Re: [PATCH v2 18/27] coresight: catu: Add support for scatter gather tables

[Suzuki K Poulose]

On 07/05/18 21:25, Mathieu Poirier wrote:
> On Tue, May 01, 2018 at 10:10:48AM +0100, Suzuki K Poulose wrote:
> > This patch adds the support for setting up a SG table for use
> > by the CATU. We reuse the tmc_sg_table to represent the table/data
> > pages, even though the table format is different.

...

> > diff --git a/drivers/hwtracing/coresight/coresight-catu.c b/drivers/hwtracing/coresight/coresight-catu.c
> > index 2cd69a6..4cc2928 100644
> > --- a/drivers/hwtracing/coresight/coresight-catu.c
> > +++ b/drivers/hwtracing/coresight/coresight-catu.c
> > @@ -16,10 +16,419 @@

...

> > +
> > +/*
> > + * Update the valid bit for a given range of indices [start, end)
> > + * in the given table @table.
> > + */
> > +static inline void catu_update_state_range(cate_t *table, int start,
> > +						 int end, int valid)
>
> Indentation

...

> > +#ifdef CATU_DEBUG
> > +static void catu_dump_table(struct tmc_sg_table *catu_table)
> > +{
> > +	int i;
> > +	cate_t *table;
> > +	unsigned long table_end, buf_size, offset = 0;
> > +
> > +	buf_size = tmc_sg_table_buf_size(catu_table);
> > +	dev_dbg(catu_table->dev,
> > +		"Dump table %p, tdaddr: %llx\n",
> > +		catu_table, catu_table->table_daddr);
> > +
> > +	while (offset < buf_size) {
> > +		table_end = offset + SZ_1M < buf_size ?
> > +			    offset + SZ_1M : buf_size;
> > +		table = catu_get_table(catu_table, offset, NULL);
> > +		for (i = 0; offset < table_end; i++, offset += CATU_PAGE_SIZE)
> > +			dev_dbg(catu_table->dev, "%d: %llx\n", i, table[i]);
> > +		dev_dbg(catu_table->dev, "Prev : %llx, Next: %llx\n",
> > +			table[CATU_LINK_PREV], table[CATU_LINK_NEXT]);
> > +		dev_dbg(catu_table->dev, "== End of sub-table ===");
> > +	}
> > +	dev_dbg(catu_table->dev, "== End of Table ===");
> > +}
> > +
> > +#else
> > +static inline void catu_dump_table(struct tmc_sg_table *catu_table)
> > +{
> > +}
> > +#endif
>
> I think this approach is better than peppering the code with #ifdefs as it was
> done for ETR.  Please fix that to replicate what you've done here.

OK

> > +
> > +/*
> > + * catu_populate_table : Populate the given CATU table.
> > + * The table is always populated as a circular table.
> > + * i.e, the "prev" link of the "first" table points to the "last"
> > + * table and the "next" link of the "last" table points to the
> > + * "first" table. The buffer should be made linear by calling
> > + * catu_set_table().
> > + */
> > +static void
> > +catu_populate_table(struct tmc_sg_table *catu_table)
> > +{

...

> > +	while (offset < buf_size) {
> > +		/*
> > +		 * The @offset is always 1M aligned here and we have an
> > +		 * empty table @table_ptr to fill. Each table can address
> > +		 * upto 1MB data buffer. The last table may have fewer
> > +		 * entries if the buffer size is not aligned.
> > +		 */
> > +		last_offset = (offset + SZ_1M) < buf_size ?
> > +			      (offset + SZ_1M) : buf_size;
> > +		for (i = 0; offset < last_offset; i++) {
> > +
> > +			data_daddr = catu_table->data_pages.daddrs[dpidx] +
> > +				     s_dpidx * CATU_PAGE_SIZE;
> > +#ifdef CATU_DEBUG
> > +			dev_dbg(catu_table->dev,
> > +				"[table %5d:%03d] 0x%llx\n",
> > +				(offset >> 20), i, data_daddr);
> > +#endif
>
> I'm not a fan of adding #ifdefs in the code like this.  I think it is better to
> have a wrapper (that resolves to nothing if CATU_DEBUG is not defined) and
> handle the output in there.


> > +
> > +	catu_populate_table(catu_table);
> > +	/* Make the buf linear from offset 0 */
> > +	(void)catu_set_table(catu_table, 0, size);
> > +
> > +	dev_dbg(catu_dev,
> > +		"Setup table %p, size %ldKB, %d table pages\n",
> > +		catu_table, (unsigned long)size >> 10,  nr_tpages);
>
> I think this should also be wrapped in a special output debug function.

I could do something like :

#ifdef CATU_DEBUG
#define catu_dbg(fmt, ...)	dev_dbg(fmt, __VA_ARGS__)
#else
#define catu_dbg(fmt, ...)	do { } while (0)
#endif

And use catu_dbg() for the sprinkled prints.

Cheers
Suzuki