gpu: host1x: Fix memory leak of device names

The device names allocated by dev_set_name() need be freed
before module unloading, but they can not be freed because
the kobject's refcount which was set in device_initialize()
has not be decreased to 0.

As comment of device_add() says, if it fails, use only
put_device() drop the refcount, then the name will be
freed in kobejct_cleanup().

device_del() and put_device() can be replaced with
device_unregister(), so call it to unregister the added
successfully devices, and just call put_device() to the
not added device.

Add a release() function to device to avoid null release()
function WARNING in device_release(), it's empty, because
the context devices are freed together in
host1x_memory_context_list_free().

Fixes: 8aa5bcb6 ("gpu: host1x: Add context device management code")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Mikko Perttunen <mperttunen@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/host1x/context.c

@@ -13,6 +13,11 @@
 #include "context.h"
 #include "dev.h"
 
+static void host1x_memory_context_release(struct device *dev)
+{
+	/* context device is freed in host1x_memory_context_list_free() */
+}
+
 int host1x_memory_context_list_init(struct host1x *host1x)
 {
 	struct host1x_memory_context_list *cdl = &host1x->context_list;
@@ -51,36 +56,38 @@ int host1x_memory_context_list_init(struct host1x *host1x)
 		dev_set_name(&ctx->dev, "host1x-ctx.%d", i);
 		ctx->dev.bus = &host1x_context_device_bus_type;
 		ctx->dev.parent = host1x->dev;
+		ctx->dev.release = host1x_memory_context_release;
 
 		dma_set_max_seg_size(&ctx->dev, UINT_MAX);
 
 		err = device_add(&ctx->dev);
 		if (err) {
 			dev_err(host1x->dev, "could not add context device %d: %d\n", i, err);
-			goto del_devices;
+			put_device(&ctx->dev);
+			goto unreg_devices;
 		}
 
 		err = of_dma_configure_id(&ctx->dev, node, true, &i);
 		if (err) {
 			dev_err(host1x->dev, "IOMMU configuration failed for context device %d: %d\n",
 				i, err);
-			device_del(&ctx->dev);
-			goto del_devices;
+			device_unregister(&ctx->dev);
+			goto unreg_devices;
 		}
 
 		if (!tegra_dev_iommu_get_stream_id(&ctx->dev, &ctx->stream_id) ||
 		    !device_iommu_mapped(&ctx->dev)) {
 			dev_err(host1x->dev, "Context device %d has no IOMMU!\n", i);
-			device_del(&ctx->dev);
-			goto del_devices;
+			device_unregister(&ctx->dev);
+			goto unreg_devices;
 		}
 	}
 
 	return 0;
 
-del_devices:
+unreg_devices:
 	while (i--)
-		device_del(&cdl->devs[i].dev);
+		device_unregister(&cdl->devs[i].dev);
 
 	kfree(cdl->devs);
 	cdl->devs = NULL;
@@ -94,7 +101,7 @@ void host1x_memory_context_list_free(struct host1x_memory_context_list *cdl)
 	unsigned int i;
 
 	for (i = 0; i < cdl->len; i++)
-		device_del(&cdl->devs[i].dev);
+		device_unregister(&cdl->devs[i].dev);
 
 	kfree(cdl->devs);
 	cdl->len = 0;