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+ETMv4 sysfs linux driver programming reference - v2.
+====================================================
+
+Supplement to existing ETMv4 driver documentation.
+
+Sysfs files and directories
+---------------------------
+
+Root: /sys/bus/coresight/devices/etm<N>
+
+
+The following paragraphs explain the association between sysfs files and the
+ETMv4 registers that they effect. Note the register names are given without
+the ‘TRC’ prefix.
+
+File		: mode (rw)
+Trace Registers	: {CONFIGR + others}
+Notes		: Bit select trace features. See ‘mode’ section below. Bits
+		in this will cause equivalent programming of trace config and
+		other registers to enable the features requested.
+Syntax & eg	: 'echo bitfield > mode'
+		bitfield up to 32 bits setting trace features.
+Example		: $> echo 0x > mode
+
+File		: reset (wo)
+Trace Registers	: All
+Notes		: Reset all programming to trace nothing / no logic programmed.
+Syntax		: 'echo 1 > reset'
+
+File		: enable_source (wo)
+Trace Registers	: PRGCTLR, All hardware regs.
+Notes		:  >0: Programs up the hardware with the current values held in
+		the driver and enables trace.
+		0: disable trace hardware.
+Syntax		: 'echo 1 > enable_source'
+
+File		: cpu (ro)
+Trace Registers	: None.
+Notes		: CPU ID that this ETM is attached to.
+Example		:$> cat cpu
+		$> 0
+
+File		: addr_idx (rw)
+Trace Registers	: None.
+Notes		: Virtual register to index address comparator and range
+		features. Set index for first of the pair in a range.
+Syntax		: 'echo idx > addr_idx'
+		Where idx <  nr_addr_cmp x 2
+
+File		: addr_range (rw)
+Trace Registers	: ACVR[idx, idx+1], VIIECTLR
+Notes		: Pair of addresses for a range selected by addr_idx. Include
+		/ exclude according to the optional parameter, or if omitted
+		uses the current ‘mode’ setting. Select comparator range in
+		control register. Error if index is odd value.
+Depends		: mode, addr_idx
+Syntax		: 'echo addr1 addr2 [exclude] > addr_range'
+		Where addr1 and addr2 define the range and addr1 < addr2.
+		Optional exclude value - 0 for include, 1 for exclude.
+Example		: $> echo 0x0000 0x2000 0 > addr_range
+
+File		: addr_single (rw)
+Trace Registers	: ACVR[idx]
+Notes		: Set a single address comparator according to addr_idx. This
+		is used if the address comparator is used as part of event
+		generation logic etc.
+Depends		: addr_idx
+Syntax		: 'echo addr1 > addr_single'
+
+File		: addr_start (rw)
+Trace Registers	: ACVR[idx], VISSCTLR
+Notes		: Set a trace start address comparator according to addr_idx.
+		Select comparator in control register.
+Depends		: addr_idx
+Syntax		: 'echo addr1 > addr_start'
+
+File		: addr_stop (rw)
+Trace Registers	: ACVR[idx], VISSCTLR
+Notes		: Set a trace stop address comparator according to addr_idx.
+		Select comparator in control register.
+Depends		: addr_idx
+Syntax		: 'echo addr1 > addr_stop'
+
+File		: addr_context (rw)
+Trace Registers	: ACATR[idx,{6:4}]
+Notes		: Link context ID comparator to address comparator addr_idx
+Depends		: addr_idx.
+Syntax		: 'echo ctxt_idx > addr_context'
+		Where ctxt_idx is the index of the linked context id / vmid
+		comparator.
+
+File		: addr_ctxtype (rw)
+Trace Registers	: ACATR[idx,{3:2}]
+Notes		: Input value string. Set type for linked context ID comparator
+Depends		: addr_idx
+Syntax		: 'echo type > addr_ctxtype'
+		Type one of {all, vmid, ctxid, none}
+Example		: $> echo ctxid > addr_ctxtype
+
+File		: addr_exlevel_s_ns (rw)
+Trace Registers	: ACATR[idx,{14:8}]
+Notes		: Set the ELx secure and non-secure matching bits for the
+		selected address comparator
+Depends		: addr_idx
+Syntax		: 'echo val > addr_exlevel_s_ns'
+		val is a 7 bit value for exception levels to exclude. Input
+		value shifted to correct bits in register.
+Example		: $> echo 0x4F > addr_exlevel_s_ns
+
+File		: addr_instdatatype (rw)
+Trace Registers	: ACATR[idx,{1:0}]
+Notes		: Set the comparator address type for matching. Driver only
+		supports setting instruction address type.
