[PATCH] drm/nouveau/kms/nv50-: Program notifier offset before requesting disp caps

[Lyude Paul <lyude@redhat.com>]

Not entirely sure why this never came up when I originally tested this
(maybe some BIOSes already have this setup?) but the ->caps_init vfunc
appears to cause the display engine to throw an exception on driver
init, at least on my ThinkPad P72:

nouveau 0000:01:00.0: disp: chid 0 mthd 008c data 00000000 0000508c 0000102b

This is magic nvidia speak for "You need to have the DMA notifier offset
programmed before you can call NV507D_GET_CAPABILITIES." So, let's fix
this by doing that.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Fixes: 4a2cb4181b07 ("drm/nouveau/kms/nv50-: Probe SOR and PIOR caps for DP interlacing support")
Cc: <stable@vger.kernel.org> # v5.8+
---
 drivers/gpu/drm/nouveau/dispnv50/core507d.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/dispnv50/core507d.c b/drivers/gpu/drm/nouveau/dispnv50/core507d.c
index ad1f09a143aa4..c984080ce99f2 100644
--- a/drivers/gpu/drm/nouveau/dispnv50/core507d.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/core507d.c
@@ -80,11 +80,19 @@ core507d_caps_init(struct nouveau_drm *drm, struct nv50_disp *disp)
 	struct nvif_push *push = disp->core->chan.push;
 	int ret;
 
-	if ((ret = PUSH_WAIT(push, 2)))
+	if ((ret = PUSH_WAIT(push, 4)))
 		return ret;
 
+	PUSH_MTHD(push, NV507D, SET_NOTIFIER_CONTROL,
+		  NVDEF(NV507D, SET_NOTIFIER_CONTROL, MODE, WRITE) |
+		  NVVAL(NV507D, SET_NOTIFIER_CONTROL, OFFSET, NV50_DISP_CORE_NTFY >> 2) |
+		  NVDEF(NV507D, SET_NOTIFIER_CONTROL, NOTIFY, ENABLE));
 	PUSH_MTHD(push, NV507D, GET_CAPABILITIES, 0x00000000);
-	return PUSH_KICK(push);
+	ret = PUSH_KICK(push);
+	if (ret)
+		return ret;
+
+	return 0;
 }
 
 int
-- 
2.26.2