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dmaengine: Add basic debugfs support

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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: Peter Ujfalusi <peter.ujfalusi@ti.com>
Link: https://lore.kernel.org/r/20200306142839.17910-2-peter.ujfalusi@ti.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
This commit is contained in:
Peter Ujfalusi 2020-03-06 16:28:37 +02:00 committed by Vinod Koul
parent 05fb806718
commit e937cc1dd7
2 changed files with 87 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

76
drivers/dma/dmaengine.c
View File

@ -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);

13
include/linux/dmaengine.h
View File

@ -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,