Re: [PATCH 1/4] coresight: tmc-etr: Advance buffer pointer in sync buffer.

Leo Yan
2021-04-23T08:25:48Z

On Wed, Apr 21, 2021 at 02:04:10PM +0200, Daniel Kiss wrote:
> With polling the sync could called multiple times in a row. Without this
> change the data will be overwritten at the beginning of the buffer.
>
> Signed-off-by: Daniel Kiss <daniel.kiss@arm.com>
> Signed-off-by: Branislav Rankov <Branislav.Rankov@arm.com>

From the last week, I spent time to dig into AUX trace buffer, thus
this patch set gives me a good chance to apply my learning for perf
ring buffer.

For this patch:

Reviewed-by: Leo Yan <leo.yan@linaro.org>

> ---
> drivers/hwtracing/coresight/coresight-tmc-etr.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> index ea5027e397d02..dd19d1d1c3b38 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> @@ -1442,7 +1442,7 @@ static void tmc_etr_sync_perf_buffer(struct etr_perf_buffer *etr_perf,
> {
> long bytes;
> long pg_idx, pg_offset;
> - unsigned long head = etr_perf->head;
> + unsigned long head;
> char **dst_pages, *src_buf;
> struct etr_buf *etr_buf = etr_perf->etr_buf;
>
> @@ -1465,7 +1465,7 @@ static void tmc_etr_sync_perf_buffer(struct etr_perf_buffer *etr_perf,
> bytes = tmc_etr_buf_get_data(etr_buf, src_offset, to_copy,
> &src_buf);
> if (WARN_ON_ONCE(bytes <= 0))
> - break;
> + return;
> bytes = min(bytes, (long)(PAGE_SIZE - pg_offset));
>
> memcpy(dst_pages[pg_idx] + pg_offset, src_buf, bytes);
> @@ -1483,6 +1483,7 @@ static void tmc_etr_sync_perf_buffer(struct etr_perf_buffer *etr_perf,
> /* Move source pointers */
> src_offset += bytes;
> }
> + etr_perf->head = (pg_idx << PAGE_SHIFT) + pg_offset;
> }
>
> /*
> --
> 2.25.1