drm/vmwgfx: Implement dma_fence_ops properly

vmwgfx's fencing predates dma_fence and as a result dma_fence_ops was never
properly implemented, especially with respect to enabling signaling.

Because of this dma_fence callbacks don't work properly. This change
implements enable_signaling properly so that dma_fence callbacks now
work as expected.

It also removes vmwgfx's custom implementation of fence callbacks
and removes vmwgfx's custom dma_fence_ops::wait function which is no
longer necessary now that enable_signaling works.

Signed-off-by: Ian Forbes <ian.forbes@broadcom.com>
Signed-off-by: Zack Rusin <zack.rusin@broadcom.com>
Link: https://lore.kernel.org/r/20250530183510.733175-2-ian.forbes@broadcom.com

Author: en4bz

drivers/gpu/drm/vmwgfx/vmwgfx_drv.h

@@ -1006,14 +1006,14 @@ extern int vmw_fallback_wait(struct vmw_private *dev_priv,
 			     uint32_t seqno,
 			     bool interruptible,
 			     unsigned long timeout);
-extern void vmw_seqno_waiter_add(struct vmw_private *dev_priv);
-extern void vmw_seqno_waiter_remove(struct vmw_private *dev_priv);
-extern void vmw_goal_waiter_add(struct vmw_private *dev_priv);
-extern void vmw_goal_waiter_remove(struct vmw_private *dev_priv);
-extern void vmw_generic_waiter_add(struct vmw_private *dev_priv, u32 flag,
-				   int *waiter_count);
-extern void vmw_generic_waiter_remove(struct vmw_private *dev_priv,
-				      u32 flag, int *waiter_count);
+bool vmw_seqno_waiter_add(struct vmw_private *dev_priv);
+bool vmw_seqno_waiter_remove(struct vmw_private *dev_priv);
+bool vmw_goal_waiter_add(struct vmw_private *dev_priv);
+bool vmw_goal_waiter_remove(struct vmw_private *dev_priv);
+bool vmw_generic_waiter_add(struct vmw_private *dev_priv, u32 flag,
+			    int *waiter_count);
+bool vmw_generic_waiter_remove(struct vmw_private *dev_priv,
+			       u32 flag, int *waiter_count);
 
 /**
  * Kernel modesetting - vmwgfx_kms.c

drivers/gpu/drm/vmwgfx/vmwgfx_execbuf.c

@@ -4067,23 +4067,6 @@ static int vmw_execbuf_tie_context(struct vmw_private *dev_priv,
 	return 0;
 }
 
-/*
- * DMA fence callback to remove a seqno_waiter
- */
-struct seqno_waiter_rm_context {
-	struct dma_fence_cb base;
-	struct vmw_private *dev_priv;
-};
-
-static void seqno_waiter_rm_cb(struct dma_fence *f, struct dma_fence_cb *cb)
-{
-	struct seqno_waiter_rm_context *ctx =
-		container_of(cb, struct seqno_waiter_rm_context, base);
-
-	vmw_seqno_waiter_remove(ctx->dev_priv);
-	kfree(ctx);
-}
-
 int vmw_execbuf_process(struct drm_file *file_priv,
 			struct vmw_private *dev_priv,
 			void __user *user_commands, void *kernel_commands,
@@ -4264,15 +4247,6 @@ int vmw_execbuf_process(struct drm_file *file_priv,
 		} else {
 			/* Link the fence with the FD created earlier */
 			fd_install(out_fence_fd, sync_file->file);
-			struct seqno_waiter_rm_context *ctx =
-				kmalloc(sizeof(*ctx), GFP_KERNEL);
-			ctx->dev_priv = dev_priv;
-			vmw_seqno_waiter_add(dev_priv);
-			if (dma_fence_add_callback(&fence->base, &ctx->base,
-						   seqno_waiter_rm_cb) < 0) {
-				vmw_seqno_waiter_remove(dev_priv);
-				kfree(ctx);
-			}
 		}
 	}