[PATCH v3 0/3] drm/nouveau: Fix WARN_ON() from missing blend modes

[PATCH v3 0/3] drm/nouveau: Fix WARN_ON() from missing blend modes

[Lyude Paul]

Recently a change went into the kernel to ensure that drivers which
expose color formats which have alpha channels. This would cause nouveau
to hit a WARN_ON when setting up cursors, since they do support blending
- but we never bothered trying to hook up the controls for it to
nouveau.

This fixes the issue by ensuring that nouveau always exposes a blend
mode for any planes with alpha channels, regardless of whether or not we
have control of the blend mode hooked up. If someone wants to add
control for this in the future as well, it should be fairly easy to hook
up with this.

Previous version:
	https://patchwork.freedesktop.org/api/1.0/series/170773/revisions/1/mbox/

Lyude Paul (3):
  drm/nouveau/kms/nv50-: Add .blend_modes to nv50_wndw_func
  drm/nouveau/kms/nv50-: Introduce nv50_wndw_default_state()
  drm/nouveau/kms/nv50-: Unconditionally create blend_mode prop for
    wndws

 drivers/gpu/drm/nouveau/dispnv50/base.h     |  6 ++++
 drivers/gpu/drm/nouveau/dispnv50/base507c.c |  1 +
 drivers/gpu/drm/nouveau/dispnv50/base827c.c |  1 +
 drivers/gpu/drm/nouveau/dispnv50/base907c.c |  1 +
 drivers/gpu/drm/nouveau/dispnv50/curs507a.c |  3 ++
 drivers/gpu/drm/nouveau/dispnv50/disp.c     |  4 +++
 drivers/gpu/drm/nouveau/dispnv50/wndw.c     | 40 +++++++++++++++++----
 drivers/gpu/drm/nouveau/dispnv50/wndw.h     | 11 ++++++
 drivers/gpu/drm/nouveau/dispnv50/wndwc37e.c |  1 +
 drivers/gpu/drm/nouveau/dispnv50/wndwc57e.c |  1 +
 drivers/gpu/drm/nouveau/dispnv50/wndwc67e.c |  1 +
 drivers/gpu/drm/nouveau/dispnv50/wndwca7e.c |  1 +
 12 files changed, 64 insertions(+), 7 deletions(-)


base-commit: b0a652436b892eb9a036a031b33099dca036faaa
-- 
2.55.0

[PATCH v3 1/3] drm/nouveau/kms/nv50-: Add .blend_modes to nv50_wndw_func

[Lyude Paul]

At the moment, we currently (incorrectly) only expose a blend property on
the plane if we have a nv50_wndw_func->blend_set function for the given
wndw type. But we need to expose a blend property for all types of planes
that can display color formats with an alpha channel.

Prepare for doing this by introducing a way of looking up the supported
blend modes for a type of wndw by introducing .blend_modes, which describes
all possible blending modes nouveau currently supports for a type of wndw.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Fixes: 860e748bddcc ("drm: ensure blend mode supported if pixel format with alpha exposed")

---
V3:
* Don't forget to specify .blend_modes for base.

 drivers/gpu/drm/nouveau/dispnv50/base.h     |  6 ++++++
 drivers/gpu/drm/nouveau/dispnv50/base507c.c |  1 +
 drivers/gpu/drm/nouveau/dispnv50/base827c.c |  1 +
 drivers/gpu/drm/nouveau/dispnv50/base907c.c |  1 +
 drivers/gpu/drm/nouveau/dispnv50/curs507a.c |  3 +++
 drivers/gpu/drm/nouveau/dispnv50/wndw.h     | 10 ++++++++++
 drivers/gpu/drm/nouveau/dispnv50/wndwc37e.c |  1 +
 drivers/gpu/drm/nouveau/dispnv50/wndwc57e.c |  1 +
 drivers/gpu/drm/nouveau/dispnv50/wndwc67e.c |  1 +
 drivers/gpu/drm/nouveau/dispnv50/wndwca7e.c |  1 +
 10 files changed, 26 insertions(+)

