Re: [PATCH 11/19] coresight: trbe: Apply overwrite erratum for only wrap event

[Leo Yan <leo.yan@arm.com>]

On Tue, Dec 02, 2025 at 04:56:47PM +0000, Coresight ML wrote:
> On Tue, Dec 02, 2025 at 12:05:52PM +0000, Suzuki K Poulose wrote:
> > On 01/12/2025 11:22, Leo Yan wrote:
> > > The overwrite erratum occurs only on wrap events, so apply the extra
> > > wrap condition check in the workaround.
> > > 
> > > Signed-off-by: Leo Yan <leo.yan@arm.com>
> > > ---
> > >   drivers/hwtracing/coresight/coresight-trbe.c | 4 ++--
> > >   1 file changed, 2 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c
> > > index e579ea98523c24d23a0cd265dcdd0a46b52b52da..2600af12a8fb94bb8c74efda2a101aacd01b0b34 100644
> > > --- a/drivers/hwtracing/coresight/coresight-trbe.c
> > > +++ b/drivers/hwtracing/coresight/coresight-trbe.c
> > > @@ -714,7 +714,7 @@ static unsigned long trbe_get_trace_size(struct perf_output_handle *handle,
> > >   	 * 64bytes. Thus we ignore the potential triggering of the erratum
> > >   	 * on WRAP and limit the data to LIMIT.
> > >   	 */
> > > -	if (wrap)
> > > +	if (wrap && trbe_may_overwrite_in_fill_mode(buf->cpudata))
> > >   		write = get_trbe_limit_pointer();
> > 
> > This must be trbe_may_write_out_of_range() ?
> 
> SDEN (e.g., [1]) is ambiguous about how the write pointer acts for the
> out-of-range erratum.

Thought again, we should not worry about out-of-range case.

As the workaround always ensures sufficient space beyond the limit, the
write pointer remains valid within the allocated buffer even if it is
updated and crosses that limit.