docs/perf: Add documentation for the Amlogic G12 DDR PMU

Add a user guide to show how to use DDR PMU to
monitor DDR bandwidth on Amlogic G12 SoC

Signed-off-by: Jiucheng Xu <jiucheng.xu@amlogic.com>
Reviewed-by: Chris Healy <healych@amazon.com>
Link: https://lore.kernel.org/r/20221121021602.3306998-2-jiucheng.xu@amlogic.com
Signed-off-by: Will Deacon <will@kernel.org>

Documentation/admin-guide/perf/index.rst

@@ -20,3 +20,4 @@ Performance monitor support
    thunderx2-pmu
    alibaba_pmu
    nvidia-pmu
+   meson-ddr-pmu

Documentation/admin-guide/perf/meson-ddr-pmu.rst

@@ -0,0 +1,70 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===========================================================
+Amlogic SoC DDR Bandwidth Performance Monitoring Unit (PMU)
+===========================================================
+
+The Amlogic Meson G12 SoC contains a bandwidth monitor inside DRAM controller.
+The monitor includes 4 channels. Each channel can count the request accessing
+DRAM. The channel can count up to 3 AXI port simultaneously. It can be helpful
+to show if the performance bottleneck is on DDR bandwidth.
+
+Currently, this driver supports the following 5 perf events:
+
++ meson_ddr_bw/total_rw_bytes/
++ meson_ddr_bw/chan_1_rw_bytes/
++ meson_ddr_bw/chan_2_rw_bytes/
++ meson_ddr_bw/chan_3_rw_bytes/
++ meson_ddr_bw/chan_4_rw_bytes/
+
+meson_ddr_bw/chan_{1,2,3,4}_rw_bytes/ events are channel-specific events.
+Each channel support filtering, which can let the channel to monitor
+individual IP module in SoC.
+
+Below are DDR access request event filter keywords:
+
++ arm             - from CPU
++ vpu_read1       - from OSD + VPP read
++ gpu             - from 3D GPU
++ pcie            - from PCIe controller
++ hdcp            - from HDCP controller
++ hevc_front      - from HEVC codec front end
++ usb3_0          - from USB3.0 controller
++ hevc_back       - from HEVC codec back end
++ h265enc         - from HEVC encoder
++ vpu_read2       - from DI read
++ vpu_write1      - from VDIN write
++ vpu_write2      - from di write
++ vdec            - from legacy codec video decoder
++ hcodec          - from H264 encoder
++ ge2d            - from ge2d
++ spicc1          - from SPI controller 1
++ usb0            - from USB2.0 controller 0
++ dma             - from system DMA controller 1
++ arb0            - from arb0
++ sd_emmc_b       - from SD eMMC b controller
++ usb1            - from USB2.0 controller 1
++ audio           - from Audio module
++ sd_emmc_c       - from SD eMMC c controller
++ spicc2          - from SPI controller 2
++ ethernet        - from Ethernet controller
+
+
+Examples:
+
+  + Show the total DDR bandwidth per seconds:
+
+    .. code-block:: bash
+
+       perf stat -a -e meson_ddr_bw/total_rw_bytes/ -I 1000 sleep 10
+
+
+  + Show individual DDR bandwidth from CPU and GPU respectively, as well as
+    sum of them:
+
+    .. code-block:: bash
+
+       perf stat -a -e meson_ddr_bw/chan_1_rw_bytes,arm=1/ -I 1000 sleep 10
+       perf stat -a -e meson_ddr_bw/chan_2_rw_bytes,gpu=1/ -I 1000 sleep 10
+       perf stat -a -e meson_ddr_bw/chan_3_rw_bytes,arm=1,gpu=1/ -I 1000 sleep 10
+

MAINTAINERS

@@ -1098,6 +1098,7 @@ M:	Jiucheng Xu <jiucheng.xu@amlogic.com>
 L:	linux-amlogic@lists.infradead.org
 S:	Supported
 W:	http://www.amlogic.com
+F:	Documentation/admin-guide/perf/meson-ddr-pmu.rst
 F:	drivers/perf/amlogic/
 F:	include/soc/amlogic/