Hi Peter,
On Thu, Jan 30, 2020 at 12:41 PM Peter Ujfalusi <peter.ujfalusi@xxxxxx> 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>
Thanks for your patch!
On Salvator-XS with R-Car H3 ES2.0:
dma0 (ec700000.dma-controller): number of channels: 15
dma1 (ec720000.dma-controller): number of channels: 15
dma2 (e65a0000.dma-controller): number of channels: 2
dma2chan0: e6590000.usb:ch0
dma2chan1: e6590000.usb:ch1
dma3 (e65b0000.dma-controller): number of channels: 2
dma3chan0: e6590000.usb:ch2
dma3chan1: e6590000.usb:ch3
dma4 (e6460000.dma-controller): number of channels: 2
dma4chan0: e659c000.usb:ch0
dma4chan1: e659c000.usb:ch1
dma5 (e6470000.dma-controller): number of channels: 2
dma5chan0: e659c000.usb:ch2
dma5chan1: e659c000.usb:ch3
dma6 (e6700000.dma-controller): number of channels: 15
dma7 (e7300000.dma-controller): number of channels: 15
dma7chan0: e6510000.i2c:tx
dma8 (e7310000.dma-controller): number of channels: 15
dma8chan0: e6550000.serial:tx
dma8chan1: e6550000.serial:rx
> --- a/drivers/dma/dmaengine.c
> +++ b/drivers/dma/dmaengine.c
> @@ -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");
No need to print a message, as the memory allocation core already takes
care of that.
But, do you really need chan->slave_name?
You already have chan->slave and chan->name.
> +#endif
> +
> chan->name = kasprintf(GFP_KERNEL, "dma:%s", name);
> if (!chan->name) {
> dev_warn(dev,
> @@ -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;
Can the dma_device go away after unlocking the list?
Unlike dma_request_chan(), this doesn't increase a refcnt.
> + }
> + 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);
Likewise.
> +
> + 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");
The truncated ternary operator might help here:
seq_printf(s, "\t\t%s\n", chan->slave_name ?: "in-use");
However, you might as well just use dev_name(chan->slave) and chan->name
instead of chan->slave_name.
> + }
> + }
> +}
> +
> +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);
So providing a custom .dbg_show() means replacing the standard info, not
augmenting it?
> + else
> + dmaengine_dbg_show(s, dma_dev);
> +
> + return 0;
> +}
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