diff --git a/drivers/gpu/drm/nouveau/dispnv50/base.h b/drivers/gpu/drm/nouveau/dispnv50/base.h
index 085bd3aeb40b6..fbfd62d8fc798 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/base.h
+++ b/drivers/gpu/drm/nouveau/dispnv50/base.h
@@ -1,5 +1,7 @@
 #ifndef __NV50_KMS_BASE_H__
 #define __NV50_KMS_BASE_H__
+#include <drm/drm_blend.h>
+
 #include "wndw.h"
 
 int base507c_new(struct nouveau_drm *, int, s32, struct nv50_wndw **);
@@ -24,4 +26,8 @@ extern const struct nv50_wndw_func base907c;
 int base917c_new(struct nouveau_drm *, int, s32, struct nv50_wndw **);
 
 int nv50_base_new(struct nouveau_drm *, int head, struct nv50_wndw **);
+
+/* The only blend mode supported by base channels */
+#define BASE_BLEND_MODES BIT(DRM_MODE_BLEND_PIXEL_NONE)
+
 #endif
diff --git a/drivers/gpu/drm/nouveau/dispnv50/base507c.c b/drivers/gpu/drm/nouveau/dispnv50/base507c.c
index a431f6c5f6fa9..41b648ab3c5e5 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/base507c.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/base507c.c
@@ -297,6 +297,7 @@ base507c = {
 	.image_set = base507c_image_set,
 	.image_clr = base507c_image_clr,
 	.update = base507c_update,
+	.blend_modes = BASE_BLEND_MODES,
 };
 
 int
diff --git a/drivers/gpu/drm/nouveau/dispnv50/base827c.c b/drivers/gpu/drm/nouveau/dispnv50/base827c.c
index 4545cc5f3a14b..6c290324b4f3e 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/base827c.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/base827c.c
@@ -93,6 +93,7 @@ base827c = {
 	.image_set = base827c_image_set,
 	.image_clr = base507c_image_clr,
 	.update = base507c_update,
+	.blend_modes = BASE_BLEND_MODES,
 };
 
 int
diff --git a/drivers/gpu/drm/nouveau/dispnv50/base907c.c b/drivers/gpu/drm/nouveau/dispnv50/base907c.c
index 4a2d5a259e15b..a94d8350224b6 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/base907c.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/base907c.c
@@ -205,6 +205,7 @@ base907c = {
 	.image_set = base907c_image_set,
 	.image_clr = base507c_image_clr,
 	.update = base507c_update,
+	.blend_modes = BASE_BLEND_MODES,
 };
 
 int
diff --git a/drivers/gpu/drm/nouveau/dispnv50/curs507a.c b/drivers/gpu/drm/nouveau/dispnv50/curs507a.c
index 1a889139cb053..5f2ff40388e7f 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/curs507a.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/curs507a.c
@@ -29,6 +29,7 @@
 #include <nvhw/class/cl507a.h>
 
 #include <drm/drm_atomic_helper.h>
+#include <drm/drm_blend.h>
 #include <drm/drm_fourcc.h>
 
 bool
@@ -164,6 +165,8 @@ curs507a_wndw = {
 	.acquire = curs507a_acquire,
 	.release = curs507a_release,
 	.prepare = curs507a_prepare,
+	// TODO: Cursors also support premulti, but we haven't hooked it up anywhere yet.
+	.blend_modes = BIT(DRM_MODE_BLEND_COVERAGE),
 };
 
 int
diff --git a/drivers/gpu/drm/nouveau/dispnv50/wndw.h b/drivers/gpu/drm/nouveau/dispnv50/wndw.h
index 90d100514bef2..81af5c3369d4c 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/wndw.h
+++ b/drivers/gpu/drm/nouveau/dispnv50/wndw.h
@@ -1,6 +1,8 @@
 #ifndef __NV50_KMS_WNDW_H__
 #define __NV50_KMS_WNDW_H__
 #define nv50_wndw(p) container_of((p), struct nv50_wndw, plane)
+#include <drm/drm_blend.h>
+
 #include "disp.h"
 #include "atom.h"
 #include "lut.h"
@@ -74,6 +76,7 @@ struct nv50_wndw_func {
 	int (*image_clr)(struct nv50_wndw *);
 	int (*scale_set)(struct nv50_wndw *, struct nv50_wndw_atom *);
 	int (*blend_set)(struct nv50_wndw *, struct nv50_wndw_atom *);
+	unsigned int blend_modes;
 
