Since the commit mentioned down below, it looks like we've been triggering
this WARN_ON():

  [   31.477009] ------------[ cut here ]------------
  [   31.477012] [PLANE:66:curs-0] pixel format with alpha exposed but
  blend mode not setup
  [   31.477014] WARNING: drivers/gpu/drm/drm_mode_config.c:872 at
  drm_mode_config_validate+0x38c/0x4c0, CPU#1: modprobe/1264
  [   31.477125] CPU: 1 UID: 0 PID: 1264 Comm: modprobe Not tainted
  7.2.0-rc2Lyude-Test+ #1 PREEMPT(lazy)
  [   31.477129] Hardware name: Micro-Star International Co., Ltd.
  MS-7A39/A320M GAMING PRO (MS-7A39), BIOS 1.M4 05/10/2023
  [   31.477132] RIP: 0010:drm_mode_config_validate+0x394/0x4c0
  [   31.477136] Code: 41 3b 9e 80 00 00 00 73 bd 49 8b 46 78 8b 3c 98 e8
  c1 3d ff ff 80 78 14 00 74 e1 48 8d 3d 64 e6 e7 01 49 8b 56 18 41 8b 76
  50 <67> 48 0f b9 3a 49 8b 46 08 4c 8d 70 f8 49 39 c5 75 97 8b 95 b8 02
  [   31.477139] RSP: 0018:ffffd48e053bb7f8 EFLAGS: 00010202
  [   31.477143] RAX: ffffffffaf1da9c0 RBX: 0000000000000000 RCX: 0000000000000034
  [   31.477145] RDX: ffff8cd883c1feb0 RSI: 0000000000000042 RDI: ffffffffb069f840
  [   31.477148] RBP: ffff8cd88ea3d800 R08: 0000000034325241 R09: ffff8cd88ea3dac0
  [   31.477150] R10: fffffaf5c4043600 R11: ffff8cd88004f600 R12: 0000000000000001
  [   31.477152] R13: ffff8cd88ea3da90 R14: ffff8cd88b9ec038 R15: ffff8cd88ea3dab0
  [   31.477154] FS:  00007fb934898780(0000) GS:ffff8cd9f3a6a000(0000) knlGS:0000000000000000
  [   31.477157] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  [   31.477160] CR2: 0000555efff79520 CR3: 0000000122cd5000 CR4: 00000000003506f0
  [   31.477162] Call Trace:
  [   31.477165]  <TASK>
  [   31.477168]  ? nouveau_hwmon_init+0x2d6/0x330 [nouveau]
  [   31.477346]  drm_dev_register+0x19d/0x270
  [   31.477352]  nouveau_drm_device_init+0x17a/0x230 [nouveau]
  [   31.477523]  nouveau_drm_probe+0x13d/0x1e0 [nouveau]
  [   31.477690]  local_pci_probe+0x3e/0x90
  [   31.477697]  pci_call_probe+0x59/0x190
  [   31.477702]  ? srso_return_thunk+0x5/0x5f
  [   31.477706]  ? pci_match_device+0x15a/0x180
  [   31.477710]  ? pci_assign_irq+0x2d/0x160
  [   31.477714]  pci_device_probe+0x95/0x160
  [   31.477719]  call_driver_probe+0x26/0x100
  [   31.477724]  ? driver_sysfs_add+0x59/0xd0
  [   31.477738]  really_probe+0xcc/0x2c0
  [   31.477743]  ? srso_return_thunk+0x5/0x5f
  [   31.477749]  __driver_probe_device+0x85/0x170
  [   31.477754]  driver_probe_device+0x1f/0x90
  [   31.477760]  ? __pfx___driver_attach+0x10/0x10
  [   31.477766]  __driver_attach+0xcb/0x210
  [   31.477772]  bus_for_each_dev+0x85/0xd0
  [   31.477779]  bus_add_driver+0x13e/0x220
  [   31.477786]  ? __pfx_init_module+0x10/0x10 [nouveau]
  [   31.477979]  driver_register+0x75/0xe0
  [   31.477984]  ? srso_return_thunk+0x5/0x5f
  [   31.477990]  nouveau_drm_init+0x8b/0xff0 [nouveau]
  [   31.478192]  do_one_initcall+0x5d/0x300
  [   31.478204]  do_init_module+0x86/0x290
  [   31.478212]  init_module_from_file+0xd8/0x140
  [   31.478223]  idempotent_init_module+0x114/0x310
  [   31.478233]  __x64_sys_finit_module+0x71/0xe0
  [   31.478238]  do_syscall_64+0xe2/0x630
  [   31.478252]  ? srso_return_thunk+0x5/0x5f
  [   31.478257]  ? vfs_read+0x165/0x390
  [   31.478267]  ? srso_return_thunk+0x5/0x5f
  [   31.478271]  ? srso_return_thunk+0x5/0x5f
  [   31.478276]  ? switch_fpu_return+0x52/0xe0
  [   31.478282]  ? srso_return_thunk+0x5/0x5f
  [   31.478286]  ? arch_exit_to_user_mode_prepare.isra.0+0x7e/0x90
  [   31.478292]  ? srso_return_thunk+0x5/0x5f
  [   31.478296]  ? do_syscall_64+0x11f/0x630
  [   31.478301]  ? srso_return_thunk+0x5/0x5f
  [   31.478305]  ? arch_exit_to_user_mode_prepare.isra.0+0x7e/0x90
  [   31.478310]  ? srso_return_thunk+0x5/0x5f
  [   31.478314]  ? do_syscall_64+0x11f/0x630
  [   31.478320]  ? srso_return_thunk+0x5/0x5f
  [   31.478324]  ? arch_exit_to_user_mode_prepare.isra.0+0x7e/0x90
  [   31.478329]  ? srso_return_thunk+0x5/0x5f
  [   31.478334]  ? srso_return_thunk+0x5/0x5f
  [   31.478338]  ? do_syscall_64+0x99/0x630
  [   31.478343]  ? exc_page_fault+0x82/0x1c0
  [   31.478350]  entry_SYSCALL_64_after_hwframe+0x76/0x7e
  [   31.478355] RIP: 0033:0x7fb93410030d
  [   31.478372] Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa
  48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f
  05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d c3 5a 0f 00 f7 d8 64 89 01 48
  [   31.478375] RSP: 002b:00007ffc587ce738 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
  [   31.478381] RAX: ffffffffffffffda RBX: 0000562f5fb3da60 RCX: 00007fb93410030d
  [   31.478385] RDX: 0000000000000000 RSI: 0000562f5fb40590 RDI: 000000000000000d
  [   31.478388] RBP: 00007ffc587ce7d0 R08: 0000000000000000 R09: 0000000000000000
  [   31.478391] R10: 0000000000000000 R11: 0000000000000246 R12: 0000562f5fb40590
  [   31.478394] R13: 0000000000040000 R14: 0000562f5fb3db80 R15: 0000000000000009
  [   31.478404]  </TASK>
  [   31.478407] ---[ end trace 0000000000000000 ]---

