[PATCH v4 3/5] drm/nouveau: Fix drm_driver struct/nouveau.atomic parameter handling

[Lyude Paul <lyude@redhat.com>]

The way we handled the nouveau.atomic module parameter before was fairly
broken, and had a number of issues:

- It was only ever actually parsed in the case of PCI devices.
- When nouveau.atomic was enabled, it would add the cap for atomic
  modesetting to the global driver_pci structure. This meant that if one
  GPU on a system supported atomic and another didn't, it would still get
  enabled for both.

Looking into this exposed further silliness in the way that we actually
handle the drm_driver struct. We have one global structure for platform
devices, and another for PCI devices - both of which are literally
identical.

So before we start preparing to enable atomic modesetting by default, let's
fix this. Instead of sharing driver_pci and driver_platform, we move the
drm_driver struct we use over to the nouveau_drm struct, and then copy the
contents of driver_stub over to it. We then convert driver_stub to a const,
and move the handling of the nouveau.atomic module parameter into
nouveau_drm_device_new(), and conditionally add the atomic modesetting
capability to the embedded drm_driver struct.

Doing this is also preferable, as the next step for enabling atomic
modesetting by default will be ensuring that we don't enable it for legacy
devices that still don't support it. This requires only checking the atomic
modesetting module parameter after the NVIF device is ready, as this allows
us to check the GPU family that nouveau is running on.

Signed-off-by: Lyude Paul <lyude@redhat.com>

---
V2:
* s/driver_pci/drm_driver/
* Dynamically allocate drm_driver struct, get rid of duplicate global
  driver structs to fix another Sashiko issue.
V3:
* Don't use devm (sashiko)
V4:
* Don't return 0 by mistake (thanks C)
* Go back to the old style of error handling since we're not using a second
  allocation for drm_driver anymore.

 drivers/gpu/drm/nouveau/nouveau_drm.c | 56 ++++++++++++---------------
 drivers/gpu/drm/nouveau/nouveau_drv.h |  1 +
 2 files changed, 25 insertions(+), 32 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c
index 6940e774ace07..9cd12ebc7e449 100644
--- a/drivers/gpu/drm/nouveau/nouveau_drm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_drm.c
@@ -111,9 +111,7 @@ MODULE_PARM_DESC(runpm, "disable (0), force enable (1), optimus only default (-1
 static int nouveau_runtime_pm = -1;
 module_param_named(runpm, nouveau_runtime_pm, int, 0400);
 
-static struct drm_driver driver_stub;
-static struct drm_driver driver_pci;
-static struct drm_driver driver_platform;
+static const struct drm_driver driver_stub;
 
 #ifdef CONFIG_DEBUG_FS
 struct dentry *nouveau_debugfs_root;
@@ -727,8 +725,7 @@ nouveau_drm_device_del(struct nouveau_drm *drm)
 }
 
 static struct nouveau_drm *
-nouveau_drm_device_new(const struct drm_driver *drm_driver, struct device *parent,
-		       struct nvkm_device *device)
+nouveau_drm_device_new(struct device *parent, struct nvkm_device *device)
 {
 	static const struct nvif_mclass
 	mmus[] = {
@@ -744,12 +741,14 @@ nouveau_drm_device_new(const struct drm_driver *drm_driver, struct device *paren
 	if (!drm)
 		return ERR_PTR(-ENOMEM);
 
+	drm->drm_driver = driver_stub;
 	drm->nvkm = device;
 
-	drm->dev = drm_dev_alloc(drm_driver, parent);
+	drm->dev = drm_dev_alloc(&drm->drm_driver, parent);
 	if (IS_ERR(drm->dev)) {
 		ret = PTR_ERR(drm->dev);
-		goto err_free_drm;
+		kfree(drm);
+		return ERR_PTR(ret);
 	}
 
 	drm->dev->dev_private = drm;
@@ -762,43 +761,42 @@ nouveau_drm_device_new(const struct drm_driver *drm_driver, struct device *paren
 	ret = nvif_driver_init(NULL, nouveau_config, nouveau_debug, "drm",
 			       nouveau_name(drm->dev), &drm->_client);
 	if (ret)
-		goto err_device_del;
+		goto done;
 
 	ret = nvif_device_ctor(&drm->_client, "drmDevice", &drm->device);
 	if (ret) {
 		NV_ERROR(drm, "Device allocation failed: %d\n", ret);
-		goto err_device_del;
+		goto done;
 	}
 
