drm/nouveau: Reset AGP before running the init scripts.

BIOS scripts usually make an attempt to reset the AGP controller,
however on some nv4x cards doing it properly involves switching FW off
and on: if we do that without updating the AGP bridge settings
accordingly (e.g. with the corresponding calls to agp_enable()) we
will be locking ourselves out of the card MMIO space. Do it from
nouveau_mem_reset_agp() before the init scripts are executed.
Signed-off-by: Francisco Jerez <currojerez@riseup.net>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_drv.c

@@ -259,6 +259,10 @@ nouveau_pci_resume(struct pci_dev *pdev)
 		return -1;
 	pci_set_master(dev->pdev);
 
+	/* Make sure the AGP controller is in a consistent state */
+	if (dev_priv->gart_info.type == NOUVEAU_GART_AGP)
+		nouveau_mem_reset_agp(dev);
+
 	NV_INFO(dev, "POSTing device...\n");
 	ret = nouveau_run_vbios_init(dev);
 	if (ret)

drivers/gpu/drm/nouveau/nouveau_drv.h

@@ -688,6 +688,7 @@ extern int  nouveau_card_init(struct drm_device *);
 extern int  nouveau_mem_detect(struct drm_device *dev);
 extern int  nouveau_mem_init(struct drm_device *);
 extern int  nouveau_mem_init_agp(struct drm_device *);
+extern int  nouveau_mem_reset_agp(struct drm_device *);
 extern void nouveau_mem_close(struct drm_device *);
 extern struct nouveau_tile_reg *nv10_mem_set_tiling(struct drm_device *dev,
 						    uint32_t addr,

drivers/gpu/drm/nouveau/nouveau_mem.c

@@ -341,18 +341,36 @@ nouveau_mem_detect(struct drm_device *dev)
 	return -ENOMEM;
 }
 
-#if __OS_HAS_AGP
-static void nouveau_mem_reset_agp(struct drm_device *dev)
+int
+nouveau_mem_reset_agp(struct drm_device *dev)
 {
-	uint32_t saved_pci_nv_1, saved_pci_nv_19, pmc_enable;
+#if __OS_HAS_AGP
+	uint32_t saved_pci_nv_1, pmc_enable;
+	int ret;
+
+	/* First of all, disable fast writes, otherwise if it's
+	 * already enabled in the AGP bridge and we disable the card's
+	 * AGP controller we might be locking ourselves out of it. */
+	if (dev->agp->acquired) {
+		struct drm_agp_info info;
+		struct drm_agp_mode mode;
+
+		ret = drm_agp_info(dev, &info);
+		if (ret)
+			return ret;
+
+		mode.mode = info.mode & ~0x10;
+		ret = drm_agp_enable(dev, mode);
+		if (ret)
+			return ret;
+	}
 
 	saved_pci_nv_1 = nv_rd32(dev, NV04_PBUS_PCI_NV_1);
-	saved_pci_nv_19 = nv_rd32(dev, NV04_PBUS_PCI_NV_19);
 
 	/* clear busmaster bit */
 	nv_wr32(dev, NV04_PBUS_PCI_NV_1, saved_pci_nv_1 & ~0x4);
-	/* clear SBA and AGP bits */
-	nv_wr32(dev, NV04_PBUS_PCI_NV_19, saved_pci_nv_19 & 0xfffff0ff);
+	/* disable AGP */
+	nv_wr32(dev, NV04_PBUS_PCI_NV_19, 0);
 
 	/* power cycle pgraph, if enabled */
 	pmc_enable = nv_rd32(dev, NV03_PMC_ENABLE);
@@ -364,11 +382,12 @@ static void nouveau_mem_reset_agp(struct drm_device *dev)
 	}
 
 	/* and restore (gives effect of resetting AGP) */
-	nv_wr32(dev, NV04_PBUS_PCI_NV_19, saved_pci_nv_19);
 	nv_wr32(dev, NV04_PBUS_PCI_NV_1, saved_pci_nv_1);
-}
 #endif
 
+	return 0;
+}
+
 int
 nouveau_mem_init_agp(struct drm_device *dev)
 {
@@ -378,11 +397,6 @@ nouveau_mem_init_agp(struct drm_device *dev)
 	struct drm_agp_mode mode;
 	int ret;
 
-	if (nouveau_noagp)
-		return 0;
-
-	nouveau_mem_reset_agp(dev);
-
 	if (!dev->agp->acquired) {
 		ret = drm_agp_acquire(dev);
 		if (ret) {
@@ -479,7 +493,8 @@ nouveau_mem_init(struct drm_device *dev)
 
 	/* GART */
 #if !defined(__powerpc__) && !defined(__ia64__)
-	if (drm_device_is_agp(dev) && dev->agp) {
+	if (drm_device_is_agp(dev) && dev->agp && !nouveau_noagp) {
+		nouveau_mem_reset_agp(dev);
 		ret = nouveau_mem_init_agp(dev);
 		if (ret)
 			NV_ERROR(dev, "Error initialising AGP: %d\n", ret);