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SubjectRe: [PATCH v2 05/10] coresight: trbe: Drop duplicate TRUNCATE flags
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On 7/23/21 6:16 PM, Suzuki K Poulose wrote:
> 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 <anshuman.khandual@arm.com>
> Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
> Cc: Mike Leach <mike.leach@linaro.org>
> Cc: Leo Yan <leo.yan@linaro.org>
> 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);
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