95 lines
3.4 KiB
ReStructuredText
95 lines
3.4 KiB
ReStructuredText
======================================================================
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Synopsys DesignWare Cores (DWC) PCIe Performance Monitoring Unit (PMU)
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======================================================================
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DesignWare Cores (DWC) PCIe PMU
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===============================
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The PMU is a PCIe configuration space register block provided by each PCIe Root
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Port in a Vendor-Specific Extended Capability named RAS D.E.S (Debug, Error
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injection, and Statistics).
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As the name indicates, the RAS DES capability supports system level
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debugging, AER error injection, and collection of statistics. To facilitate
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collection of statistics, Synopsys DesignWare Cores PCIe controller
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provides the following two features:
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- one 64-bit counter for Time Based Analysis (RX/TX data throughput and
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time spent in each low-power LTSSM state) and
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- one 32-bit counter for Event Counting (error and non-error events for
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a specified lane)
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Note: There is no interrupt for counter overflow.
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Time Based Analysis
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-------------------
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Using this feature you can obtain information regarding RX/TX data
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throughput and time spent in each low-power LTSSM state by the controller.
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The PMU measures data in two categories:
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- Group#0: Percentage of time the controller stays in LTSSM states.
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- Group#1: Amount of data processed (Units of 16 bytes).
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Lane Event counters
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-------------------
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Using this feature you can obtain Error and Non-Error information in
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specific lane by the controller. The PMU event is selected by all of:
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- Group i
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- Event j within the Group i
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- Lane k
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Some of the events only exist for specific configurations.
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DesignWare Cores (DWC) PCIe PMU Driver
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=======================================
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This driver adds PMU devices for each PCIe Root Port named based on the SBDF of
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the Root Port. For example,
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0001:30:03.0 PCI bridge: Device 1ded:8000 (rev 01)
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the PMU device name for this Root Port is dwc_rootport_13018.
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The DWC PCIe PMU driver registers a perf PMU driver, which provides
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description of available events and configuration options in sysfs, see
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/sys/bus/event_source/devices/dwc_rootport_{sbdf}.
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The "format" directory describes format of the config fields of the
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perf_event_attr structure. The "events" directory provides configuration
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templates for all documented events. For example,
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"Rx_PCIe_TLP_Data_Payload" is an equivalent of "eventid=0x22,type=0x1".
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The "perf list" command shall list the available events from sysfs, e.g.::
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$# perf list | grep dwc_rootport
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<...>
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dwc_rootport_13018/Rx_PCIe_TLP_Data_Payload/ [Kernel PMU event]
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<...>
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dwc_rootport_13018/rx_memory_read,lane=?/ [Kernel PMU event]
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Time Based Analysis Event Usage
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-------------------------------
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Example usage of counting PCIe RX TLP data payload (Units of bytes)::
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$# perf stat -a -e dwc_rootport_13018/Rx_PCIe_TLP_Data_Payload/
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The average RX/TX bandwidth can be calculated using the following formula:
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PCIe RX Bandwidth = Rx_PCIe_TLP_Data_Payload / Measure_Time_Window
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PCIe TX Bandwidth = Tx_PCIe_TLP_Data_Payload / Measure_Time_Window
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Lane Event Usage
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-------------------------------
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Each lane has the same event set and to avoid generating a list of hundreds
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of events, the user need to specify the lane ID explicitly, e.g.::
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$# perf stat -a -e dwc_rootport_13018/rx_memory_read,lane=4/
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The driver does not support sampling, therefore "perf record" will not
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work. Per-task (without "-a") perf sessions are not supported.
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