 	int (*update)(struct nv50_wndw *, u32 *interlock);
 };
@@ -139,4 +142,11 @@ int wndwca7e_new(struct nouveau_drm *, enum drm_plane_type, int, s32,
 
 int nv50_wndw_new(struct nouveau_drm *, enum drm_plane_type, int index,
 		  struct nv50_wndw **);
+
+/* A set of blend modes supported by all wndws */
+#define WNDW_BLEND_MODES               \
+	  BIT(DRM_MODE_BLEND_COVERAGE) \
+	| BIT(DRM_MODE_BLEND_PREMULTI) \
+	| BIT(DRM_MODE_BLEND_PIXEL_NONE)
+
 #endif
diff --git a/drivers/gpu/drm/nouveau/dispnv50/wndwc37e.c b/drivers/gpu/drm/nouveau/dispnv50/wndwc37e.c
index 554c4f91f8bec..7ab4d532118ee 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/wndwc37e.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/wndwc37e.c
@@ -343,6 +343,7 @@ wndwc37e = {
 	.image_set = wndwc37e_image_set,
 	.image_clr = wndwc37e_image_clr,
 	.blend_set = wndwc37e_blend_set,
+	.blend_modes = WNDW_BLEND_MODES,
 	.update = wndwc37e_update,
 };
 
diff --git a/drivers/gpu/drm/nouveau/dispnv50/wndwc57e.c b/drivers/gpu/drm/nouveau/dispnv50/wndwc57e.c
index d1ca51aae58cd..e220f43b5bca7 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/wndwc57e.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/wndwc57e.c
@@ -231,6 +231,7 @@ wndwc57e = {
 	.image_set = wndwc57e_image_set,
 	.image_clr = wndwc37e_image_clr,
 	.blend_set = wndwc37e_blend_set,
+	.blend_modes = WNDW_BLEND_MODES,
 	.update = wndwc37e_update,
 };
 
diff --git a/drivers/gpu/drm/nouveau/dispnv50/wndwc67e.c b/drivers/gpu/drm/nouveau/dispnv50/wndwc67e.c
index 52af293c98f4a..580cf7abd8193 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/wndwc67e.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/wndwc67e.c
@@ -95,6 +95,7 @@ wndwc67e = {
 	.image_set = wndwc67e_image_set,
 	.image_clr = wndwc37e_image_clr,
 	.blend_set = wndwc37e_blend_set,
+	.blend_modes = WNDW_BLEND_MODES,
 	.update = wndwc37e_update,
 };
 
diff --git a/drivers/gpu/drm/nouveau/dispnv50/wndwca7e.c b/drivers/gpu/drm/nouveau/dispnv50/wndwca7e.c
index 2cec8cfbd5461..d65ec438b434f 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/wndwca7e.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/wndwca7e.c
@@ -231,6 +231,7 @@ wndwca7e = {
 	.image_set = wndwca7e_image_set,
 	.image_clr = wndwca7e_image_clr,
 	.blend_set = wndwc37e_blend_set,
+	.blend_modes = WNDW_BLEND_MODES,
 	.update = wndwc37e_update,
 };
 
-- 
2.55.0

[PATCH v3 2/3] drm/nouveau/kms/nv50-: Introduce nv50_wndw_default_state()

[Lyude Paul]

While we don't currently read-in the hardware state of planes, now that
we're about to start exposing blend properties for all planes that can
support alpha channels: We need to make sure that the initial atomic state
for a wndw always starts off with a supported value in pixel_blend_mode.

