory[i], mem->type), bridge->gatt_table+j);
-		readl(bridge->gatt_table+j);	/* PCI Posting. */
 	}
+	readl(bridge->gatt_table+j-1);	/* PCI Posting. */
 
 	bridge->driver->tlb_flush(mem);
 	return 0;
@@ -1009,6 +1037,9 @@ int agp_generic_remove_memory(struct agp_memory *mem, off_t pg_start, int type)
 	if (!bridge)
 		return -EINVAL;
 
+	if (mem->page_count == 0)
+		return 0;
+
 	if (type != 0 || mem->type != 0) {
 		/* The generic routines know nothing of memory types */
 		return -EINVAL;
@@ -1017,10 +1048,9 @@ int agp_generic_remove_memory(struct agp_memory *mem, off_t pg_start, int type)
 	/* AK: bogus, should encode addresses > 4GB */
 	for (i = pg_start; i < (mem->page_count + pg_start); i++) {
 		writel(bridge->scratch_page, bridge->gatt_table+i);
-		readl(bridge->gatt_table+i);	/* PCI Posting. */
 	}
+	readl(bridge->gatt_table+i-1);	/* PCI Posting. */
 
-	global_cache_flush();
 	bridge->driver->tlb_flush(mem);
 	return 0;
 }