[PATCH 6.12 regression fix 2/2] drm/radeon: Revert: "use GEM references instead of TTMs"

[Hans de Goede]

Commit fd69ef05029f ("drm/radeon: use GEM references instead of TTMs")
causes a black screen at boot instead of showing the GDM login screen
(the system is still alive).

dmesg shows the following oops (abbreviated) when this happens:

[   29.315203] BUG: kernel NULL pointer dereference, address: 0000000000000000
[   29.315209] #PF: supervisor read access in kernel mode
[   29.315213] #PF: error_code(0x0000) - not-present page
[   29.315215] PGD 0 P4D 0
[   29.315220] Oops: Oops: 0000 [#1] PREEMPT SMP NOPTI
[   29.315225] CPU: 0 UID: 42 PID: 2253 Comm: Xwayland Tainted: G                   6.12.0-rc1+ #159
[   29.315232] Hardware name: Micro-Star International Co., Ltd. MS-7C95/B550M PRO-VDH WIFI (MS-7C95), BIOS 2.L0 07/18/2024
[   29.315234] RIP: 0010:drm_gem_object_free+0xc/0x20
[   29.315272] Call Trace:
[   29.315274]  <TASK>
[   29.315305]  ? asm_exc_page_fault+0x22/0x30
[   29.315315]  ? drm_gem_object_free+0xc/0x20
[   29.315320]  radeon_bo_unref+0x50/0x60 [radeon]
[   29.315337]  radeon_vm_fini+0x1ca/0x350 [radeon]
[   29.315356]  radeon_driver_postclose_kms+0x16d/0x180 [radeon]
[   29.315370]  drm_file_free+0x229/0x280
[   29.315377]  drm_release+0x5f/0xe0
[   29.315381]  __fput+0xfc/0x2c0

Revert the change to restore things back to working order.

Fixes: fd69ef05029f ("drm/radeon: use GEM references instead of TTMs")
Signed-off-by: Hans de Goede <hdegoede at redhat.com>
---
 drivers/gpu/drm/radeon/radeon_gem.c    | 2 +-
 drivers/gpu/drm/radeon/radeon_object.c | 7 +++++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/radeon/radeon_gem.c b/drivers/gpu/drm/radeon/radeon_gem.c
index 9735f4968b86..210e8d43bb23 100644
--- a/drivers/gpu/drm/radeon/radeon_gem.c
+++ b/drivers/gpu/drm/radeon/radeon_gem.c
@@ -88,7 +88,7 @@ static void radeon_gem_object_free(struct drm_gem_object *gobj)
 
 	if (robj) {
 		radeon_mn_unregister(robj);
-		ttm_bo_put(&robj->tbo);
+		radeon_bo_unref(&robj);
 	}
 }
 
diff --git a/drivers/gpu/drm/radeon/radeon_object.c b/drivers/gpu/drm/radeon/radeon_object.c
index d0e4b43d155c..450ff7daa46c 100644
--- a/drivers/gpu/drm/radeon/radeon_object.c
+++ b/drivers/gpu/drm/radeon/radeon_object.c
@@ -256,15 +256,18 @@ struct radeon_bo *radeon_bo_ref(struct radeon_bo *bo)
 	if (bo == NULL)
 		return NULL;
 
-	drm_gem_object_get(&bo->tbo.base);
+	ttm_bo_get(&bo->tbo);
 	return bo;
 }
 
 void radeon_bo_unref(struct radeon_bo **bo)
 {
+	struct ttm_buffer_object *tbo;
+
 	if ((*bo) == NULL)
 		return;
-	drm_gem_object_put(&(*bo)->tbo.base);
+	tbo = &((*bo)->tbo);
+	ttm_bo_put(tbo);
 	*bo = NULL;
 }
 
-- 
2.46.2