0001 What: /sys/bus/coresight/devices/etm<N>/enable_source
0002 Date: April 2015
0003 KernelVersion: 4.01
0004 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0005 Description: (RW) Enable/disable tracing on this specific trace entiry.
0006 Enabling a source implies the source has been configured
0007 properly and a sink has been identidifed for it. The path
0008 of coresight components linking the source to the sink is
0009 configured and managed automatically by the coresight framework.
0010
0011 What: /sys/bus/coresight/devices/etm<N>/cpu
0012 Date: April 2015
0013 KernelVersion: 4.01
0014 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0015 Description: (Read) The CPU this tracing entity is associated with.
0016
0017 What: /sys/bus/coresight/devices/etm<N>/nr_pe_cmp
0018 Date: April 2015
0019 KernelVersion: 4.01
0020 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0021 Description: (Read) Indicates the number of PE comparator inputs that are
0022 available for tracing.
0023
0024 What: /sys/bus/coresight/devices/etm<N>/nr_addr_cmp
0025 Date: April 2015
0026 KernelVersion: 4.01
0027 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0028 Description: (Read) Indicates the number of address comparator pairs that are
0029 available for tracing.
0030
0031 What: /sys/bus/coresight/devices/etm<N>/nr_cntr
0032 Date: April 2015
0033 KernelVersion: 4.01
0034 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0035 Description: (Read) Indicates the number of counters that are available for
0036 tracing.
0037
0038 What: /sys/bus/coresight/devices/etm<N>/nr_ext_inp
0039 Date: April 2015
0040 KernelVersion: 4.01
0041 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0042 Description: (Read) Indicates how many external inputs are implemented.
0043
0044 What: /sys/bus/coresight/devices/etm<N>/numcidc
0045 Date: April 2015
0046 KernelVersion: 4.01
0047 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0048 Description: (Read) Indicates the number of Context ID comparators that are
0049 available for tracing.
0050
0051 What: /sys/bus/coresight/devices/etm<N>/numvmidc
0052 Date: April 2015
0053 KernelVersion: 4.01
0054 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0055 Description: (Read) Indicates the number of VMID comparators that are available
0056 for tracing.
0057
0058 What: /sys/bus/coresight/devices/etm<N>/nrseqstate
0059 Date: April 2015
0060 KernelVersion: 4.01
0061 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0062 Description: (Read) Indicates the number of sequencer states that are
0063 implemented.
0064
0065 What: /sys/bus/coresight/devices/etm<N>/nr_resource
0066 Date: April 2015
0067 KernelVersion: 4.01
0068 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0069 Description: (Read) Indicates the number of resource selection pairs that are
0070 available for tracing.
0071
0072 What: /sys/bus/coresight/devices/etm<N>/nr_ss_cmp
0073 Date: April 2015
0074 KernelVersion: 4.01
0075 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0076 Description: (Read) Indicates the number of single-shot comparator controls that
0077 are available for tracing.
0078
0079 What: /sys/bus/coresight/devices/etm<N>/reset
0080 Date: April 2015
0081 KernelVersion: 4.01
0082 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0083 Description: (Write) Cancels all configuration on a trace unit and set it back
0084 to its boot configuration.
0085
0086 What: /sys/bus/coresight/devices/etm<N>/mode
0087 Date: April 2015
0088 KernelVersion: 4.01
0089 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0090 Description: (RW) Controls various modes supported by this ETM, for example
0091 P0 instruction tracing, branch broadcast, cycle counting and
0092 context ID tracing.
0093
0094 What: /sys/bus/coresight/devices/etm<N>/pe
0095 Date: April 2015
0096 KernelVersion: 4.01
0097 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0098 Description: (RW) Controls which PE to trace.
0099
0100 What: /sys/bus/coresight/devices/etm<N>/event
0101 Date: April 2015
0102 KernelVersion: 4.01
0103 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0104 Description: (RW) Controls the tracing of arbitrary events from bank 0 to 3.
0105
0106 What: /sys/bus/coresight/devices/etm<N>/event_instren
0107 Date: April 2015
0108 KernelVersion: 4.01
0109 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0110 Description: (RW) Controls the behavior of the events in bank 0 to 3.
