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SPDX-License-Identifier: GPL-2.02 3=============================================4CoreSight Embedded Cross Trigger (CTI & CTM).5=============================================6 7 :Author: Mike Leach <mike.leach@linaro.org>8 :Date: November 20199 10Hardware Description11--------------------12 13The CoreSight Cross Trigger Interface (CTI) is a hardware device that takes14individual input and output hardware signals known as triggers to and from15devices and interconnects them via the Cross Trigger Matrix (CTM) to other16devices via numbered channels, in order to propagate events between devices.17 18e.g.::19 20 0000000 in_trigs :::::::21 0 C 0----------->: : +======>(other CTI channel IO)22 0 P 0<-----------: : v23 0 U 0 out_trigs : : Channels ***** :::::::24 0000000 : CTI :<=========>*CTM*<====>: CTI :---+25 ####### in_trigs : : (id 0-3) ***** ::::::: v26 # ETM #----------->: : ^ #######27 # #<-----------: : +---# ETR #28 ####### out_trigs ::::::: #######29 30The CTI driver enables the programming of the CTI to attach triggers to31channels. When an input trigger becomes active, the attached channel will32become active. Any output trigger attached to that channel will also33become active. The active channel is propagated to other CTIs via the CTM,34activating connected output triggers there, unless filtered by the CTI35channel gate.36 37It is also possible to activate a channel using system software directly38programming registers in the CTI.39 40The CTIs are registered by the system to be associated with CPUs and/or other41CoreSight devices on the trace data path. When these devices are enabled the42attached CTIs will also be enabled. By default/on power up the CTIs have43no programmed trigger/channel attachments, so will not affect the system44until explicitly programmed.45 46The hardware trigger connections between CTIs and devices is implementation47defined, unless the CPU/ETM combination is a v8 architecture, in which case48the connections have an architecturally defined standard layout.49 50The hardware trigger signals can also be connected to non-CoreSight devices51(e.g. UART), or be propagated off chip as hardware IO lines.52 53All the CTI devices are associated with a CTM. On many systems there will be a54single effective CTM (one CTM, or multiple CTMs all interconnected), but it is55possible that systems can have nets of CTIs+CTM that are not interconnected by56a CTM to each other. On these systems a CTM index is declared to associate57CTI devices that are interconnected via a given CTM.58 59Sysfs files and directories60---------------------------61 62The CTI devices appear on the existing CoreSight bus alongside the other63CoreSight devices::64 65 >$ ls /sys/bus/coresight/devices66 cti_cpu0 cti_cpu2 cti_sys0 etm0 etm2 funnel0 replicator0 tmc_etr067 cti_cpu1 cti_cpu3 cti_sys1 etm1 etm3 funnel1 tmc_etf0 tpiu068 69The ``cti_cpu<N>`` named CTIs are associated with a CPU, and any ETM used by70that core. The ``cti_sys<N>`` CTIs are general system infrastructure CTIs that71can be associated with other CoreSight devices, or other system hardware72capable of generating or using trigger signals.::73 74 >$ ls /sys/bus/coresight/devices/etm0/cti_cpu075 channels ctmid enable nr_trigger_cons mgmt power powered regs76 connections subsystem triggers0 triggers1 uevent77 78*Key file items are:-*79 * ``enable``: enables/disables the CTI. Read to determine current state.80 If this shows as enabled (1), but ``powered`` shows unpowered (0), then81 the enable indicates a request to enabled when the device is powered.82 * ``ctmid`` : associated CTM - only relevant if system has multiple CTI+CTM83 clusters that are not interconnected.84 * ``nr_trigger_cons`` : total connections - triggers<N> directories.85 * ``powered`` : Read to determine if the CTI is currently powered.86 87*Sub-directories:-*88 * ``triggers<N>``: contains list of triggers for an individual connection.89 * ``channels``: Contains the channel API - CTI main programming interface.90 * ``regs``: Gives access to the raw programmable CTI regs.91 * ``mgmt``: the standard CoreSight management registers.92 * ``connections``: Links to connected *CoreSight* devices. The number of93 links can be 0 to ``nr_trigger_cons``. Actual number given by ``nr_links``94 in this directory.95 96 97triggers<N> directories98~~~~~~~~~~~~~~~~~~~~~~~99 100Individual trigger connection information. This describes trigger signals for101CoreSight and non-CoreSight connections.102 103Each triggers directory has a set of parameters describing the triggers for104the connection.105 106 * ``name`` : name of connection107 * ``in_signals`` : input trigger signal indexes used