+Depends		: addr_idx
+
+File		: addr_cmp_view (ro)
+Trace Registers	: ACVR[idx, idx+1], ACATR[idx], VIIECTLR
+Notes		: Read the currently selected address comparator. If part of
+		address range then display both addresses.
+Depends		: addr_idx
+Syntax		: 'cat addr_cmp_view'
+Example		: $> cat addr_cmp_view
+		addr_cmp[0] range 0x0 0xffffffffffffffff include ctrl(0x4b00)
+
+File		: nr_addr_cmp (ro)
+Trace Registers	: From IDR4
+Notes		: Number of address comparator pairs
+
+File		: sshot_idx (rw)
+Trace Registers	: None
+Notes		: Select  single shot register set.
+
+File		: sshot_ctrl (rw)
+Trace Registers	: SSCCR[idx]
+Notes		: Access a single shot comparator control register.
+Depends		: sshot_idx
+Syntax		: 'echo val > sshot_ctrl'
+		Writes val into the selected control register.
+
+File		: sshot_status (ro)
+Trace Registers	: SSCSR[idx]
+Notes		: Read a single shot comparator status register
+Depends		: sshot_idx
+Syntax		: 'cat sshot_status'
+		Read status.
+Example		: $> cat sshot_status
+		0x1
+
+File		: sshot_pe_ctrl (rw)
+Trace Registers	: SSPCICR[idx]
+Notes		: Access a single shot PE comparator input control register.
+Depends		: sshot_idx
+Syntax		: echo val > sshot_pe_ctrl
+		Writes val into the selected control register.
+
+File		: ns_exlevel_vinst (rw)
+Trace Registers	: VICTLR{23:20}
+Notes		: Program non-secure exception level filters. Set / clear NS
+		exception filter bits. Setting ‘1’ excludes trace from the
+		exception level.
+Syntax		: 'echo bitfield > ns_exlevel_viinst'
+		Where bitfield contains bits to set clear for EL0 to EL2
+Example		: %> echo 0x4 > ns_exlevel_viinst
+		; Exclude EL2 NS trace.
+
+File		: vinst_pe_cmp_start_stop (rw)
+Trace Registers	: VIPCSSCTLR
+Notes		: Access PE start stop comparator input control registers
+
+File		: bb_ctrl (rw)
+Trace Registers	: BBCTLR
+Notes		: Define ranges that Branch Broadcast will operate in.
+		Default (0x0) is all addresses.
+Depends		: BB enabled.
+
+File		: cyc_threshold (rw)
+Trace Registers	: CCCTLR
+Notes		: Set the threshold for which cycle counts will be emitted.
+		Error if attempt to set below minimum defined in IDR3, masked
+		to width of valid bits.
+Depends		: CC enabled.
+
+File		: syncfreq (rw)
+Trace Registers	: SYNCPR
+Notes		: Set trace synchronisation period. Power of 2 value, 0 (off)
+		or 8-20. Driver defaults to 12 (every 4096 bytes).
+
+File		: cntr_idx (rw)
+Trace Registers	: none
+Notes		: Select the counter to access
+Syntax		: 'echo idx > cntr_idx'
+		Where idx <  nr_cntr
+
+File		: cntr_ctrl (rw)
+Trace Registers	: CNTCTLR[idx]
+Notes		: Set counter control value
+Depends		: cntr_idx
+Syntax		: 'echo val > cntr_ctrl'
+		Where val is per ETMv4 spec.
+
+File		: cntrldvr (rw)
+Trace Registers	: CNTRLDVR[idx]
+Notes		: Set counter reload value
+Depends		: cntr_idx
+Syntax		: 'echo val > cntrldvr'
+		Where val is per ETMv4 spec.
+
+File		: nr_cntr (ro)
+Trace Registers	: From IDR5
+Notes		: Number of counters implemented.
+
+File		: ctxid_idx (rw)
+Trace Registers	: None
+Notes		: Select the context ID comparator to access
+Syntax		: 'echo idx > ctxid_idx'
+		Where idx <  numcidc
+
+File		: ctxid_pid (rw)
+Trace Registers	: CIDCVR[idx]
+Notes		: Set the context ID comparator value
+Depends		: ctxid_idx
+
+File		: ctxid_masks (rw)
+Trace Registers	: CIDCCTLR0, CIDCCTLR1, CIDCVR<0-7>
+Notes		: Pair of values to set the byte masks for 1-8 context ID
+		comparators. Automatically clears masked bytes to 0 in CID
+		value registers.
+Syntax		: 'echo m3m2m1m0 [m7m6m5m4] > ctxid_masks'
+		32 bit values made up of mask bytes, where mN represents a
+		byte mask value for Ctxt ID comparator N.