0111
0112 What: /sys/bus/coresight/devices/etm<N>/event_ts
0113 Date: April 2015
0114 KernelVersion: 4.01
0115 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0116 Description: (RW) Controls the insertion of global timestamps in the trace
0117 streams.
0118
0119 What: /sys/bus/coresight/devices/etm<N>/syncfreq
0120 Date: April 2015
0121 KernelVersion: 4.01
0122 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0123 Description: (RW) Controls how often trace synchronization requests occur.
0124
0125 What: /sys/bus/coresight/devices/etm<N>/cyc_threshold
0126 Date: April 2015
0127 KernelVersion: 4.01
0128 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0129 Description: (RW) Sets the threshold value for cycle counting.
0130
0131 What: /sys/bus/coresight/devices/etm<N>/bb_ctrl
0132 Date: April 2015
0133 KernelVersion: 4.01
0134 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0135 Description: (RW) Controls which regions in the memory map are enabled to
0136 use branch broadcasting.
0137
0138 What: /sys/bus/coresight/devices/etm<N>/event_vinst
0139 Date: April 2015
0140 KernelVersion: 4.01
0141 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0142 Description: (RW) Controls instruction trace filtering.
0143
0144 What: /sys/bus/coresight/devices/etm<N>/s_exlevel_vinst
0145 Date: April 2015
0146 KernelVersion: 4.01
0147 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0148 Description: (RW) In Secure state, each bit controls whether instruction
0149 tracing is enabled for the corresponding exception level.
0150
0151 What: /sys/bus/coresight/devices/etm<N>/ns_exlevel_vinst
0152 Date: April 2015
0153 KernelVersion: 4.01
0154 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0155 Description: (RW) In non-secure state, each bit controls whether instruction
0156 tracing is enabled for the corresponding exception level.
0157
0158 What: /sys/bus/coresight/devices/etm<N>/addr_idx
0159 Date: April 2015
0160 KernelVersion: 4.01
0161 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0162 Description: (RW) Select which address comparator or pair (of comparators) to
0163 work with.
0164
0165 What: /sys/bus/coresight/devices/etm<N>/addr_instdatatype
0166 Date: April 2015
0167 KernelVersion: 4.01
0168 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0169 Description: (RW) Controls what type of comparison the trace unit performs.
0170
0171 What: /sys/bus/coresight/devices/etm<N>/addr_single
0172 Date: April 2015
0173 KernelVersion: 4.01
0174 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0175 Description: (RW) Used to setup single address comparator values.
0176
0177 What: /sys/bus/coresight/devices/etm<N>/addr_range
0178 Date: April 2015
0179 KernelVersion: 4.01
0180 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0181 Description: (RW) Used to setup address range comparator values.
0182
0183 What: /sys/bus/coresight/devices/etm<N>/seq_idx
0184 Date: April 2015
0185 KernelVersion: 4.01
0186 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0187 Description: (RW) Select which sequensor.
0188
0189 What: /sys/bus/coresight/devices/etm<N>/seq_state
0190 Date: April 2015
0191 KernelVersion: 4.01
0192 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0193 Description: (RW) Use this to set, or read, the sequencer state.
0194
0195 What: /sys/bus/coresight/devices/etm<N>/seq_event
0196 Date: April 2015
0197 KernelVersion: 4.01
0198 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0199 Description: (RW) Moves the sequencer state to a specific state.
0200
0201 What: /sys/bus/coresight/devices/etm<N>/seq_reset_event
0202 Date: April 2015
0203 KernelVersion: 4.01
0204 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0205 Description: (RW) Moves the sequencer to state 0 when a programmed event
0206 occurs.
0207
0208 What: /sys/bus/coresight/devices/etm<N>/cntr_idx
0209 Date: April 2015
0210 KernelVersion: 4.01
0211 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0212 Description: (RW) Select which counter unit to work with.
0213
0214 What: /sys/bus/coresight/devices/etm<N>/cntrldvr
0215 Date: April 2015
0216 KernelVersion: 4.01
0217 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0218 Description: (RW) This sets or returns the reload count value of the
0219 specific counter.
