drm/tegra: Allocate per-engine channel in core code

To avoid code duplication, allocate the per-engine shared channel in
the core code instead. This is the usual channel that all jobs are
submitted to when MLOCKing is not in use. Once MLOCKs are implemented
on Host1x side, we can also update this to avoid allocating a shared
channel when MLOCKs are enabled.

Signed-off-by: Mikko Perttunen <[e-mail]>
Signed-off-by: Thierry Reding <[e-mail]>

drivers/gpu/drm/tegra/drm.c

···
 int tegra_drm_register_client(struct tegra_drm *tegra,
 			      struct tegra_drm_client *client)
 {
+	/*
+	 * When MLOCKs are implemented, change to allocate a shared channel
+	 * only when MLOCKs are disabled.
+	 */
+	client->shared_channel = host1x_channel_request(&client->base);
+	if (!client->shared_channel)
+		return -EBUSY;
+
 	mutex_lock(&tegra->clients_lock);
 	list_add_tail(&client->list, &tegra->clients);
 	client->drm = tegra;
···
 	list_del_init(&client->list);
 	client->drm = NULL;
 	mutex_unlock(&tegra->clients_lock);
+
+	if (client->shared_channel)
+		host1x_channel_put(client->shared_channel);
 
 	return 0;
 }

drivers/gpu/drm/tegra/drm.h

···
 	struct host1x_client base;
 	struct list_head list;
 	struct tegra_drm *drm;
+	struct host1x_channel *shared_channel;
 
+	/* Set by driver */
 	unsigned int version;
 	const struct tegra_drm_client_ops *ops;
 };