dmaengine: Create debug directories for DMA devices

Create a placeholder directory for each registered DMA device.

DMA drivers can use the dmaengine_get_debugfs_root() call to get their
debugfs root and can populate with custom files to aim debugging.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Link: https://lore.kernel.org/r/20200306142839.17910-4-peter.ujfalusi@ti.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/dmaengine.c

@@ -62,6 +62,22 @@ static long dmaengine_ref_count;
 #ifdef CONFIG_DEBUG_FS
 #include <linux/debugfs.h>
 
+static struct dentry *rootdir;
+
+static void dmaengine_debug_register(struct dma_device *dma_dev)
+{
+	dma_dev->dbg_dev_root = debugfs_create_dir(dev_name(dma_dev->dev),
+						   rootdir);
+	if (IS_ERR(dma_dev->dbg_dev_root))
+		dma_dev->dbg_dev_root = NULL;
+}
+
+static void dmaengine_debug_unregister(struct dma_device *dma_dev)
+{
+	debugfs_remove_recursive(dma_dev->dbg_dev_root);
+	dma_dev->dbg_dev_root = NULL;
+}
+
 static void dmaengine_dbg_summary_show(struct seq_file *s,
 				       struct dma_device *dma_dev)
 {
@@ -107,7 +123,7 @@ DEFINE_SHOW_ATTRIBUTE(dmaengine_summary);
 
 static void __init dmaengine_debugfs_init(void)
 {
-	struct dentry *rootdir = debugfs_create_dir("dmaengine", NULL);
+	rootdir = debugfs_create_dir("dmaengine", NULL);
 
 	/* /sys/kernel/debug/dmaengine/summary */
 	debugfs_create_file("summary", 0444, rootdir, NULL,
@@ -115,6 +131,12 @@ static void __init dmaengine_debugfs_init(void)
 }
 #else
 static inline void dmaengine_debugfs_init(void) { }
+static inline int dmaengine_debug_register(struct dma_device *dma_dev)
+{
+	return 0;
+}
+
+static inline void dmaengine_debug_unregister(struct dma_device *dma_dev) { }
 #endif	/* DEBUG_FS */
 
 /* --- sysfs implementation --- */
@@ -1265,6 +1287,8 @@ int dma_async_device_register(struct dma_device *device)
 	dma_channel_rebalance();
 	mutex_unlock(&dma_list_mutex);
 
+	dmaengine_debug_register(device);
+
 	return 0;
 
 err_out:
@@ -1298,6 +1322,8 @@ void dma_async_device_unregister(struct dma_device *device)
 {
 	struct dma_chan *chan, *n;
 
+	dmaengine_debug_unregister(device);
+
 	list_for_each_entry_safe(chan, n, &device->channels, device_node)
 		__dma_async_device_channel_unregister(device, chan);
 

drivers/dma/dmaengine.h

@@ -182,4 +182,20 @@ dmaengine_desc_callback_valid(struct dmaengine_desc_callback *cb)
 struct dma_chan *dma_get_slave_channel(struct dma_chan *chan);
 struct dma_chan *dma_get_any_slave_channel(struct dma_device *device);
 
+#ifdef CONFIG_DEBUG_FS
+#include <linux/debugfs.h>
+
+static inline struct dentry *
+dmaengine_get_debugfs_root(struct dma_device *dma_dev) {
+	return dma_dev->dbg_dev_root;
+}
+#else
+struct dentry;
+static inline struct dentry *
+dmaengine_get_debugfs_root(struct dma_device *dma_dev)
+{
+	return NULL;
+}
+#endif /* CONFIG_DEBUG_FS */
+
 #endif

include/linux/dmaengine.h

@@ -902,6 +902,7 @@ struct dma_device {
 	/* debugfs support */
 #ifdef CONFIG_DEBUG_FS
 	void (*dbg_summary_show)(struct seq_file *s, struct dma_device *dev);
+	struct dentry *dbg_dev_root;
 #endif
 };