0220
0221 What: /sys/bus/coresight/devices/etm<N>/cntr_val
0222 Date: April 2015
0223 KernelVersion: 4.01
0224 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0225 Description: (RW) This sets or returns the current count value of the
0226 specific counter.
0227
0228 What: /sys/bus/coresight/devices/etm<N>/cntr_ctrl
0229 Date: April 2015
0230 KernelVersion: 4.01
0231 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0232 Description: (RW) Controls the operation of the selected counter.
0233
0234 What: /sys/bus/coresight/devices/etm<N>/res_idx
0235 Date: April 2015
0236 KernelVersion: 4.01
0237 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0238 Description: (RW) Select which resource selection unit to work with.
0239
0240 What: /sys/bus/coresight/devices/etm<N>/res_ctrl
0241 Date: April 2015
0242 KernelVersion: 4.01
0243 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0244 Description: (RW) Controls the selection of the resources in the trace unit.
0245
0246 What: /sys/bus/coresight/devices/etm<N>/ctxid_idx
0247 Date: April 2015
0248 KernelVersion: 4.01
0249 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0250 Description: (RW) Select which context ID comparator to work with.
0251
0252 What: /sys/bus/coresight/devices/etm<N>/ctxid_pid
0253 Date: April 2015
0254 KernelVersion: 4.01
0255 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0256 Description: (RW) Get/Set the context ID comparator value to trigger on.
0257
0258 What: /sys/bus/coresight/devices/etm<N>/ctxid_masks
0259 Date: April 2015
0260 KernelVersion: 4.01
0261 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0262 Description: (RW) Mask for all 8 context ID comparator value
0263 registers (if implemented).
0264
0265 What: /sys/bus/coresight/devices/etm<N>/vmid_idx
0266 Date: April 2015
0267 KernelVersion: 4.01
0268 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0269 Description: (RW) Select which virtual machine ID comparator to work with.
0270
0271 What: /sys/bus/coresight/devices/etm<N>/vmid_val
0272 Date: April 2015
0273 KernelVersion: 4.01
0274 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0275 Description: (RW) Get/Set the virtual machine ID comparator value to
0276 trigger on.
0277
0278 What: /sys/bus/coresight/devices/etm<N>/vmid_masks
0279 Date: April 2015
0280 KernelVersion: 4.01
0281 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0282 Description: (RW) Mask for all 8 virtual machine ID comparator value
0283 registers (if implemented).
0284
0285 What: /sys/bus/coresight/devices/etm<N>/addr_exlevel_s_ns
0286 Date: December 2019
0287 KernelVersion: 5.5
0288 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0289 Description: (RW) Set the Exception Level matching bits for secure and
0290 non-secure exception levels.
0291
0292 What: /sys/bus/coresight/devices/etm<N>/vinst_pe_cmp_start_stop
0293 Date: December 2019
0294 KernelVersion: 5.5
0295 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0296 Description: (RW) Access the start stop control register for PE input
0297 comparators.
0298
0299 What: /sys/bus/coresight/devices/etm<N>/addr_cmp_view
0300 Date: December 2019
0301 KernelVersion: 5.5
0302 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0303 Description: (Read) Print the current settings for the selected address
0304 comparator.
0305
0306 What: /sys/bus/coresight/devices/etm<N>/sshot_idx
0307 Date: December 2019
0308 KernelVersion: 5.5
0309 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0310 Description: (RW) Select the single shot control register to access.
0311
0312 What: /sys/bus/coresight/devices/etm<N>/sshot_ctrl
0313 Date: December 2019
0314 KernelVersion: 5.5
0315 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0316 Description: (RW) Access the selected single shot control register.
0317
0318 What: /sys/bus/coresight/devices/etm<N>/sshot_status
0319 Date: December 2019
0320 KernelVersion: 5.5
0321 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0322 Description: (Read) Print the current value of the selected single shot
0323 status register.
