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2 Freescale i.MX8 DDR Performance Monitoring Uni 2 Freescale i.MX8 DDR Performance Monitoring Unit (PMU)
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4 4
5 There are no performance counters inside the D 5 There are no performance counters inside the DRAM controller, so performance
6 signals are brought out to the edge of the con 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 7 counters is implemented. This is controlled by the CSV modes programmed in counter
8 control register which causes a large number o 8 control register which causes a large number of PERF signals to be generated.
9 9
10 Selection of the value for each counter is don 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 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 i 12 “time” and when expired causes a lock on itself and the other counters and an
13 interrupt is raised. If any other counter over 13 interrupt is raised. If any other counter overflows, it continues counting, and
14 no interrupt is raised. 14 no interrupt is raised.
15 15
16 The "format" directory describes format of the 16 The "format" directory describes format of the config (event ID) and config1/2
17 (AXI filter setting) fields of the perf_event_ 17 (AXI filter setting) fields of the perf_event_attr structure, see /sys/bus/event_source/
18 devices/imx8_ddr0/format/. The "events" direct 18 devices/imx8_ddr0/format/. The "events" directory describes the events types
19 hardware supported that can be used with perf 19 hardware supported that can be used with perf tool, see /sys/bus/event_source/
20 devices/imx8_ddr0/events/. The "caps" director 20 devices/imx8_ddr0/events/. The "caps" directory describes filter features implemented
21 in DDR PMU, see /sys/bus/events_source/devices 21 in DDR PMU, see /sys/bus/events_source/devices/imx8_ddr0/caps/.
22 22
23 .. code-block:: bash 23 .. code-block:: bash
24 24
25 perf stat -a -e imx8_ddr0/cycles/ cmd 25 perf stat -a -e imx8_ddr0/cycles/ cmd
26 perf stat -a -e imx8_ddr0/read/,imx8_d 26 perf stat -a -e imx8_ddr0/read/,imx8_ddr0/write/ cmd
27 27
28 AXI filtering is only used by CSV modes 0x41 ( 28 AXI filtering is only used by CSV modes 0x41 (axid-read) and 0x42 (axid-write)
29 to count reading or writing matches filter set 29 to count reading or writing matches filter setting. Filter setting is various
30 from different DRAM controller implementations 30 from different DRAM controller implementations, which is distinguished by quirks
31 in the driver. You also can dump info from use 31 in the driver. You also can dump info from userspace, "caps" directory show the
32 type of AXI filter (filter, enhanced_filter an 32 type of AXI filter (filter, enhanced_filter and super_filter). Value 0 for
33 un-supported, and value 1 for supported. 33 un-supported, and value 1 for supported.
34 34
35 * With DDR_CAP_AXI_ID_FILTER quirk(filter: 1, 35 * With DDR_CAP_AXI_ID_FILTER quirk(filter: 1, enhanced_filter: 0, super_filter: 0).
36 Filter is defined with two configuration par 36 Filter is defined with two configuration parts:
37 --AXI_ID defines AxID matching value. 37 --AXI_ID defines AxID matching value.
38 --AXI_MASKING defines which bits of AxID are 38 --AXI_MASKING defines which bits of AxID are meaningful for the matching.
39 39
40 - 0: corresponding bit is masked. 40 - 0: corresponding bit is masked.
41 - 1: corresponding bit is not masked, i. 41 - 1: corresponding bit is not masked, i.e. used to do the matching.
42 42
43 AXI_ID and AXI_MASKING are mapped on DPCR1 r 43 AXI_ID and AXI_MASKING are mapped on DPCR1 register in performance counter.
44 When non-masked bits are matching correspond 44 When non-masked bits are matching corresponding AXI_ID bits then counter is
45 incremented. Perf counter is incremented if: 45 incremented. Perf counter is incremented if::
46 46
47 AxID && AXI_MASKING == AXI_ID && AXI_M 47 AxID && AXI_MASKING == AXI_ID && AXI_MASKING
48 48
49 This filter doesn't support filter different 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 sha 50 event at the same time as this filter is shared between counters.
51 51
52 .. code-block:: bash 52 .. code-block:: bash
53 53
54 perf stat -a -e imx8_ddr0/axid-read,axi_ 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 55 perf stat -a -e imx8_ddr0/axid-write,axi_mask=0xMMMM,axi_id=0xDDDD/ cmd
56 56
57 .. note:: 57 .. note::
58 58
59 axi_mask is inverted in userspace(i.e. s 59 axi_mask is inverted in userspace(i.e. set bits are bits to mask), and
60 it will be reverted in driver automatica 60 it will be reverted in driver automatically. so that the user can just specify
61 axi_id to monitor a specific id, rather 61 axi_id to monitor a specific id, rather than having to specify axi_mask.
62 62
63 .. code-block:: bash 63 .. code-block:: bash
64 64
65 perf stat -a -e imx8_ddr0/axid-read,ax 65 perf stat -a -e imx8_ddr0/axid-read,axi_id=0x12/ cmd, which will monitor ARID=0x12
66 66
67 * With DDR_CAP_AXI_ID_FILTER_ENHANCED quirk(fi 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_F 68 This is an extension to the DDR_CAP_AXI_ID_FILTER quirk which permits
69 counting the number of bytes (as opposed to 69 counting the number of bytes (as opposed to the number of bursts) from DDR
70 read and write transactions concurrently wit 70 read and write transactions concurrently with another set of data counters.
71 71
72 * With DDR_CAP_AXI_ID_PORT_CHANNEL_FILTER quir 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 73 There is a limitation in previous AXI filter, it cannot filter different IDs
74 at the same time as the filter is shared bet 74 at the same time as the filter is shared between counters. This quirk is the
75 extension of AXI ID filter. One improvement 75 extension of AXI ID filter. One improvement is that counter 1-3 has their own
76 filter, means that it supports concurrently 76 filter, means that it supports concurrently filter various IDs. Another
77 improvement is that counter 1-3 supports AXI 77 improvement is that counter 1-3 supports AXI PORT and CHANNEL selection. Support
78 selecting address channel or data channel. 78 selecting address channel or data channel.
79 79
80 Filter is defined with 2 configuration regis 80 Filter is defined with 2 configuration registers per counter 1-3.
81 --Counter N MASK COMP register - including A 81 --Counter N MASK COMP register - including AXI_ID and AXI_MASKING.
82 --Counter N MUX CNTL register - including AX 82 --Counter N MUX CNTL register - including AXI CHANNEL and AXI PORT.
83 83
84 - 0: address channel 84 - 0: address channel
85 - 1: data channel 85 - 1: data channel
86 86
87 PMU in DDR subsystem, only one single port0 87 PMU in DDR subsystem, only one single port0 exists, so axi_port is reserved
88 which should be 0. 88 which should be 0.
89 89
90 .. code-block:: bash 90 .. code-block:: bash
91 91
92 perf stat -a -e imx8_ddr0/axid-read,axi_ 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 93 perf stat -a -e imx8_ddr0/axid-write,axi_mask=0xMMMM,axi_id=0xDDDD,axi_channel=0xH/ cmd
94 94
95 .. note:: 95 .. note::
96 96
97 axi_channel is inverted in userspace, an 97 axi_channel is inverted in userspace, and it will be reverted in driver
98 automatically. So that users do not need 98 automatically. So that users do not need specify axi_channel if want to
99 monitor data channel from DDR transactio 99 monitor data channel from DDR transactions, since data channel is more
100 meaningful. 100 meaningful.
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