swiotlb: simplify debugfs setup

Debugfs functions are already stubbed out for !CONFIG_DEBUG_FS, so we
can remove most of the #ifdefs, just keeping one to manually optimise
away the initcall when it would do nothing. We can also simplify the
code itself by factoring out the directory creation and realising that
the global io_tlb_default_mem now makes debugfs_dir redundant.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

Author: rmurphy-arm

kernel/dma/swiotlb.c

@@ -36,9 +36,7 @@
 #include <linux/scatterlist.h>
 #include <linux/cc_platform.h>
 #include <linux/set_memory.h>
-#ifdef CONFIG_DEBUG_FS
 #include <linux/debugfs.h>
-#endif
 #ifdef CONFIG_DMA_RESTRICTED_POOL
 #include <linux/io.h>
 #include <linux/of.h>
@@ -756,47 +754,29 @@ bool is_swiotlb_active(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(is_swiotlb_active);
 
-#ifdef CONFIG_DEBUG_FS
-static struct dentry *debugfs_dir;
-
-static void swiotlb_create_debugfs_files(struct io_tlb_mem *mem)
+static void swiotlb_create_debugfs_files(struct io_tlb_mem *mem,
+					 const char *dirname)
 {
+	mem->debugfs = debugfs_create_dir(dirname, io_tlb_default_mem.debugfs);
+	if (!mem->nslabs)
+		return;
+
 	debugfs_create_ulong("io_tlb_nslabs", 0400, mem->debugfs, &mem->nslabs);
 	debugfs_create_ulong("io_tlb_used", 0400, mem->debugfs, &mem->used);
 }
 
-static int __init swiotlb_create_default_debugfs(void)
+static int __init __maybe_unused swiotlb_create_default_debugfs(void)
 {
-	struct io_tlb_mem *mem = &io_tlb_default_mem;
-
-	debugfs_dir = debugfs_create_dir("swiotlb", NULL);
-	if (mem->nslabs) {
-		mem->debugfs = debugfs_dir;
-		swiotlb_create_debugfs_files(mem);
-	}
+	swiotlb_create_debugfs_files(&io_tlb_default_mem, "swiotlb");
 	return 0;
 }
 
+#ifdef CONFIG_DEBUG_FS
 late_initcall(swiotlb_create_default_debugfs);
-
 #endif
 
 #ifdef CONFIG_DMA_RESTRICTED_POOL
 
-#ifdef CONFIG_DEBUG_FS
-static void rmem_swiotlb_debugfs_init(struct reserved_mem *rmem)
-{
-	struct io_tlb_mem *mem = rmem->priv;
-
-	mem->debugfs = debugfs_create_dir(rmem->name, debugfs_dir);
-	swiotlb_create_debugfs_files(mem);
-}
-#else
-static void rmem_swiotlb_debugfs_init(struct reserved_mem *rmem)
-{
-}
-#endif
-
 struct page *swiotlb_alloc(struct device *dev, size_t size)
 {
 	struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
@@ -858,7 +838,7 @@ static int rmem_swiotlb_device_init(struct reserved_mem *rmem,
 
 		rmem->priv = mem;
 
-		rmem_swiotlb_debugfs_init(rmem);
+		swiotlb_create_debugfs_files(mem, rmem->name);
 	}
 
 	dev->dma_io_tlb_mem = mem;