[PATCH v4 1/5] arm64: perf: Basic uncore counter support for Cavium ThunderX SOC

On Thu, Nov 10, 2016 at 04:54:06PM +0000, Mark Rutland wrote:

On Sat, Oct 29, 2016 at 01:55:29PM +0200, Jan Glauber wrote:

quoted

diff --git a/drivers/perf/uncore/uncore_cavium.c b/drivers/perf/uncore/uncore_cavium.c
new file mode 100644
index 0000000..a7b4277
--- /dev/null
+++ b/drivers/perf/uncore/uncore_cavium.c
+ * Some notes about the various counters supported by this "uncore" PMU
+ * and the design:
+ *
+ * All counters are 64 bit long.
+ * There are no overflow interrupts.
+ * Counters are summarized per node/socket.
+ * Most devices appear as separate PCI devices per socket with the exception
+ * of OCX TLK which appears as one PCI device per socket and contains several
+ * units with counters that are merged.

As a general note, as I commented on the QC L2 PMU driver [1,2], we need
to figure out if we should be aggregating physical PMUs or not.

Judging by subsequent patches, each unit has individual counters and
controls, and thus we cannot atomically read/write counters or controls
across them. As such, I do not think we should aggregate them, and
should expose them separately to userspace.

I thought each unit was registered as a separate PMU to perf? Or are you
specifically commenting on the OCX TLK? The comment there suggests that
the units cannot be individually enabled/disabled and, without docs, I
trust that's the case.

Will