Via the /sys/kernel/debug/dmaengine 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 6 channels:
# cat /sys/kernel/debug/dmaengine
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
dma1chan6: in-use
dma1chan7: 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_show callback to provide
controller specific information instead of the generic one.
It is easy to extend the generic dmaengine_dbg_show() to print additional
information about the used channels.
I have taken the idea from gpiolib.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@xxxxxx>
---
drivers/dma/dmaengine.c | 120 ++++++++++++++++++++++++++++++++++++++
include/linux/dmaengine.h | 12 +++-
2 files changed, 131 insertions(+), 1 deletion(-)
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 75516f9fbab4..7573a4d0f9d7 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -32,6 +32,7 @@
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/platform_device.h>
+#include <linux/debugfs.h>
#include <linux/dma-mapping.h>
#include <linux/init.h>
#include <linux/module.h>
@@ -760,6 +761,13 @@ 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->slave_name = kasprintf(GFP_KERNEL, "%s:%s", dev_name(dev), name);
+ if (!chan->slave_name)
+ dev_warn(dev,
+ "Cannot allocate memory for slave name (debugfs)\n");
+#endif
+
chan->name = kasprintf(GFP_KERNEL, "dma:%s", name);
if (!chan->name) {
dev_warn(dev,
@@ -840,6 +848,13 @@ void dma_release_channel(struct dma_chan *chan)
chan->name = NULL;
chan->slave = NULL;
}
+
+#ifdef CONFIG_DEBUG_FS
+ if (chan->slave_name) {
+ kfree(chan->slave_name);
+ chan->slave_name = NULL;
+ }
+#endif
mutex_unlock(&dma_list_mutex);
}
EXPORT_SYMBOL_GPL(dma_release_channel);
@@ -1562,3 +1577,108 @@ static int __init dma_bus_init(void)
return class_register(&dma_devclass);
}
arch_initcall(dma_bus_init);
+
+#ifdef CONFIG_DEBUG_FS
+static void *dmaengine_seq_start(struct seq_file *s, loff_t *pos)
+{
+ struct dma_device *dma_dev = NULL;
+ loff_t index = *pos;
+
+ s->private = "";
+
+ mutex_lock(&dma_list_mutex);
+ list_for_each_entry(dma_dev, &dma_device_list, global_node)
+ if (index-- == 0) {
+ mutex_unlock(&dma_list_mutex);
+ return dma_dev;
+ }
+ mutex_unlock(&dma_list_mutex);
+
+ return NULL;
+}
+
+static void *dmaengine_seq_next(struct seq_file *s, void *v, loff_t *pos)
+{
+ struct dma_device *dma_dev = v;
+ void *ret = NULL;
+
+ mutex_lock(&dma_list_mutex);
+ if (list_is_last(&dma_dev->global_node, &dma_device_list))
+ ret = NULL;
+ else
+ ret = list_entry(dma_dev->global_node.next,
+ struct dma_device, global_node);
+ mutex_unlock(&dma_list_mutex);
+
+ s->private = "\n";
+ ++*pos;
+
+ return ret;
+}
+
+static void dmaengine_seq_stop(struct seq_file *s, void *v)
+{
+}
+
+static void dmaengine_dbg_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, " dma%dchan%d:", dma_dev->dev_id,
+ chan->chan_id);
+ if (chan->slave_name)
+ seq_printf(s, "\t\t%s\n", chan->slave_name);
+ else
+ seq_printf(s, "\t\t%s\n", "in-use");
+ }
+ }
+}
+
+static int dmaengine_seq_show(struct seq_file *s, void *v)
+{
+ struct dma_device *dma_dev = v;
+
+ seq_printf(s, "%sdma%d (%s): number of channels: %u\n",
+ (char *)s->private, dma_dev->dev_id, dev_name(dma_dev->dev),
+ dma_dev->chancnt);
+
+ if (dma_dev->dbg_show)
+ dma_dev->dbg_show(s, dma_dev);
+ else
+ dmaengine_dbg_show(s, dma_dev);
+
+ return 0;
+}
+
+static const struct seq_operations dmaengine_seq_ops = {
+ .start = dmaengine_seq_start,
+ .next = dmaengine_seq_next,
+ .stop = dmaengine_seq_stop,
+ .show = dmaengine_seq_show,
+};
+
+static int dmaengine_open(struct inode *inode, struct file *file)
+{
+ return seq_open(file, &dmaengine_seq_ops);
+}
+
+static const struct file_operations dmaengine_operations = {
+ .owner = THIS_MODULE,
+ .open = dmaengine_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_release,
+};
+
+static int __init dmaengine_debugfs_init(void)
+{
+ /* /sys/kernel/debug/dmaengine */
+ debugfs_create_file("dmaengine", S_IFREG | 0444, NULL, NULL,
+ &dmaengine_operations);
+ return 0;
+}
+subsys_initcall(dmaengine_debugfs_init);
+
+#endif /* DEBUG_FS */
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 64461fc64e1b..5b9d6b1aa6e9 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -300,6 +300,8 @@ struct dma_router {
* @chan_id: channel ID for sysfs
* @dev: class device for sysfs
* @name: backlink name for sysfs
+ * @slave_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 *slave_name;
+#endif
struct list_head device_node;
struct dma_chan_percpu __percpu *local;
@@ -805,7 +810,9 @@ 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_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;
@@ -891,6 +898,9 @@ struct dma_device {
struct dma_tx_state *txstate);
void (*device_issue_pending)(struct dma_chan *chan);
void (*device_release)(struct dma_device *dev);
+#ifdef CONFIG_DEBUG_FS
+ void (*dbg_show)(struct seq_file *s, struct dma_device *dev);
+#endif
};
static inline int dmaengine_slave_config(struct dma_chan *chan,
--
Peter
Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
