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.poir...@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poul...@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