0324
0325 What: /sys/bus/coresight/devices/etm<N>/sshot_pe_ctrl
0326 Date: December 2019
0327 KernelVersion: 5.5
0328 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0329 Description: (RW) Access the selected single show PE comparator control
0330 register.
0331
0332 What: /sys/bus/coresight/devices/etm<N>/mgmt/trcoslsr
0333 Date: April 2015
0334 KernelVersion: 4.01
0335 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0336 Description: (Read) Print the content of the OS Lock Status Register (0x304).
0337 The value it taken directly from the HW.
0338
0339 What: /sys/bus/coresight/devices/etm<N>/mgmt/trcpdcr
0340 Date: April 2015
0341 KernelVersion: 4.01
0342 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0343 Description: (Read) Print the content of the Power Down Control Register
0344 (0x310). The value is taken directly from the HW.
0345
0346 What: /sys/bus/coresight/devices/etm<N>/mgmt/trcpdsr
0347 Date: April 2015
0348 KernelVersion: 4.01
0349 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0350 Description: (Read) Print the content of the Power Down Status Register
0351 (0x314). The value is taken directly from the HW.
0352
0353 What: /sys/bus/coresight/devices/etm<N>/mgmt/trclsr
0354 Date: April 2015
0355 KernelVersion: 4.01
0356 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0357 Description: (Read) Print the content of the SW Lock Status Register
0358 (0xFB4). The value is taken directly from the HW.
0359
0360 What: /sys/bus/coresight/devices/etm<N>/mgmt/trcauthstatus
0361 Date: April 2015
0362 KernelVersion: 4.01
0363 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0364 Description: (Read) Print the content of the Authentication Status Register
0365 (0xFB8). The value is taken directly from the HW.
0366
0367 What: /sys/bus/coresight/devices/etm<N>/mgmt/trcdevid
0368 Date: April 2015
0369 KernelVersion: 4.01
0370 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0371 Description: (Read) Print the content of the Device ID Register
0372 (0xFC8). The value is taken directly from the HW.
0373
0374 What: /sys/bus/coresight/devices/etm<N>/mgmt/trcdevarch
0375 Date: January 2021
0376 KernelVersion: 5.12
0377 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0378 Description: (Read) Print the content of the Device Architecture Register
0379 (offset 0xFBC). The value is taken directly read
0380 from the HW.
0381
0382 What: /sys/bus/coresight/devices/etm<N>/mgmt/trcdevtype
0383 Date: April 2015
0384 KernelVersion: 4.01
0385 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0386 Description: (Read) Print the content of the Device Type Register
0387 (0xFCC). The value is taken directly from the HW.
0388
0389 What: /sys/bus/coresight/devices/etm<N>/mgmt/trcpidr0
0390 Date: April 2015
0391 KernelVersion: 4.01
0392 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0393 Description: (Read) Print the content of the Peripheral ID0 Register
0394 (0xFE0). The value is taken directly from the HW.
0395
0396 What: /sys/bus/coresight/devices/etm<N>/mgmt/trcpidr1
0397 Date: April 2015
0398 KernelVersion: 4.01
0399 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0400 Description: (Read) Print the content of the Peripheral ID1 Register
0401 (0xFE4). The value is taken directly from the HW.
0402
0403 What: /sys/bus/coresight/devices/etm<N>/mgmt/trcpidr2
0404 Date: April 2015
0405 KernelVersion: 4.01
0406 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0407 Description: (Read) Print the content of the Peripheral ID2 Register
0408 (0xFE8). The value is taken directly from the HW.
0409
0410 What: /sys/bus/coresight/devices/etm<N>/mgmt/trcpidr3
0411 Date: April 2015
0412 KernelVersion: 4.01
0413 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0414 Description: (Read) Print the content of the Peripheral ID3 Register
0415 (0xFEC). The value is taken directly from the HW.
0416
0417 What: /sys/bus/coresight/devices/etm<N>/mgmt/trcconfig
0418 Date: February 2016
0419 KernelVersion: 4.07
0420 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0421 Description: (Read) Print the content of the trace configuration register
0422 (0x010) as currently set by SW.
