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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
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13
include/linux/dmaengine.h
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@ -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,