1 ===================================================== 2 Freescale i.MX8 DDR Performance Monitoring Unit (PMU) 3 ===================================================== 4 5 There are no performance counters inside the DRAM controller, so performance 6 signals are brought out to the edge of the controller where a set of 4 x 32 bit 7 counters is implemented. This is controlled by the CSV modes programmed in counter 8 control register which causes a large number of PERF signals to be generated. 9 10 Selection of the value for each counter is done via the config registers. There 11 is one register for each counter. Counter 0 is special in that it always counts 12 “time” and when expired causes a lock on itself and the other counters and an 13 interrupt is raised. If any other counter overflows, it continues counting, and 14 no interrupt is raised. 15 16 The "format" directory describes format of the config (event ID) and config1/2 17 (AXI filter setting) fields of the perf_event_attr structure, see /sys/bus/event_source/ 18 devices/imx8_ddr0/format/. The "events" directory describes the events types 19 hardware supported that can be used with perf tool, see /sys/bus/event_source/ 20 devices/imx8_ddr0/events/. The "caps" directory describes filter features implemented 21 in DDR PMU, see /sys/bus/events_source/devices/imx8_ddr0/caps/. 22 23 .. code-block:: bash 24 25 perf stat -a -e imx8_ddr0/cycles/ cmd 26 perf stat -a -e imx8_ddr0/read/,imx8_ddr0/write/ cmd 27 28 AXI filtering is only used by CSV modes 0x41 (axid-read) and 0x42 (axid-write) 29 to count reading or writing matches filter setting. Filter setting is various 30 from different DRAM controller implementations, which is distinguished by quirks 31 in the driver. You also can dump info from userspace, "caps" directory show the 32 type of AXI filter (filter, enhanced_filter and super_filter). Value 0 for 33 un-supported, and value 1 for supported. 34 35 * With DDR_CAP_AXI_ID_FILTER quirk(filter: 1, enhanced_filter: 0, super_filter: 0). 36 Filter is defined with two configuration parts: 37 --AXI_ID defines AxID matching value. 38 --AXI_MASKING defines which bits of AxID are meaningful for the matching. 39 40 - 0: corresponding bit is masked. 41 - 1: corresponding bit is not masked, i.e. used to do the matching. 42 43 AXI_ID and AXI_MASKING are mapped on DPCR1 register in performance counter. 44 When non-masked bits are matching corresponding AXI_ID bits then counter is 45 incremented. Perf counter is incremented if:: 46 47 AxID && AXI_MASKING == AXI_ID && AXI_MASKING 48 49 This filter doesn't support filter different AXI ID for axid-read and axid-write 50 event at the same time as this filter is shared between counters. 51 52 .. code-block:: bash 53 54 perf stat -a -e imx8_ddr0/axid-read,axi_mask=0xMMMM,axi_id=0xDDDD/ cmd 55 perf stat -a -e imx8_ddr0/axid-write,axi_mask=0xMMMM,axi_id=0xDDDD/ cmd 56 57 .. note:: 58 59 axi_mask is inverted in userspace(i.e. set bits are bits to mask), and 60 it will be reverted in driver automatically. so that the user can just specify 61 axi_id to monitor a specific id, rather than having to specify axi_mask. 62 63 .. code-block:: bash 64 65 perf stat -a -e imx8_ddr0/axid-read,axi_id=0x12/ cmd, which will monitor ARID=0x12 66 67 * With DDR_CAP_AXI_ID_FILTER_ENHANCED quirk(filter: 1, enhanced_filter: 1, super_filter: 0). 68 This is an extension to the DDR_CAP_AXI_ID_FILTER quirk which permits 69 counting the number of bytes (as opposed to the number of bursts) from DDR 70 read and write transactions concurrently with another set of data counters. 71 72 * With DDR_CAP_AXI_ID_PORT_CHANNEL_FILTER quirk(filter: 0, enhanced_filter: 0, super_filter: 1). 73 There is a limitation in previous AXI filter, it cannot filter different IDs 74 at the same time as the filter is shared between counters. This quirk is the 75 extension of AXI ID filter. One improvement is that counter 1-3 has their own 76 filter, means that it supports concurrently filter various IDs. Another 77 improvement is that counter 1-3 supports AXI PORT and CHANNEL selection. Support 78 selecting address channel or data channel. 79 80 Filter is defined with 2 configuration registers per counter 1-3. 81 --Counter N MASK COMP register - including AXI_ID and AXI_MASKING. 82 --Counter N MUX CNTL register - including AXI CHANNEL and AXI PORT. 83 84 - 0: address channel 85 - 1: data channel 86 87 PMU in DDR subsystem, only one single port0 exists, so axi_port is reserved 88 which should be 0. 89 90 .. code-block:: bash 91 92 perf stat -a -e imx8_ddr0/axid-read,axi_mask=0xMMMM,axi_id=0xDDDD,axi_channel=0xH/ cmd 93 perf stat -a -e imx8_ddr0/axid-write,axi_mask=0xMMMM,axi_id=0xDDDD,axi_channel=0xH/ cmd 94 95 .. note:: 96 97 axi_channel is inverted in userspace, and it will be reverted in driver 98 automatically. So that users do not need specify axi_channel if want to 99 monitor data channel from DDR transactions, since data channel is more 100 meaningful.
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