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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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