On 12/07/18 21:57, Mathieu Poirier wrote:
Hi Suzuki,
On Wed, Jul 11, 2018 at 03:16:39PM +0100, Suzuki K Poulose wrote:
Add support for using TMC-ETR as backend for ETM perf tracing. We use software double buffering at the moment. i.e, the TMC-ETR uses a separate buffer than the perf ring buffer. The data is copied to the perf ring buffer once a session completes.
The TMC-ETR would try to match the larger of perf ring buffer or the ETR buffer size configured via sysfs, scaling down to a minimum limit of 1MB.
Cc: Mathieu Poirier mathieu.poirier@linaro.org Signed-off-by: Suzuki K Poulose suzuki.poulose@arm.com
drivers/hwtracing/coresight/coresight-tmc-etr.c | 265 +++++++++++++++++++++++- drivers/hwtracing/coresight/coresight-tmc.h | 2 + 2 files changed, 265 insertions(+), 2 deletions(-)
+/*
- tmc_etr_sync_perf_buffer: Copy the actual trace data from the hardware
- buffer to the perf ring buffer.
- */
+static void tmc_etr_sync_perf_buffer(struct etr_perf_buffer *etr_perf) +{
- long bytes, to_copy;
- long pg_idx, pg_offset, src_offset;
- unsigned long head = etr_perf->head;
- char **dst_pages, *src_buf;
- struct etr_buf *etr_buf = etr_perf->etr_buf;
- head = PERF_IDX2OFF(etr_perf->head, etr_perf);
I'm puzzled here. Since etr_perf->head is set in tmc_etr_set_perf_buffer() to the value of handle->head, its value is always within the range of the perf ring
IIUC, the handle->head is not necessarily guaranteed to be within the aux-ring buffer.
buffer. In tmc_etr_alloc_perf_buffer() etr_perf->nr_pages is set to the number of pages present in that ring buffer. As such I'm not sure as to why we need the PERF_IDX2OFF() macro.
It seems to me that "head = etr_perf->head;" above is sufficient.
We need to do the step at some point, which could be moved to set_perf_buffer.
- pg_idx = head >> PAGE_SHIFT;
- pg_offset = head & (PAGE_SIZE - 1);
- dst_pages = (char **)etr_perf->pages;
- src_offset = etr_buf->offset;
- to_copy = etr_buf->len;
- while (to_copy > 0) {
/** We can copy minimum of :s/We can copy minimum of :/In one iteration we can copy a minimum of:/
If I'm wrong about the PERF_IDX2OFF(), don't bother respinning just for that.
I have some more fixes for handling the different modes (sysfs vs perf), which I can include in the v2.
Suzuki