in this connection.108 * ``in_types`` : functional types for in signals.109 * ``out_signals`` : output trigger signals for this connection.110 * ``out_types`` : functional types for out signals.111 112e.g::113 114 >$ ls ./cti_cpu0/triggers0/115 in_signals in_types name out_signals out_types116 >$ cat ./cti_cpu0/triggers0/name117 cpu0118 >$ cat ./cti_cpu0/triggers0/out_signals119 0-2120 >$ cat ./cti_cpu0/triggers0/out_types121 pe_edbgreq pe_dbgrestart pe_ctiirq122 >$ cat ./cti_cpu0/triggers0/in_signals123 0-1124 >$ cat ./cti_cpu0/triggers0/in_types125 pe_dbgtrigger pe_pmuirq126 127If a connection has zero signals in either the 'in' or 'out' triggers then128those parameters will be omitted.129 130Channels API Directory131~~~~~~~~~~~~~~~~~~~~~~132 133This provides an easy way to attach triggers to channels, without needing134the multiple register operations that are required if manipulating the135'regs' sub-directory elements directly.136 137A number of files provide this API::138 139 >$ ls ./cti_sys0/channels/140 chan_clear chan_inuse chan_xtrigs_out trigin_attach141 chan_free chan_pulse chan_xtrigs_reset trigin_detach142 chan_gate_disable chan_set chan_xtrigs_sel trigout_attach143 chan_gate_enable chan_xtrigs_in trig_filter_enable trigout_detach144 trigout_filtered145 146Most access to these elements take the form::147 148 echo <chan> [<trigger>] > /<device_path>/<operation>149 150where the optional <trigger> is only needed for trigXX_attach | detach151operations.152 153e.g.::154 155 >$ echo 0 1 > ./cti_sys0/channels/trigout_attach156 >$ echo 0 > ./cti_sys0/channels/chan_set157 158Attaches trigout(1) to channel(0), then activates channel(0) generating a159set state on cti_sys0.trigout(1)160 161 162*API operations*163 164 * ``trigin_attach, trigout_attach``: Attach a channel to a trigger signal.165 * ``trigin_detach, trigout_detach``: Detach a channel from a trigger signal.166 * ``chan_set``: Set the channel - the set state will be propagated around167 the CTM to other connected devices.168 * ``chan_clear``: Clear the channel.169 * ``chan_pulse``: Set the channel for a single CoreSight clock cycle.170 * ``chan_gate_enable``: Write operation sets the CTI gate to propagate171 (enable) the channel to other devices. This operation takes a channel172 number. CTI gate is enabled for all channels by default at power up. Read173 to list the currently enabled channels on the gate.174 * ``chan_gate_disable``: Write channel number to disable gate for that175 channel.176 * ``chan_inuse``: Show the current channels attached to any signal177 * ``chan_free``: Show channels with no attached signals.178 * ``chan_xtrigs_sel``: write a channel number to select a channel to view,179 read to show the selected channel number.180 * ``chan_xtrigs_in``: Read to show the input triggers attached to181 the selected view channel.182 * ``chan_xtrigs_out``:Read to show the output triggers attached to183 the selected view channel.184 * ``trig_filter_enable``: Defaults to enabled, disable to allow potentially185 dangerous output signals to be set.186 * ``trigout_filtered``: Trigger out signals that are prevented from being187 set if filtering ``trig_filter_enable`` is enabled. One use is to prevent188 accidental ``EDBGREQ`` signals stopping a core.189 * ``chan_xtrigs_reset``: Write 1 to clear all channel / trigger programming.190 Resets device hardware to default state.191 192 193The example below attaches input trigger index 1 to channel 2, and output194trigger index 6 to the same channel. It then examines the state of the195channel / trigger connections using the appropriate sysfs attributes.196 197The settings mean that if either input trigger 1, or channel 2 go active then198trigger out 6 will go active. We then enable the CTI, and use the software199channel control to activate channel 2. We see the active channel on the200``choutstatus`` register and the active signal on the ``trigoutstatus``201register. Finally clearing the channel removes this.202 203e.g.::204 205 .../cti_sys0/channels# echo 2 1 > trigin_attach206 .../cti_sys0/channels# echo 2 6 > trigout_attach207 .../cti_sys0/channels# cat chan_free208 0-1,3209 .../cti_sys0/channels# cat chan_inuse210 2211 .../cti_sys0/channels# echo 2 > chan_xtrigs_sel212 .../cti_sys0/channels# cat chan_xtrigs_trigin213 1214 .../cti_sys0/channels# cat chan_xtrigs_trigout215 6216 .../cti_sys0/# echo 1 > enable217 .../cti_sys0/channels# echo 2 > chan_set218 .../cti_sys0/channels# cat ../regs/choutstatus219 0x4220 .../cti_sys0/channels# cat ../regs/trigoutstatus221 0x40222 .../cti_sys0/channels# echo 2 > chan_clear223 .../cti_sys0/channels# cat ../regs/trigoutstatus224 0x0225 .../cti_sys0/channels# cat ../regs/choutstatus226 0x0227