Fix it by making sure we unconditionally call
drm_plane_create_blend_mode_property for all types of wndws, including
those (such as cursors) without a blend_set function.

Fixes: 860e748bddcc ("drm: ensure blend mode supported if pixel format with alpha exposed")
Signed-off-by: Lyude Paul <lyude@redhat.com>
---
 drivers/gpu/drm/nouveau/dispnv50/wndw.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/dispnv50/wndw.c b/drivers/gpu/drm/nouveau/dispnv50/wndw.c
index 2635458d52acc..9ec06dceceef5 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/wndw.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/wndw.c
@@ -860,6 +860,7 @@ nv50_wndw_new_(const struct nv50_wndw_func *func, struct drm_device *dev,
 	struct nv50_disp *disp = nv50_disp(dev);
 	struct nv50_wndw *wndw;
 	const u64 *format_modifiers;
+	unsigned int blend_modes = BIT(DRM_MODE_BLEND_PIXEL_NONE);
 	int nformat;
 	int ret;
 
@@ -909,12 +910,7 @@ nv50_wndw_new_(const struct nv50_wndw_func *func, struct drm_device *dev,
 		if (ret)
 			return ret;
 
-		ret = drm_plane_create_blend_mode_property(&wndw->plane,
-				BIT(DRM_MODE_BLEND_PIXEL_NONE) |
-				BIT(DRM_MODE_BLEND_PREMULTI) |
-				BIT(DRM_MODE_BLEND_COVERAGE));
-		if (ret)
-			return ret;
+		blend_modes |= BIT(DRM_MODE_BLEND_PREMULTI) | BIT(DRM_MODE_BLEND_COVERAGE);
 	} else {
 		ret = drm_plane_create_zpos_immutable_property(&wndw->plane,
 				nv50_wndw_zpos_default(&wndw->plane));
@@ -922,6 +918,10 @@ nv50_wndw_new_(const struct nv50_wndw_func *func, struct drm_device *dev,
 			return ret;
 	}
 
+	ret = drm_plane_create_blend_mode_property(&wndw->plane, blend_modes);
+	if (ret)
+		return ret;
+
 	return 0;
 }
 
-- 
2.55.0