Re: [PATCH 06/17] coresight: tmc: Make ETR SG table circular

[Suzuki K Poulose]

On 01/11/17 23:47, Mathieu Poirier wrote:
> On Thu, Oct 19, 2017 at 06:15:42PM +0100, Suzuki K Poulose wrote:
> > Make the ETR SG table Circular buffer so that we could start
> > at any of the SG pages and use the entire buffer for tracing.
> > This can be achieved by :
> >
> > 1) Keeping an additional LINK pointer at the very end of the
> > SG table, i.e, after the LAST buffer entry, to point back to
> > the beginning of the first table. This will allow us to use
> > the buffer normally when we start the trace at offset 0 of
> > the buffer, as the LAST buffer entry hints the TMC-ETR and
> > it automatically wraps to the offset 0.
> >
> > 2) If we want to start at any other ETR SG page aligned offset,
> > we could :
> >   a) Make the preceding page entry as LAST entry.
> >   b) Make the original LAST entry a normal entry.
> >   c) Use the table pointer to the "new" start offset as the
> >      base of the table address.
> > This works as the TMC doesn't mandate that the page table
> > base address should be 4K page aligned.
> >
> > Cc: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
> > Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> > ---

> > +static int __maybe_unused
> > +tmc_etr_sg_table_rotate(struct etr_sg_table *etr_table, u64 base_offset)
> > +{
> > +	u32 last_entry, first_entry;
> > +	u64 last_offset;
> > +	struct tmc_sg_table *sg_table = etr_table->sg_table;
> > +	sgte_t *table_ptr = sg_table->table_vaddr;
> > +	ssize_t buf_size = tmc_sg_table_buf_size(sg_table);
> > +
> > +	/* Offset should always be SG PAGE_SIZE aligned */
> > +	if (base_offset & (ETR_SG_PAGE_SIZE - 1)) {
> > +		pr_debug("unaligned base offset %llx\n", base_offset);
> > +		return -EINVAL;
> > +	}
> > +	/* Make sure the offset is within the range */
> > +	if (base_offset < 0 || base_offset > buf_size) {
> > +		base_offset = (base_offset + buf_size) % buf_size;
> > +		pr_debug("Resetting offset to %llx\n", base_offset);
> > +	}
> > +	first_entry = tmc_etr_sg_offset_to_table_index(base_offset);
> > +	if (first_entry == etr_table->first_entry) {
> > +		pr_debug("Head is already at %llx, skipping\n", base_offset);
> > +		return 0;
> > +	}
> > +
> > +	/* Last entry should be the previous one to the new "base" */
> > +	last_offset = ((base_offset - ETR_SG_PAGE_SIZE) + buf_size) % buf_size;
> > +	last_entry = tmc_etr_sg_offset_to_table_index(last_offset);
> > +
> > +	/* Reset the current Last page to Normal and new Last page to NORMAL */
> > +	tmc_etr_sg_update_type(&table_ptr[etr_table->last_entry],
> > +				 ETR_SG_ET_NORMAL);
> > +	tmc_etr_sg_update_type(&table_ptr[last_entry], ETR_SG_ET_LAST);
> > +	etr_table->hwaddr = tmc_etr_sg_table_index_to_daddr(sg_table,
> > +							    first_entry);
> > +	etr_table->first_entry = first_entry;
> > +	etr_table->last_entry = last_entry;
> > +	pr_debug("table rotated to offset %llx-%llx, entries (%d - %d), dba: %llx\n",
> > +			base_offset, last_offset, first_entry, last_entry,
> > +			etr_table->hwaddr);
>
> The above line generates a warning when compiling for ARMv7.

Where you running with LPAE off ? That could probably be the case,
where hwaddr could be 32bit or 64bit depending on whether LPAE
is enabled. I will fix it.

I have fixed some other warnings with ARMv7 with LPAE.

Suzuki