[PATCH 2/5] drm/nouveau: Do not implement mode_set_base_atomic callback

Thomas Zimmermann
2025-11-25T13:06:48Z

Remove the implementation of the CRTC helper mode_set_base_atomic
from nouveau. It pretends to provide mode setting for kdb debugging,
but has been broken for some time.

Kdb output has been supported only for non-atomic mode setting since
commit 9c79e0b1d096 ("drm/fb-helper: Give up on kgdb for atomic drivers")
from 2017.

While nouveau provides non-atomic mode setting for some devices, kdb
assumes that the GEM buffer object is at a fixed location in video
memory. This has not been the case since
commit 4a16dd9d18a0 ("drm/nouveau/kms: switch to drm fbdev helpers")
from 2022. Fbdev-ttm helpers use a shadow buffer with a movable GEM
buffer object. Triggering kdb does therefore not update the display.

Hence remove the whole kdb support from nouveau.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
---
drivers/gpu/drm/nouveau/dispnv04/crtc.c | 24 ++++--------------------
1 file changed, 4 insertions(+), 20 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/dispnv04/crtc.c b/drivers/gpu/drm/nouveau/dispnv04/crtc.c
index c063756eaea3..80493224eb6c 100644
--- a/drivers/gpu/drm/nouveau/dispnv04/crtc.c
+++ b/drivers/gpu/drm/nouveau/dispnv04/crtc.c
@@ -837,7 +837,7 @@ nv_crtc_gamma_set(struct drm_crtc *crtc, u16 *r, u16 *g, u16 *b,
static int
nv04_crtc_do_mode_set_base(struct drm_crtc *crtc,
struct drm_framebuffer *passed_fb,
- int x, int y, bool atomic)
+ int x, int y)
{
struct nouveau_crtc *nv_crtc = nouveau_crtc(crtc);
struct drm_device *dev = crtc->dev;
@@ -850,19 +850,12 @@ nv04_crtc_do_mode_set_base(struct drm_crtc *crtc,
NV_DEBUG(drm, "index %d\n", nv_crtc->index);

/* no fb bound */
- if (!atomic && !crtc->primary->fb) {
+ if (!crtc->primary->fb) {
NV_DEBUG(drm, "No FB bound\n");
return 0;
}

- /* If atomic, we want to switch to the fb we were passed, so
- * now we update pointers to do that.
- */
- if (atomic) {
- drm_fb = passed_fb;
- } else {
- drm_fb = crtc->primary->fb;
- }
+ drm_fb = crtc->primary->fb;

nvbo = nouveau_gem_object(drm_fb->obj[0]);
nv_crtc->fb.offset = nvbo->offset;
@@ -920,15 +913,7 @@ nv04_crtc_mode_set_base(struct drm_crtc *crtc, int x, int y,
int ret = nv_crtc_swap_fbs(crtc, old_fb);
if (ret)
return ret;
- return nv04_crtc_do_mode_set_base(crtc, old_fb, x, y, false);
-}
-
-static int
-nv04_crtc_mode_set_base_atomic(struct drm_crtc *crtc,
- struct drm_framebuffer *fb,
- int x, int y, enum mode_set_atomic state)
-{
- return nv04_crtc_do_mode_set_base(crtc, fb, x, y, true);
+ return nv04_crtc_do_mode_set_base(crtc, old_fb, x, y);
}

static void nv04_cursor_upload(struct drm_device *dev, struct nouveau_bo *src,
@@ -1274,7 +1259,6 @@ static const struct drm_crtc_helper_funcs nv04_crtc_helper_funcs = {
.commit = nv_crtc_commit,
.mode_set = nv_crtc_mode_set,
.mode_set_base = nv04_crtc_mode_set_base,
- .mode_set_base_atomic = nv04_crtc_mode_set_base_atomic,
.disable = nv_crtc_disable,
.get_scanout_position = nouveau_display_scanoutpos,
};
--
2.51.1