+		Second value not required on systems that have fewer than 4
+		context ID comparators
+
+File		: numcidc (ro)
+Trace Registers	: From IDR4
+Notes		: Number of Context ID comparators
+
+File		: vmid_idx (rw)
+Trace Registers	: None
+Notes		: Select the VM ID comparator to access.
+Syntax		: 'echo idx > vmid_idx'
+		Where idx <  numvmidc
+
+File		: vmid_val (rw)
+Trace Registers	: VMIDCVR[idx]
+Notes		: Set the VM ID comparator value
+Depends		: vmid_idx
+
+File		: vmid_masks (rw)
+Trace Registers	: VMIDCCTLR0, VMIDCCTLR1, VMIDCVR<0-7>
+Notes		: Pair of values to set the byte masks for 1-8 VM ID
+		comparators. Automatically clears masked bytes to 0 in VMID
+		value registers.
+Syntax		: 'echo m3m2m1m0 [m7m6m5m4] > vmid_masks'
+		Where mN represents a byte mask value for VMID comparator N.
+		Second value not required on systems that have fewer than
+		4 VMID comparators.
+
+File		: numvmidc (ro)
+Trace Registers	: From IDR4
+Notes		: Number of VMID comparators
+
+File		: res_idx (rw)
+Trace Registers	: None.
+Notes		: Select the resource selector control to access. Must be 2 or
+		higher as selectors 0 and 1 are hardwired.
+Syntax		: 'echo idx > res_idx'
+		Where 2 <= idx < nr_resource x 2
+
+File		: res_ctrl (rw)
+Trace Registers	: RSCTLR[idx]
+Notes		: Set resource selector control value. Value per ETMv4 spec.
+Depends		: res_idx
+Syntax		: 'echo val > res_cntr'
+		Where val is per ETMv4 spec.
+
+File		: nr_resource (ro)
+Trace Registers	: From IDR4
+Notes		: Number of resource selector pairs
+
+File		: event (rw)
+Trace Registers	: EVENTCTRL0R
+Notes		: Set up to 4 implemented event fields.
+Syntax		: 'echo ev3ev2ev1ev0 > event'
+		Where evN is an 8 bit event field. Up to 4 event fields make up
+		the 32bit input value. Number of valid fields implementation
+		dependent defined in IDR0.
+
+File		: event_instren (rw)
+Trace Registers	: EVENTCTRL1R
+Notes		: Choose events which insert event packets into trace stream.
+Depends		: EVENTCTRL0R
+Syntax		: 'echo bitfield > event_instren'
+		Where bitfield is up to 4 bits according to number of event
+		fields.
+
+File		: event_ts (rw)
+Trace Registers	: TSCTLR
+Notes		: Set the event that will generate timestamp requests.
+Depends		: TS activated
+Syntax		: 'echo evfield > event_ts'
+		Where evfield is an 8 bit event selector.
+
+File		: seq_idx (rw)
+Trace Registers	: None
+Notes		: Sequencer event register select - 0 to 2
+
+
+File		: seq_state (rw)
+Trace Registers	: SEQSTR
+Notes		: Sequencer current state - 0 to 3.
+
+File		: seq_event (rw)
+Trace Registers	: SEQEVR[idx]
+Notes		: State transition event registers
+Depends		: seq_idx
+Syntax		: 'echo evBevF > seq_event'
+		Where evBevF is a 16 bit value made up of two event selectors,
+		evB - back, evF - forwards.
+
+File		: seq_reset_event (rw)
+Trace Registers	: SEQRSTEVR
+Notes		: Sequencer reset event
+Syntax		: 'echo evfield > seq_reset_event'
+		Where evfield is an 8 bit event selector.
+
+File		: nrseqstate (ro)
+Trace Registers	: From IDR5
+Notes		: Number of sequencer states (0 or 4)
+
+File		: nr_pe_cmp (ro)
+Trace Registers	: From IDR4
+Notes		: Number of PE comparator inputs
+
+File		: nr_ext_inp (ro)
+Trace Registers	: From IDR5
+Notes		: Number of external inputs
+
+File		: nr_ss_cmp (ro)
+Trace Registers	: From IDR4
+Notes		: Number of Single Shot control registers
+
+Note: When programming any address comparator the driver will tag the
+comparator with a type used - i.e. RANGE, SINGLE, START, STOP. Once this tag
+is set, then only the values can be changed using the same sysfs file / type
+used to program it.
+
+Thus:-
+% echo 0 > addr_idx		    ; select address comparator 0
+% echo 0x1000 0x5000 0 > addr_range ; set address range on comparators 0 and 1.