The easiest way to do this is to introduce a nv50_wndw_default_state()
function, and use it in nv50_display_read_hw_state() - and use that
function to enforce a valid value for pixel_blend_mode during driver
startup.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Fixes: 860e748bddcc ("drm: ensure blend mode supported if pixel format with alpha exposed")
---
V3:
* Fix incorrect bitmask checking in nv50_wndw_default_state()

 drivers/gpu/drm/nouveau/dispnv50/disp.c |  4 ++++
 drivers/gpu/drm/nouveau/dispnv50/wndw.c | 22 ++++++++++++++++++++++
 drivers/gpu/drm/nouveau/dispnv50/wndw.h |  1 +
 3 files changed, 27 insertions(+)

diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c
index 364227f5456f1..2c66e480b5116 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
@@ -2768,6 +2768,7 @@ nv50_display_read_hw_state(struct nouveau_drm *drm)
 {
 	struct drm_device *dev = drm->dev;
 	struct drm_encoder *encoder;
+	struct drm_plane *plane;
 	struct drm_modeset_acquire_ctx ctx;
 	struct nv50_disp *disp = nv50_disp(dev);
 	int ret;
@@ -2781,6 +2782,9 @@ nv50_display_read_hw_state(struct nouveau_drm *drm)
 		nv50_display_read_hw_or_state(dev, disp, nouveau_encoder(encoder));
 	}
 
+	drm_for_each_plane(plane, dev)
+		nv50_wndw_default_state(nv50_wndw(plane));
+
 	DRM_MODESET_LOCK_ALL_END(dev, ctx, ret);
 }
 
diff --git a/drivers/gpu/drm/nouveau/dispnv50/wndw.c b/drivers/gpu/drm/nouveau/dispnv50/wndw.c
index 2635458d52acc..dfa1ba45acd99 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/wndw.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/wndw.c
@@ -848,6 +848,28 @@ static const u64 nv50_cursor_format_modifiers[] = {
 	DRM_FORMAT_MOD_INVALID,
 };
 
+/*
+ * Setup defaults for the atomic wndw state
+ */
+void
+nv50_wndw_default_state(struct nv50_wndw *wndw)
+{
+	struct nv50_wndw_atom *armw = nv50_wndw_atom(wndw->plane.state);
+	const unsigned int blend_modes = wndw->func->blend_modes;
+
+	drm_modeset_lock_assert_held(&wndw->plane.mutex);
+
+	/* Ensure the plane's atomic state didn't default to a pixel_blend_mode we don't support */
+	if (blend_modes && (!(BIT(armw->state.pixel_blend_mode) & blend_modes))) {
+		if (blend_modes & BIT(DRM_MODE_BLEND_COVERAGE))
+			armw->state.pixel_blend_mode = DRM_MODE_BLEND_COVERAGE;
+		else if (blend_modes & BIT(DRM_MODE_BLEND_PREMULTI))
+			armw->state.pixel_blend_mode = DRM_MODE_BLEND_PREMULTI;
+		else if (blend_modes & BIT(DRM_MODE_BLEND_PIXEL_NONE))
+			armw->state.pixel_blend_mode = DRM_MODE_BLEND_PIXEL_NONE;
+	}
+}
+
 int
 nv50_wndw_new_(const struct nv50_wndw_func *func, struct drm_device *dev,
 	       enum drm_plane_type type, const char *name, int index,
diff --git a/drivers/gpu/drm/nouveau/dispnv50/wndw.h b/drivers/gpu/drm/nouveau/dispnv50/wndw.h
index 81af5c3369d4c..13f06b7b67611 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/wndw.h
+++ b/drivers/gpu/drm/nouveau/dispnv50/wndw.h
@@ -46,6 +46,7 @@ void nv50_wndw_flush_clr(struct nv50_wndw *, u32 *interlock, bool flush,
 			 struct nv50_wndw_atom *);
 void nv50_wndw_ntfy_enable(struct nv50_wndw *, struct nv50_wndw_atom *);
 int nv50_wndw_wait_armed(struct nv50_wndw *, struct nv50_wndw_atom *);
+void nv50_wndw_default_state(struct nv50_wndw *wndw);
 
 struct nv50_wndw_func {
 	int (*acquire)(struct nv50_wndw *, struct nv50_wndw_atom *asyw,
-- 
2.55.0

[PATCH v3 3/3] drm/nouveau/kms/nv50-: Unconditionally create blend_mode prop for wndws

[Lyude Paul]

