Commit e937cc1d authored by Peter Ujfalusi's avatar Peter Ujfalusi Committed by Vinod Koul
Browse files

dmaengine: Add basic debugfs support 



Via the /sys/kernel/debug/dmaengine/summary users can get information
about the DMA devices and the used channels.

Example output on am654-evm with audio using two channels and after running
dmatest on 4 channels:

dma0 (285c0000.dma-controller): number of channels: 96

dma1 (31150000.dma-controller): number of channels: 267
 dma1chan0    | 2b00000.mcasp:tx
 dma1chan1    | 2b00000.mcasp:rx
 dma1chan2    | in-use
 dma1chan3    | in-use
 dma1chan4    | in-use
 dma1chan5    | in-use

For slave channels we can show the device and the channel name a given
channel is requested.
For non slave devices the only information we know is that the channel is
in use.

DMA drivers can implement the optional dbg_summary_show callback to
provide controller specific information instead of the generic one.

It is easy to extend the generic dmaengine_summary_show() to print
additional information about the used channels.

I have taken the idea from gpiolib and clk subsystems.

Signed-off-by: default avatarPeter Ujfalusi <peter.ujfalusi@ti.com>
Link: https://lore.kernel.org/r/20200306142839.17910-2-peter.ujfalusi@ti.com


Signed-off-by: default avatarVinod Koul <vkoul@kernel.org>
parent 05fb8067

drivers/dma/dmaengine.c

+75 −1
Original line number Diff line number Diff line
@@ -58,6 +58,65 @@ static DEFINE_IDA(dma_ida); 
static LIST_HEAD(dma_device_list);

static long dmaengine_ref_count;



/* --- debugfs implementation --- */

#ifdef CONFIG_DEBUG_FS

#include <linux/debugfs.h>



static void dmaengine_dbg_summary_show(struct seq_file *s,

				       struct dma_device *dma_dev)

{

	struct dma_chan *chan;



	list_for_each_entry(chan, &dma_dev->channels, device_node) {

		if (chan->client_count) {

			seq_printf(s, " %-13s| %s", dma_chan_name(chan),

				   chan->dbg_client_name ?: "in-use");



			if (chan->router)

				seq_printf(s, " (via router: %s)\n",

					dev_name(chan->router->dev));

			else

				seq_puts(s, "\n");

		}

	}

}



static int dmaengine_summary_show(struct seq_file *s, void *data)

{

	struct dma_device *dma_dev = NULL;



	mutex_lock(&dma_list_mutex);

	list_for_each_entry(dma_dev, &dma_device_list, global_node) {

		seq_printf(s, "dma%d (%s): number of channels: %u\n",

			   dma_dev->dev_id, dev_name(dma_dev->dev),

			   dma_dev->chancnt);



		if (dma_dev->dbg_summary_show)

			dma_dev->dbg_summary_show(s, dma_dev);

		else

			dmaengine_dbg_summary_show(s, dma_dev);



		if (!list_is_last(&dma_dev->global_node, &dma_device_list))

			seq_puts(s, "\n");

	}

	mutex_unlock(&dma_list_mutex);



	return 0;

}

DEFINE_SHOW_ATTRIBUTE(dmaengine_summary);



static void __init dmaengine_debugfs_init(void)

{

	struct dentry *rootdir = debugfs_create_dir("dmaengine", NULL);



	/* /sys/kernel/debug/dmaengine/summary */

	debugfs_create_file("summary", 0444, rootdir, NULL,

			    &dmaengine_summary_fops);

}

#else

static inline void dmaengine_debugfs_init(void) { }

#endif	/* DEBUG_FS */



/* --- sysfs implementation --- */



#define DMA_SLAVE_NAME	"slave"
@@ -760,6 +819,11 @@ struct dma_chan *dma_request_chan(struct device *dev, const char *name) 
		return chan ? chan : ERR_PTR(-EPROBE_DEFER);



found:

#ifdef CONFIG_DEBUG_FS

	chan->dbg_client_name = kasprintf(GFP_KERNEL, "%s:%s", dev_name(dev),

					  name);

#endif



	chan->name = kasprintf(GFP_KERNEL, "dma:%s", name);

	if (!chan->name)

		return chan;
@@ -837,6 +901,11 @@ void dma_release_channel(struct dma_chan *chan) 
		chan->name = NULL;

		chan->slave = NULL;

	}



#ifdef CONFIG_DEBUG_FS

	kfree(chan->dbg_client_name);

	chan->dbg_client_name = NULL;

#endif

	mutex_unlock(&dma_list_mutex);

}

EXPORT_SYMBOL_GPL(dma_release_channel);
@@ -1559,6 +1628,11 @@ static int __init dma_bus_init(void) 


	if (err)

		return err;

	return class_register(&dma_devclass);



	err = class_register(&dma_devclass);

	if (!err)

		dmaengine_debugfs_init();



	return err;

}

arch_initcall(dma_bus_init);

include/linux/dmaengine.h

+12 −1
Original line number Diff line number Diff line
@@ -300,6 +300,8 @@ struct dma_router { 
 * @chan_id: channel ID for sysfs

 * @dev: class device for sysfs

 * @name: backlink name for sysfs

 * @dbg_client_name: slave name for debugfs in format:

 *	dev_name(requester's dev):channel name, for example: "2b00000.mcasp:tx"

 * @device_node: used to add this to the device chan list

 * @local: per-cpu pointer to a struct dma_chan_percpu

 * @client_count: how many clients are using this channel
@@ -318,6 +320,9 @@ struct dma_chan { 
	int chan_id;

	struct dma_chan_dev *dev;

	const char *name;

#ifdef CONFIG_DEBUG_FS

	char *dbg_client_name;

#endif



	struct list_head device_node;

	struct dma_chan_percpu __percpu *local;
@@ -806,7 +811,9 @@ struct dma_filter { 
 *     called and there are no further references to this structure. This

 *     must be implemented to free resources however many existing drivers

 *     do not and are therefore not safe to unbind while in use.

 *

 * @dbg_summary_show: optional routine to show contents in debugfs; default code

 *     will be used when this is omitted, but custom code can show extra,

 *     controller specific information.

 */

struct dma_device {

	struct kref ref;
@@ -892,6 +899,10 @@ struct dma_device { 
					    struct dma_tx_state *txstate);

	void (*device_issue_pending)(struct dma_chan *chan);

	void (*device_release)(struct dma_device *dev);

	/* debugfs support */

#ifdef CONFIG_DEBUG_FS

	void (*dbg_summary_show)(struct seq_file *s, struct dma_device *dev);

#endif

};



static inline int dmaengine_slave_config(struct dma_chan *chan,

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