docs/perf: Add explanation for DDR_CAP_AXI_ID_PORT_CHANNEL_FILTER quirk

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/

The "format" directory describes format of the config (event ID) and config1/2

(AXI filter setting) 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/. The "caps" directory describes filter features implemented

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. You also can dump info from userspace, filter in "caps" directory

indicates whether PMU supports AXI ID filter or not; enhanced_filter indicates

whether PMU supports enhanced AXI ID filter or not. Value 0 for un-supported, and

value 1 for supported.

in the driver. You also can dump info from userspace, "caps" directory show the

type of AXI filter (filter, enhanced_filter and super_filter). Value 0 for

un-supported, and value 1 for supported.

* With DDR_CAP_AXI_ID_FILTER quirk(filter: 1, enhanced_filter: 0).

* With DDR_CAP_AXI_ID_FILTER quirk(filter: 1, enhanced_filter: 0, super_filter: 0).

  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.

        perf stat -a -e imx8_ddr0/axid-read,axi_id=0x12/ cmd, which will monitor ARID=0x12

* With DDR_CAP_AXI_ID_FILTER_ENHANCED quirk(filter: 1, enhanced_filter: 1).

* With DDR_CAP_AXI_ID_FILTER_ENHANCED quirk(filter: 1, enhanced_filter: 1, super_filter: 0).

  This is an extension to the DDR_CAP_AXI_ID_FILTER quirk which permits

  counting the number of bytes (as opposed to the number of bursts) from DDR

  read and write transactions concurrently with another set of data counters.

* With DDR_CAP_AXI_ID_PORT_CHANNEL_FILTER quirk(filter: 0, enhanced_filter: 0, super_filter: 1).

  There is a limitation in previous AXI filter, it cannot filter different IDs

  at the same time as the filter is shared between counters. This quirk is the

  extension of AXI ID filter. One improvement is that counter 1-3 has their own

  filter, means that it supports concurrently filter various IDs. Another

  improvement is that counter 1-3 supports AXI PORT and CHANNEL selection. Support

  selecting address channel or data channel.

  Filter is defined with 2 configuration registers per counter 1-3.

  --Counter N MASK COMP register - including AXI_ID and AXI_MASKING.

  --Counter N MUX CNTL register - including AXI CHANNEL and AXI PORT.

      - 0: address channel

      - 1: data channel

  PMU in DDR subsystem, only one single port0 exists, so axi_port is reserved

  which should be 0.

  .. code-block:: bash

      perf stat -a -e imx8_ddr0/axid-read,axi_mask=0xMMMM,axi_id=0xDDDD,axi_channel=0xH/ cmd

      perf stat -a -e imx8_ddr0/axid-write,axi_mask=0xMMMM,axi_id=0xDDDD,axi_channel=0xH/ cmd

  .. note::

      axi_channel is inverted in userspace, and it will be reverted in driver

      automatically. So that users do not need specify axi_channel if want to

      monitor data channel from DDR transactions, since data channel is more

      meaningful.