MPSoC的DDR控制器的數據通道上集成了 AXI performance monitors (APM)。具體情況，可以參考Xilinx UG1085 (v2.2)中Chapter 15的“Figure 15‐1: PS Interconnect”或者Figure 17-1。

1. APM驅動程序
對于AXI performance monitors (APM)，xilinx提供的驅動程序是drivers\uio\uio_xilinx_apm.c，相關匹配字符串和主要數據結構如下：

static const struct of_device_id xapm_of_match[] = {
        { .compatible = "xlnx,axi-perf-monitor", },
        { /* end of table*/ }
};

MODULE_DEVICE_TABLE(of, xapm_of_match);
static struct platform_driver xapm_driver = {
        .driver = {
                 .name = "xilinx-axipmon",
                 .of_match_table = xapm_of_match,
                 .pm = &xapm_dev_pm_ops,
        },
        .probe = xapm_probe,
        .remove = xapm_remove,
};

APM驅動程序最終會注冊UIO設備。

在每個單板的device tree里，會支持DDR的APM。比如，在VCU TRD里，為DDR的APM定義了下面字段。

 perf-monitor@fd0b0000 {
                    compatible = "xlnx,axi-perf-monitor";
                    reg = <0x00 0xfd0b0000 0x00 0x10000> ;
                    interrupts = <0x00 0x7b 0x04> ;
                    interrupt-parent = <0x04> ;
                    xlnx,enable-profile = <0x00> ;
                    xlnx,enable-trace = <0x00> ;
                    xlnx,num-monitor-slots = <0x06> ;
                    xlnx,enable-event-count = <0x01> ;
                    xlnx,enable-event-log = <0x00> ;
                    xlnx,have-sampled-metric-cnt = <0x01> ;
                    xlnx,num-of-counters = <0x0a> ;
                    xlnx,metric-count-width = <0x20> ;
                    xlnx,metrics-sample-count-width = <0x20> ;
                    xlnx,global-count-width = <0x20> ;
                    xlnx,metric-count-scale = <0x01> ;
                    clocks = <0x03 0x1c> ;
                    phandle = <0x9b> ;
         };

     perf_monitor_ddr = "/amba/perf-monitor@fd0b0000";

OCM、CCI等模塊也有APM。

perf_monitor_ocm = "/amba/perf-monitor@ffa00000";
     perf_monitor_cci = "/amba/perf-monitor@fd490000";
     perf_monitor_lpd = "/amba/perf-monitor@ffa10000";

單板Linux啟動后，能查詢到對應的UIO設備。

root@vcu_trd:~# ls /dev/uio*
/dev/uio0  /dev/uio1  /dev/uio2  /dev/uio3  /dev/uio4

2. APM用戶態程序
對于AXI performance monitors (APM)，xilinx也提供了用戶態程序,是apm_main.elf。使用apm_main.elf，可以查詢APM監視到的DDR帶寬利用情況。

root@vcu_trd:~# chmod +x apm_main.elf
root@vcu_trd:~# ./apm_main.elf -d /dev/uio0
AXI PMON is in Advanced Mode
port 1 read: 0 0.00 MBps
port 1 write: 0 0.00 MBps
port 2 read: 0 0.00 MBps
port 2 write: 0 0.00 MBps
port 4 read: 0 0.00 MBps
port 4 write: 0 0.00 MBps
port 5 read: 0 0.00 MBps
port 5 write: 0 0.00 MBps
root@vcu_trd:~#
root@vcu_trd:~# ./apm_main.elf -d /dev/uio1
AXI PMON is in Advanced Mode
port 1 read: 12523440 12.52 MBps
port 1 write: 7564856 7.56 MBps
port 2 read: 13290992 13.29 MBps
port 2 write: 7493209 7.49 MBps
port 4 read: 0 0.00 MBps
port 4 write: 331253760 331.25 MBps
port 5 read: 667254864 667.25 MBps
port 5 write: 320656878 320.66 MBps
root@vcu_trd:~# ./apm_main.elf -d /dev/uio2
AXI PMON is in Advanced Mode
port 1 read: 0 0.00 MBps
port 1 write: 0 0.00 MBps
port 2 read: 0 0.00 MBps
port 2 write: 0 0.00 MBps
port 4 read: 0 0.00 MBps
port 4 write: 0 0.00 MBps
port 5 read: 0 0.00 MBps
port 5 write: 0 0.00 MBps
root@vcu_trd:~# ./apm_main.elf -d /dev/uio3
AXI PMON is in Advanced Mode
port 1 read: 0 0.00 MBps
port 1 write: 0 0.00 MBps
port 2 read: 0 0.00 MBps
port 2 write: 0 0.00 MBps
port 4 read: 0 0.00 MBps
port 4 write: 0 0.00 MBps
port 5 read: 0 0.00 MBps
port 5 write: 0 0.00 MBps

上述設備“/dev/uio1”代表DDR APM1。在使用VCU TRD進行1080p編碼時，port 4寫帶寬331.25 MBps，port 5讀帶寬667.25 MBps，port 5寫帶寬320.66 MBps。每個DDR port對應的硬件模塊，請參考ug1085的Figure 17-1。port 4連接到了HP 1/HP 2。port 5連接到了HP 3。

審核編輯：湯梓紅