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>

---
V2:
* Address Sashiko issue regarding pixel_blend_mode defaults
* The cursor uses DRM_MODE_BLEND_COVERAGE, not DRM_MODE_BLEND_PIXEL_NONE
* Start using the new blend_modes vtable entry

Signed-off-by: Lyude Paul <lyude@redhat.com>
---
 drivers/gpu/drm/nouveau/dispnv50/wndw.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/dispnv50/wndw.c b/drivers/gpu/drm/nouveau/dispnv50/wndw.c
index dfa1ba45acd99..15a322422f4e6 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/wndw.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/wndw.c
@@ -930,13 +930,6 @@ nv50_wndw_new_(const struct nv50_wndw_func *func, struct drm_device *dev,
 		ret = drm_plane_create_alpha_property(&wndw->plane);
 		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;
 	} else {
 		ret = drm_plane_create_zpos_immutable_property(&wndw->plane,
 				nv50_wndw_zpos_default(&wndw->plane));
@@ -944,6 +937,17 @@ nv50_wndw_new_(const struct nv50_wndw_func *func, struct drm_device *dev,
 			return ret;
 	}
 
+	/*
+	 * DRM requires that we have a blend mode property for any type of plane that exposes color
+	 * formats with an alpha channel. So do this, even if we don't actually have control for the
+	 * blend property hooked up with blend_set.
+	 */
+	if (func->blend_modes) {
+		ret = drm_plane_create_blend_mode_property(&wndw->plane, func->blend_modes);
+		if (ret)
+			return ret;
+	}
+
 	return 0;
 }
 
-- 
2.55.0

Re: [PATCH v3 0/3] drm/nouveau: Fix WARN_ON() from missing blend modes

[Dave Airlie]

On Tue, 21 Jul 2026 at 07:51, Lyude Paul <lyude@redhat.com> wrote:
>
> Recently a change went into the kernel to ensure that drivers which
> expose color formats which have alpha channels. This would cause nouveau
> to hit a WARN_ON when setting up cursors, since they do support blending
> - but we never bothered trying to hook up the controls for it to
> nouveau.
>
> This fixes the issue by ensuring that nouveau always exposes a blend
> mode for any planes with alpha channels, regardless of whether or not we
> have control of the blend mode hooked up. If someone wants to add
> control for this in the future as well, it should be fairly easy to hook
> up with this.
>
> Previous version:
>         https://patchwork.freedesktop.org/api/1.0/series/170773/revisions/1/mbox/

For the series,

Reviewed-by: Dave Airlie <airlied@redhat.com>

>
> Lyude Paul (3):
>   drm/nouveau/kms/nv50-: Add .blend_modes to nv50_wndw_func
>   drm/nouveau/kms/nv50-: Introduce nv50_wndw_default_state()
>   drm/nouveau/kms/nv50-: Unconditionally create blend_mode prop for
>     wndws
>
>  drivers/gpu/drm/nouveau/dispnv50/base.h     |  6 ++++
>  drivers/gpu/drm/nouveau/dispnv50/base507c.c |  1 +
>  drivers/gpu/drm/nouveau/dispnv50/base827c.c |  1 +
>  drivers/gpu/drm/nouveau/dispnv50/base907c.c |  1 +
>  drivers/gpu/drm/nouveau/dispnv50/curs507a.c |  3 ++
>  drivers/gpu/drm/nouveau/dispnv50/disp.c     |  4 +++
>  drivers/gpu/drm/nouveau/dispnv50/wndw.c     | 40 +++++++++++++++++----
>  drivers/gpu/drm/nouveau/dispnv50/wndw.h     | 11 ++++++
>  drivers/gpu/drm/nouveau/dispnv50/wndwc37e.c |  1 +
>  drivers/gpu/drm/nouveau/dispnv50/wndwc57e.c |  1 +
>  drivers/gpu/drm/nouveau/dispnv50/wndwc67e.c |  1 +
>  drivers/gpu/drm/nouveau/dispnv50/wndwca7e.c |  1 +
>  12 files changed, 64 insertions(+), 7 deletions(-)
>
>
> base-commit: b0a652436b892eb9a036a031b33099dca036faaa
> --
> 2.55.0
>