[PATCH v6 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 instead
create driver_legacy_kms and driver_atomic_kms, each of which is identical
except for the DRIVER_ATOMIC capabilities flag, and then assign either
depending on the nouveau_atomic module parameter.

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 NVKM 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)
V6:
* Don't embed drm_driver into drm_device, just create two separate
  hardcoded structs
* Move the check earlier

 drivers/gpu/drm/nouveau/nouveau_drm.c | 100 +++++++++++++++-----------
 1 file changed, 58 insertions(+), 42 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c
index 451009adee0de..d021a3049be1a 100644
--- a/drivers/gpu/drm/nouveau/nouveau_drm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_drm.c
@@ -111,9 +111,8 @@ 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_legacy_kms;
+static const struct drm_driver driver_atomic_kms;
 
 #ifdef CONFIG_DEBUG_FS
 struct dentry *nouveau_debugfs_root;
@@ -727,8 +726,7 @@ 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[] = {
@@ -737,16 +735,21 @@ nouveau_drm_device_new(const struct drm_driver *drm_driver, struct device *paren
 		{ NVIF_CLASS_MMU_NV04 , -1 },
 		{}
 	};
+	const struct drm_driver *driver;
 	struct nouveau_drm *drm;
 	int ret;
 
+	if (nouveau_atomic)
+		driver = &driver_atomic_kms;
+	else
+		driver = &driver_legacy_kms;
+
 	drm = kzalloc_obj(*drm);
 	if (!drm)
 		return ERR_PTR(-ENOMEM);
 
 	drm->nvkm = device;
-
-	drm->dev = drm_dev_alloc(drm_driver, parent);
+	drm->dev = drm_dev_alloc(driver, parent);
 	if (IS_ERR(drm->dev)) {
 		ret = PTR_ERR(drm->dev);
 		kfree(drm);
@@ -874,16 +877,13 @@ 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_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;
@@ -1360,35 +1360,54 @@ nouveau_driver_fops = {
 	.fop_flags = FOP_UNSIGNED_OFFSET,
 };
 
-static struct drm_driver
-driver_stub = {
-	.driver_features = DRIVER_GEM |
-			   DRIVER_SYNCOBJ | DRIVER_SYNCOBJ_TIMELINE |
-			   DRIVER_MODESET |
-			   DRIVER_RENDER,
-	.open = nouveau_drm_open,
-	.postclose = nouveau_drm_postclose,
-
-#if defined(CONFIG_DEBUG_FS)
-	.debugfs_init = nouveau_drm_debugfs_init,
+#ifdef CONFIG_DEBUG_FS
+#define NOUVEAU_DEBUGFS_OPS .debugfs_init = nouveau_drm_debugfs_init,
+#else
+#define NOUVEAU_DEBUGFS_OPS
 #endif
 
-	.ioctls = nouveau_ioctls,
-	.num_ioctls = ARRAY_SIZE(nouveau_ioctls),
-	.fops = &nouveau_driver_fops,
-
-	.gem_prime_import_sg_table = nouveau_gem_prime_import_sg_table,
-
-	.dumb_create = nouveau_display_dumb_create,
-	.dumb_map_offset = drm_gem_ttm_dumb_map_offset,
-
-	DRM_FBDEV_TTM_DRIVER_OPS,
+#define NOUVEAU_DRIVER_OPS                                              \
+	.open = nouveau_drm_open,                                       \
+	.postclose = nouveau_drm_postclose,                             \
+                                                                        \
+	NOUVEAU_DEBUGFS_OPS						\
+                                                                        \
+	.ioctls = nouveau_ioctls,                                       \
+	.num_ioctls = ARRAY_SIZE(nouveau_ioctls),                       \
+	.fops = &nouveau_driver_fops,                                   \
+                                                                        \
+	.gem_prime_import_sg_table = nouveau_gem_prime_import_sg_table, \
+                                                                        \
+	.dumb_create = nouveau_display_dumb_create,                     \
+	.dumb_map_offset = drm_gem_ttm_dumb_map_offset,                 \
+                                                                        \
+	DRM_FBDEV_TTM_DRIVER_OPS,                                       \
+                                                                        \
+	.name = DRIVER_NAME,                                            \
+	.desc = DRIVER_DESC,                                            \
+	.major = DRIVER_MAJOR,                                          \
+	.minor = DRIVER_MINOR,                                          \
+	.patchlevel = DRIVER_PATCHLEVEL
+
+static const struct drm_driver
+driver_legacy_kms = {
+	.driver_features = DRIVER_GEM
+			 | DRIVER_SYNCOBJ
+			 | DRIVER_SYNCOBJ_TIMELINE
+			 | DRIVER_MODESET
+			 | DRIVER_RENDER,
+	NOUVEAU_DRIVER_OPS,
+};
 
-	.name = DRIVER_NAME,
-	.desc = DRIVER_DESC,
-	.major = DRIVER_MAJOR,
-	.minor = DRIVER_MINOR,
-	.patchlevel = DRIVER_PATCHLEVEL,
+static const struct drm_driver
+driver_atomic_kms = {
+	.driver_features = DRIVER_GEM
+			 | DRIVER_SYNCOBJ
+			 | DRIVER_SYNCOBJ_TIMELINE
+			 | DRIVER_MODESET
+			 | DRIVER_RENDER
+			 | DRIVER_ATOMIC,
+	NOUVEAU_DRIVER_OPS,
 };
 
 static struct pci_device_id
@@ -1457,7 +1476,7 @@ 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;
@@ -1482,9 +1501,6 @@ nouveau_drm_init(void)
 {
 	int ret;
 
-	driver_pci = driver_stub;
-	driver_platform = driver_stub;
-
 	nouveau_display_options();
 
 	if (nouveau_modeset == -1) {
-- 
2.55.0