docs/perf: Add explanation for DDR_CAP_AXI_ID_PORT_CHANNEL_FILTER quirk

Add explanation for DDR_CAP_AXI_ID_PORT_CHANNEL_FILTER quirk.

Signed-off-by: Xu Yang <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Will Deacon <[e-mail]>

Documentation/admin-guide/perf/imx-ddr.rst

···
 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.