Re: [PATCH v2 05/10] coresight: trbe: Drop duplicate TRUNCATE flags

On 7/23/21 6:16 PM, Suzuki K Poulose wrote:

quoted

We mark the buffer as TRUNCATED when there is no space left
in the buffer. But we do it at different points.
     __trbe_normal_offset()
and also, at all the callers of the above function via
compute_trbe_buffer_limit(), when the limit == base (i.e
offset = 0 as returned by the __trbe_normal_offset()).

So, given that the callers already mark the buffer as TRUNCATED
drop the caller inside the __trbe_normal_offset().

This is in preparation to moving the handling of TRUNCATED
into a central place.

Cc: Anshuman Khandual <redacted>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Leach <redacted>
Cc: Leo Yan <redacted>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
  drivers/hwtracing/coresight/coresight-trbe.c | 7 +------
  1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c
index 446f080f8320..62e1a08f73ff 100644
--- a/drivers/hwtracing/coresight/coresight-trbe.c
+++ b/drivers/hwtracing/coresight/coresight-trbe.c

@@ -253,13 +253,9 @@ static unsigned long __trbe_normal_offset(struct perf_output_handle *handle)
  	 * trbe_base				trbe_base + nr_pages
  	 *
  	 * Perf aux buffer does not have any space for the driver to write into.
-	 * Just communicate trace truncation event to the user space by marking
-	 * it with PERF_AUX_FLAG_TRUNCATED.
  	 */
-	if (!handle->size) {
-		perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
+	if (!handle->size)
  		return 0;
-	}
  
  	/* Compute the tail and wakeup indices now that we've aligned head */
  	tail = PERF_IDX2OFF(handle->head + handle->size, buf);

@@ -361,7 +357,6 @@ static unsigned long __trbe_normal_offset(struct perf_output_handle *handle)
  		return limit;
  
  	trbe_pad_buf(handle, handle->size);
-	perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
  	return 0;
  }

What about in trbe_handle_spurious() path which used to set the flag via
compute_trbe_buffer_limit(), but would not any more after this change. I
guess following additional change would be required to preserve the past
behaviour.

--- a/drivers/hwtracing/coresight/coresight-trbe.c
+++ b/drivers/hwtracing/coresight/coresight-trbe.c

@@ -685,6 +685,7 @@ static void trbe_handle_spurious(struct perf_output_handle *handle)
         buf->trbe_write = buf->trbe_base + PERF_IDX2OFF(handle->head, buf);
         if (buf->trbe_limit == buf->trbe_base) {
                 trbe_drain_and_disable_local();
+               perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
                 return;
         }
         trbe_enable_hw(buf);