0423
0424 What: /sys/bus/coresight/devices/etm<N>/mgmt/trctraceid
0425 Date: February 2016
0426 KernelVersion: 4.07
0427 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0428 Description: (Read) Print the content of the trace ID register (0x040).
0429
0430 What: /sys/bus/coresight/devices/etm<N>/trcidr/trcidr0
0431 Date: April 2015
0432 KernelVersion: 4.01
0433 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0434 Description: (Read) Returns the tracing capabilities of the trace unit (0x1E0).
0435 The value is taken directly from the HW.
0436
0437 What: /sys/bus/coresight/devices/etm<N>/trcidr/trcidr1
0438 Date: April 2015
0439 KernelVersion: 4.01
0440 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0441 Description: (Read) Returns the tracing capabilities of the trace unit (0x1E4).
0442 The value is taken directly from the HW.
0443
0444 What: /sys/bus/coresight/devices/etm<N>/trcidr/trcidr2
0445 Date: April 2015
0446 KernelVersion: 4.01
0447 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0448 Description: (Read) Returns the maximum size of the data value, data address,
0449 VMID, context ID and instuction address in the trace unit
0450 (0x1E8). The value is taken directly from the HW.
0451
0452 What: /sys/bus/coresight/devices/etm<N>/trcidr/trcidr3
0453 Date: April 2015
0454 KernelVersion: 4.01
0455 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0456 Description: (Read) Returns the value associated with various resources
0457 available to the trace unit. See the Trace Macrocell
0458 architecture specification for more details (0x1E8).
0459 The value is taken directly from the HW.
0460
0461 What: /sys/bus/coresight/devices/etm<N>/trcidr/trcidr4
0462 Date: April 2015
0463 KernelVersion: 4.01
0464 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0465 Description: (Read) Returns how many resources the trace unit supports (0x1F0).
0466 The value is taken directly from the HW.
0467
0468 What: /sys/bus/coresight/devices/etm<N>/trcidr/trcidr5
0469 Date: April 2015
0470 KernelVersion: 4.01
0471 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0472 Description: (Read) Returns how many resources the trace unit supports (0x1F4).
0473 The value is taken directly from the HW.
0474
0475 What: /sys/bus/coresight/devices/etm<N>/trcidr/trcidr8
0476 Date: April 2015
0477 KernelVersion: 4.01
0478 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0479 Description: (Read) Returns the maximum speculation depth of the instruction
0480 trace stream. (0x180). The value is taken directly from the HW.
0481
0482 What: /sys/bus/coresight/devices/etm<N>/trcidr/trcidr9
0483 Date: April 2015
0484 KernelVersion: 4.01
0485 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0486 Description: (Read) Returns the number of P0 right-hand keys that the trace unit
0487 can use (0x184). The value is taken directly from the HW.
0488
0489 What: /sys/bus/coresight/devices/etm<N>/trcidr/trcidr10
0490 Date: April 2015
0491 KernelVersion: 4.01
0492 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0493 Description: (Read) Returns the number of P1 right-hand keys that the trace unit
0494 can use (0x188). The value is taken directly from the HW.
0495
0496 What: /sys/bus/coresight/devices/etm<N>/trcidr/trcidr11
0497 Date: April 2015
0498 KernelVersion: 4.01
0499 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0500 Description: (Read) Returns the number of special P1 right-hand keys that the
0501 trace unit can use (0x18C). The value is taken directly from
0502 the HW.
0503
0504 What: /sys/bus/coresight/devices/etm<N>/trcidr/trcidr12
0505 Date: April 2015
0506 KernelVersion: 4.01
0507 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0508 Description: (Read) Returns the number of conditional P1 right-hand keys that
0509 the trace unit can use (0x190). The value is taken directly
0510 from the HW.
0511
0512 What: /sys/bus/coresight/devices/etm<N>/trcidr/trcidr13
0513 Date: April 2015
0514 KernelVersion: 4.01
0515 Contact: Mathieu Poirier <mathieu.poirier@linaro.org>
0516 Description: (Read) Returns the number of special conditional P1 right-hand keys
0517 that the trace unit can use (0x194). The value is taken
0518 directly from the HW.
