Re: [PATCH] dmaengine: pl330: introduce debugfs interface

[Katsuhiro Suzuki]

Hello Vinod,

Thank you for your comment.
I fix it all and re-post v2 patch.


On 2019/03/16 2:00, Vinod Koul wrote:
> On 15-03-19, 03:49, Katsuhiro Suzuki wrote:
> > This patch adds debugfs interface to show the relationship between
> > DMA threads (hardware resource for transferring data) and DMA
> > channel ID of DMA slave.
> >
> > Typically, PL330 has many slaves than number of DMA threads.
> > So sometimes PL330 cannot allocate DMA threads for all slaves even
> > if an user specify DMA channel ID in devicetree. This interface will
>
> a user :)
>
> > be useful for checking that DMA threads are allocated or not.
> >
> > Below is an output sample:
> >
> > $ sudo cat /sys/kernel/debug/ff1f0000.dmac
> > PL330 physical channels:
> > THREAD:         CHANNEL:
> > --------        -----
> > 0               8
> > 1               9
> > 2               11
> > 3               12
> > 4               14
> > 5               15
> > 6               10
> > 7               --
> >
> > Signed-off-by: Katsuhiro Suzuki <katsuhiro@xxxxxxxxxxxxx>
> > ---
> >   drivers/dma/pl330.c | 51 +++++++++++++++++++++++++++++++++++++++++++++
> >   1 file changed, 51 insertions(+)
> >
> > diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
> > index eec79fdf27a5..aab71863757c 100644
> > --- a/drivers/dma/pl330.c
> > +++ b/drivers/dma/pl330.c
> > @@ -11,6 +11,7 @@
> >    * (at your option) any later version.
> >    */
> >   
> > +#include <linux/debugfs.h>
> >   #include <linux/kernel.h>
> >   #include <linux/io.h>
> >   #include <linux/init.h>
> > @@ -2896,6 +2897,55 @@ static irqreturn_t pl330_irq_handler(int irq, void *data)
> >   	BIT(DMA_SLAVE_BUSWIDTH_4_BYTES) | \
> >   	BIT(DMA_SLAVE_BUSWIDTH_8_BYTES)
> >   
> > +#ifdef CONFIG_DEBUG_FS
> > +static int pl330_debugfs_show(struct seq_file *s, void *data)
> > +{
> > +	struct pl330_dmac *pl330 = s->private;
> > +	int chans, pchs, ch, pr, found;
> > +
> > +	chans = pl330->pcfg.num_chan;
> > +	pchs = pl330->num_peripherals;
> > +
> > +	seq_puts(s, "PL330 physical channels:\n");
> > +	seq_puts(s, "THREAD:\t\tCHANNEL:\n");
> > +	seq_puts(s, "--------\t-----\n");
> > +	for (ch = 0; ch < chans; ch++) {
> > +		struct pl330_thread *thrd = &pl330->channels[ch];
> > +
> > +		found = -1;
>
> found can be uninitialized if we skip this for, which should not be an
> issue as chans> 0!

Exactly. Thanks, 'found' should be changed to for-loop local variable.


> > +		for (pr = 0; pr < pchs; pr++) {
> > +			struct dma_pl330_chan *pch = &pl330->peripherals[pr];
> > +
> > +			if (!pch->thread || thrd->id != pch->thread->id)
> > +				continue;
> > +
> > +			found = pr;
> > +		}
> > +
> > +		seq_printf(s, "%d\t\t", thrd->id);
> > +		if (found == -1)
> > +			seq_puts(s, "--\n");
> > +		else
> > +			seq_printf(s, "%d\n", found);
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +DEFINE_SHOW_ATTRIBUTE(pl330_debugfs);
> > +
> > +static inline void init_pl330_debugfs(struct pl330_dmac *pl330)
> > +{
> > +	debugfs_create_file(dev_name(pl330->ddma.dev),
> > +			    S_IFREG | S_IRUGO, NULL, pl330,
>
> are we not supposed to use octal permissions?
>
> > +			    &pl330_debugfs_fops);
> > +}
> > +#else
> > +static inline void init_pl330_debugfs(struct pl330_dmac *pl330)
> > +{
> > +}
> > +#endif
> > +
> >   /*
> >    * Runtime PM callbacks are provided by amba/bus.c driver.
> >    *
> > @@ -3082,6 +3132,7 @@ pl330_probe(struct amba_device *adev, const struct amba_id *id)
> >   		dev_err(&adev->dev, "unable to set the seg size\n");
> >   
> >   
> > +	init_pl330_debugfs(pl330);
> >   	dev_info(&adev->dev,
> >   		"Loaded driver for PL330 DMAC-%x\n", adev->periphid);
> >   	dev_info(&adev->dev,
> > --
> > 2.20.1

Best Regards,
Katsuhiro Suzuki