+% echo 0x2000 > addr_start	    ; this will error as comparator 0 is a
+				    ; range comparator
+% echo 2 > addr_idx		    ; select address comparator 2
+% echo 0x2000 > addr_start	    ; this is OK as comparator 2 is unused,
+% echo 0x3000 > addr_stop	    ; this will error as comparator 2 a start
+				    ; address comparator
+% echo 2 > addr_idx		    ; select address comparator 3
+% echo 0x3000 > addr_stop	    ; this is OK
+
+To remove programming on all the comparators (and all the other hardware) use
+the reset parameter:
+
+% echo 1 > reset
+
+The ‘mode’ sysfs parameter.
+---------------------------
+
+This is a bitfield selection parameter that sets the overall trace mode for the
+ETM. The table below describes the bits, using the defines from the driver
+source file, along with a description of the feature these represent. Many
+features are optional and therefore dependent on implementation in the
+hardware.
+
+Bit assignements shown below:-
+
+bit (0)	    : #define ETM_MODE_EXCLUDE
+description : This is the default value for the include / exclude function when
+	      setting address ranges. Set 1 for exclude range. When the mode
+	      parameter is set this value is applied to the currently indexed
+	      address range.
+
+bit (4)	    : #define ETM_MODE_BB
+description : Set to enable branch broadcast if supported in hardware [IDR0].
+
+bit (5)	    : #define ETMv4_MODE_CYCACC
+description : Set to enable cycle accurate trace if supported [IDR0].
+
+bit (6)	    : ETMv4_MODE_CTXID
+description : Set to enable context ID tracing if supported in hardware [IDR2].
+
+bit (7)	    : ETM_MODE_VMID
+description : Set to enable virtual machine ID tracing if supported [IDR2].
+
+bit (11)    : ETMv4_MODE_TIMESTAMP
+description : Set to enable timestamp generation if supported [IDR0].
+
+bit (12)    : ETM_MODE_RETURNSTACK
+description : Set to enable trace return stack use if supported [IDR0].
+
+bit (13-14) : ETM_MODE_QELEM(val)
+description : ‘val’ determines level of Q element support enabled if
+	    implemented by the ETM [IDR0]
+
+bit (19)    : ETM_MODE_ATB_TRIGGER
+description : Set to enable the ATBTRIGGER bit in the event control register
+	    [EVENTCTLR1] if supported [IDR5].
+
+bit (20)    : ETM_MODE_LPOVERRIDE
+description : Set to enable the LPOVERRIDE bit in the event control register
+	    [EVENTCTLR1], if supported [IDR5].
+
+bit (21)    : ETM_MODE_ISTALL_EN
+description : Set to enable the ISTALL bit in the stall control register
+	    [STALLCTLR]
+
+bit (23)    : ETM_MODE_INSTPRIO
+description : Set to enable the INSTPRIORITY bit in the stall control register
+	    [STALLCTLR] , if supported [IDR0].
+
+bit (24)    : ETM_MODE_NOOVERFLOW
+description : Set to enable the NOOVERFLOW bit in the stall control register
+	    [STALLCTLR], if supported [IDR3].
+
+bit (25)    : ETM_MODE_TRACE_RESET
+description : Set to enable the TRCRESET bit in the viewinst control register
+	    [VICTLR] , if supported [IDR3].
+
+bit (26)    : ETM_MODE_TRACE_ERR
+description : Set to enable the TRCCTRL bit in the viewinst control register
+	    [VICTLR].
+
+bit (27)    : ETM_MODE_VIEWINST_STARTSTOP
+description : Set the initial state value of the ViewInst start / stop logic
+	    in the viewinst control register [VICTLR]
+
+bit (30)    : ETM_MODE_EXCL_KERN
+description : Set default trace setup to exclude kernel mode trace (see note a)
+
+bit (31)    : ETM_MODE_EXCL_USER
+description : Set default trace setup to exclude user space trace (see note a)
+
+Note a) On startup the ETM is programmed to trace the complete address space
+using address range comparator 0. ‘mode’ bits 30 / 31 modify this setting to
+set EL exclude bits for NS state in either user space (EL0) or kernel space
+(EL1) in the address range comparator. (the default setting excludes all
+secure EL, and NS EL2)
+
+Once the reset parameter has been used, and/or custom programming has been
+implemented - using these bits will result in the EL bits for address
+comparator 0 being set in the same way.
+
+Note b) Bits 2-3, 8-10, 15-16, 18, 22, control features that only work with
+data trace. As A profile data trace is architecturally prohibited in ETMv4,
+these have been omitted here. Possible uses could be where a kernel has
+support for control of R or M profile infrastructure as part of a heterogeneous
+system.
+
+Bits 17, 28-29 are unused.
