mirror of
https://github.com/torvalds/linux.git
synced 2024-12-27 05:11:48 +00:00
0522e130b0
Sphinx is currently outputting a warning where the file 'imx-ddr.rst' is not included in the documentation index. Additionally, the code highlighting and doc formatting can be slightly improved. Signed-off-by: Adam Zerella <adam.zerella@gmail.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
62 lines
2.8 KiB
ReStructuredText
62 lines
2.8 KiB
ReStructuredText
=====================================================
|
|
Freescale i.MX8 DDR Performance Monitoring Unit (PMU)
|
|
=====================================================
|
|
|
|
There are no performance counters inside the DRAM controller, so performance
|
|
signals are brought out to the edge of the controller where a set of 4 x 32 bit
|
|
counters is implemented. This is controlled by the CSV modes programed in counter
|
|
control register which causes a large number of PERF signals to be generated.
|
|
|
|
Selection of the value for each counter is done via the config registers. There
|
|
is one register for each counter. Counter 0 is special in that it always counts
|
|
“time” and when expired causes a lock on itself and the other counters and an
|
|
interrupt is raised. If any other counter overflows, it continues counting, and
|
|
no interrupt is raised.
|
|
|
|
The "format" directory describes format of the config (event ID) and config1
|
|
(AXI filtering) fields of the perf_event_attr structure, see /sys/bus/event_source/
|
|
devices/imx8_ddr0/format/. The "events" directory describes the events types
|
|
hardware supported that can be used with perf tool, see /sys/bus/event_source/
|
|
devices/imx8_ddr0/events/.
|
|
|
|
.. code-block:: bash
|
|
|
|
perf stat -a -e imx8_ddr0/cycles/ cmd
|
|
perf stat -a -e imx8_ddr0/read/,imx8_ddr0/write/ cmd
|
|
|
|
AXI filtering is only used by CSV modes 0x41 (axid-read) and 0x42 (axid-write)
|
|
to count reading or writing matches filter setting. Filter setting is various
|
|
from different DRAM controller implementations, which is distinguished by quirks
|
|
in the driver.
|
|
|
|
* With DDR_CAP_AXI_ID_FILTER quirk.
|
|
Filter is defined with two configuration parts:
|
|
--AXI_ID defines AxID matching value.
|
|
--AXI_MASKING defines which bits of AxID are meaningful for the matching.
|
|
|
|
- 0: corresponding bit is masked.
|
|
- 1: corresponding bit is not masked, i.e. used to do the matching.
|
|
|
|
AXI_ID and AXI_MASKING are mapped on DPCR1 register in performance counter.
|
|
When non-masked bits are matching corresponding AXI_ID bits then counter is
|
|
incremented. Perf counter is incremented if
|
|
AxID && AXI_MASKING == AXI_ID && AXI_MASKING
|
|
|
|
This filter doesn't support filter different AXI ID for axid-read and axid-write
|
|
event at the same time as this filter is shared between counters.
|
|
|
|
.. code-block:: bash
|
|
|
|
perf stat -a -e imx8_ddr0/axid-read,axi_mask=0xMMMM,axi_id=0xDDDD/ cmd
|
|
perf stat -a -e imx8_ddr0/axid-write,axi_mask=0xMMMM,axi_id=0xDDDD/ cmd
|
|
|
|
.. note::
|
|
|
|
axi_mask is inverted in userspace(i.e. set bits are bits to mask), and
|
|
it will be reverted in driver automatically. so that the user can just specify
|
|
axi_id to monitor a specific id, rather than having to specify axi_mask.
|
|
|
|
.. code-block:: bash
|
|
|
|
perf stat -a -e imx8_ddr0/axid-read,axi_id=0x12/ cmd, which will monitor ARID=0x12
|