On 05-02-20, 13:15, Peter Ujfalusi wrote:
> 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>
> ---
> Hi,
>
> Changes since v2:
> - Use dma_chan_name() for printing the channel's name
>
> Changes since v1:
> - Use much more simplified fops for the debugfs file (via DEFINE_SHOW_ATTRIBUTE)
> - do not allow modification to dma_device_list while the debugfs file is read
> - rename the slave_name to dbg_client_name (it is only for debugging)
> - print information about dma_router if it is used by the channel
> - Formating of the output slightly changed
>
> Regards,
> Peter
>
> drivers/dma/dmaengine.c | 65 +++++++++++++++++++++++++++++++++++++++
> include/linux/dmaengine.h | 12 +++++++-
> 2 files changed, 76 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
> index c3b1283b6d31..37c3a4cd5b1a 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 +761,11 @@ 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 +843,11 @@ 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);
> @@ -1562,3 +1573,57 @@ static int __init dma_bus_init(void)
> return class_register(&dma_devclass);
> }
> arch_initcall(dma_bus_init);
> +
> +#ifdef CONFIG_DEBUG_FS
> +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, " %-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_debugfs_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_show)
> + dma_dev->dbg_show(s, dma_dev);
do we really want a custom dbg_show()..? Drivers can add their own
files...
> + else
> + dmaengine_dbg_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_debugfs);
> +
> +static int __init dmaengine_debugfs_init(void)
> +{
> + /* /sys/kernel/debug/dmaengine */
> + debugfs_create_file("dmaengine", 0444, NULL, NULL,
> + &dmaengine_debugfs_fops);
Should we add a directory? That way we can keep adding stuff into that
one
--
~Vinod
