[AGPGART] Merge missing chunk of NVIDIA nForce agpgart driver.

This bit has been in the 2.4 driver since it appeared, but I dropped
it (partly deliberatly), and then forgot all about it.
Turns out that some systems really need this stuff, as their BIOS hasn't
set up the IORRs.

http://bugme.osdl.org/show_bug.cgi?id=1521

drivers/char/agp/nvidia-agp.c

@@ -46,10 +46,54 @@ static int nvidia_fetch_size(void)
 	return 0;
 }
 
+#define SYSCFG          0xC0010010
+#define IORR_BASE0      0xC0010016
+#define IORR_MASK0      0xC0010017
+#define AMD_K7_NUM_IORR 2
+
+static int nvidia_init_iorr(u32 base, u32 size)
+{
+	u32 base_hi, base_lo;
+	u32 mask_hi, mask_lo;
+	u32 sys_hi, sys_lo;
+	u32 iorr_addr, free_iorr_addr;
+
+	/* Find the iorr that is already used for the base */
+	/* If not found, determine the uppermost available iorr */
+	free_iorr_addr = AMD_K7_NUM_IORR;
+	for(iorr_addr = 0; iorr_addr < AMD_K7_NUM_IORR; iorr_addr++) {
+		rdmsr(IORR_BASE0 + 2 * iorr_addr, base_lo, base_hi);
+		rdmsr(IORR_MASK0 + 2 * iorr_addr, mask_lo, mask_hi);
+
+		if ((base_lo & 0xfffff000) == (base & 0xfffff000))
+			break;
+
+		if ((mask_lo & 0x00000800) == 0)
+			free_iorr_addr = iorr_addr;
+	}
+	
+	if (iorr_addr >= AMD_K7_NUM_IORR) {
+		iorr_addr = free_iorr_addr;
+		if (iorr_addr >= AMD_K7_NUM_IORR)
+			return -EINVAL;
+	}
+    base_hi = 0x0;
+    base_lo = (base & ~0xfff) | 0x18;
+    mask_hi = 0xf;
+    mask_lo = ((~(size - 1)) & 0xfffff000) | 0x800;
+    wrmsr(IORR_BASE0 + 2 * iorr_addr, base_lo, base_hi);
+    wrmsr(IORR_MASK0 + 2 * iorr_addr, mask_lo, mask_hi);
+
+    rdmsr(SYSCFG, sys_lo, sys_hi);
+    sys_lo |= 0x00100000;
+    wrmsr(SYSCFG, sys_lo, sys_hi);
+
+	return 0;
+}
 
 static int nvidia_configure(void)
 {
-	int i, num_dirs;
+	int i, rc, num_dirs;
 	u32 apbase, aplimit;
 	struct aper_size_info_8 *current_size;
 	u32 temp;
@@ -69,6 +113,8 @@ static int nvidia_configure(void)
 	pci_write_config_dword(nvidia_private.dev_2, NVIDIA_2_APLIMIT, aplimit);
 	pci_write_config_dword(nvidia_private.dev_3, NVIDIA_3_APBASE, apbase);
 	pci_write_config_dword(nvidia_private.dev_3, NVIDIA_3_APLIMIT, aplimit);
+	if (0 != (rc = nvidia_init_iorr(apbase, current_size->size * 1024 * 1024)))
+		return rc;
 
 	/* directory size is 64k */
 	num_dirs = current_size->size / 64;
@@ -122,6 +168,10 @@ static void nvidia_cleanup(void)
 	previous_size = A_SIZE_8(agp_bridge->previous_size);
 	pci_write_config_byte(agp_bridge->dev, NVIDIA_0_APSIZE,
 		previous_size->size_value);
+
+	/* restore iorr for previous aperture size */
+	nvidia_init_iorr(agp_bridge->gart_bus_addr,
+		previous_size->size * 1024 * 1024);
 }