drm/etnaviv: allocate unique ID per drm_file

Allows to easily track if several fd are pointing to the same
execution context due to being dup'ed.

Signed-off-by: Lucas Stach <[e-mail]>
Reviewed-by: Philipp Zabel <[e-mail]>

drivers/gpu/drm/etnaviv/etnaviv_drv.c

···
 	if (!ctx)
 		return -ENOMEM;
 
+	ret = xa_alloc_cyclic(&priv->active_contexts, &ctx->id, ctx,
+			      xa_limit_32b, &priv->next_context_id, GFP_KERNEL);
+	if (ret < 0)
+		goto out_free;
+
 	ctx->mmu = etnaviv_iommu_context_init(priv->mmu_global,
 					      priv->cmdbuf_suballoc);
 	if (!ctx->mmu) {
···
 	}
 
 	etnaviv_iommu_context_put(ctx->mmu);
+
+	xa_erase(&priv->active_contexts, ctx->id);
 
 	kfree(ctx);
 }
···
 
 	dma_set_max_seg_size(dev, SZ_2G);
 
+	xa_init_flags(&priv->active_contexts, XA_FLAGS_ALLOC);
+
 	mutex_init(&priv->gem_lock);
 	INIT_LIST_HEAD(&priv->gem_list);
 	priv->num_gpus = 0;
···
 	component_unbind_all(dev, drm);
 
 	etnaviv_cmdbuf_suballoc_destroy(priv->cmdbuf_suballoc);
+
+	xa_destroy(&priv->active_contexts);
 
 	drm->dev_private = NULL;
 	kfree(priv);

drivers/gpu/drm/etnaviv/etnaviv_drv.h

···
 #define ETNAVIV_SOFTPIN_START_ADDRESS	SZ_4M /* must be >= SUBALLOC_SIZE */
 
 struct etnaviv_file_private {
+	int id;
 	struct etnaviv_iommu_context	*mmu;
 	struct drm_sched_entity		sched_entity[ETNA_MAX_PIPES];
 };
···
 
 	struct etnaviv_cmdbuf_suballoc *cmdbuf_suballoc;
 	struct etnaviv_iommu_global *mmu_global;
+
+	struct xarray active_contexts;
+	u32 next_context_id;
 
 	/* list of GEM objects: */
 	struct mutex gem_lock;