+	if (nouveau_atomic)
+		drm->drm_driver.driver_features |= DRIVER_ATOMIC;
+
 	ret = nvif_device_map(&drm->device);
 	if (ret) {
 		NV_ERROR(drm, "Failed to map PRI: %d\n", ret);
-		goto err_device_del;
+		goto done;
 	}
 
 	ret = nvif_mclass(&drm->device.object, mmus);
 	if (ret < 0) {
 		NV_ERROR(drm, "No supported MMU class\n");
-		goto err_device_del;
+		goto done;
 	}
 
 	ret = nvif_mmu_ctor(&drm->device.object, "drmMmu", mmus[ret].oclass, &drm->mmu);
 	if (ret) {
 		NV_ERROR(drm, "MMU allocation failed: %d\n", ret);
-		goto err_device_del;
+		goto done;
 	}
 
-	return 0;
-
-err_free_drm:
-	kfree(drm);
-
-	return ERR_PTR(ret);
-
-err_device_del:
-	nouveau_drm_device_del(drm);
+done:
+	if (ret) {
+		nouveau_drm_device_del(drm);
+		drm = NULL;
+	}
 
-	return ERR_PTR(ret);
+	return ret ? ERR_PTR(ret) : drm;
 }
 
 /*
@@ -877,16 +875,13 @@ static int nouveau_drm_probe(struct pci_dev *pdev,
 		return ret;
 
 	/* Remove conflicting drivers (vesafb, efifb etc). */
-	ret = aperture_remove_conflicting_pci_devices(pdev, driver_pci.name);
+	ret = aperture_remove_conflicting_pci_devices(pdev, driver_stub.name);
 	if (ret)
 		goto fail_nvkm;
 
 	pci_set_master(pdev);
 
-	if (nouveau_atomic)
-		driver_pci.driver_features |= DRIVER_ATOMIC;
-
-	drm = nouveau_drm_device_new(&driver_pci, &pdev->dev, device);
+	drm = nouveau_drm_device_new(&pdev->dev, device);
 	if (IS_ERR(drm)) {
 		ret = PTR_ERR(drm);
 		goto fail_nvkm;
@@ -1363,7 +1358,7 @@ nouveau_driver_fops = {
 	.fop_flags = FOP_UNSIGNED_OFFSET,
 };
 
-static struct drm_driver
+static const struct drm_driver
 driver_stub = {
 	.driver_features = DRIVER_GEM |
 			   DRIVER_SYNCOBJ | DRIVER_SYNCOBJ_TIMELINE |
@@ -1460,7 +1455,7 @@ nouveau_platform_device_create(const struct nvkm_device_tegra_func *func,
 	if (err)
 		goto err_free;
 
-	drm = nouveau_drm_device_new(&driver_platform, &pdev->dev, *pdevice);
+	drm = nouveau_drm_device_new(&pdev->dev, *pdevice);
 	if (IS_ERR(drm)) {
 		err = PTR_ERR(drm);
 		goto err_free;
@@ -1485,9 +1480,6 @@ nouveau_drm_init(void)
 {
 	int ret;
 
-	driver_pci = driver_stub;
-	driver_platform = driver_stub;
-
 	nouveau_display_options();
 
 	if (nouveau_modeset == -1) {
diff --git a/drivers/gpu/drm/nouveau/nouveau_drv.h b/drivers/gpu/drm/nouveau/nouveau_drv.h
index 5fc75dc750ed0..5cc0001134e74 100644
--- a/drivers/gpu/drm/nouveau/nouveau_drv.h
+++ b/drivers/gpu/drm/nouveau/nouveau_drv.h
@@ -216,6 +216,7 @@ struct nouveau_drm {
 
 	struct nouveau_cli client;
 	struct drm_device *dev;
+	struct drm_driver drm_driver;
 
 	struct list_head clients;
 
-- 
2.55.0