coresight: etm4x: docs: Adds detailed document for programming etm4x.

Add in detailed programmers reference for users wanting to program the
CoreSight ETM 4.x driver using sysfs.

Signed-off-by: Mike Leach <[e-mail]>
Reviewed-by: Mathieu Poirier <[e-mail]>
Signed-off-by: Jonathan Corbet <[e-mail]>

Documentation/trace/coresight/coresight-etm4x-reference.rst

···
+===============================================
+ETMv4 sysfs linux driver programming reference.
+===============================================
+
+    :Author:   Mike Leach <[e-mail]>
+    :Date:     October 11th, 2019
+
+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:
+    ``$> echo 0x012 > mode``
+
+----
+
+:File:            ``reset`` (wo)
+:Trace Registers: All
+:Notes:
+    Reset all programming to trace nothing / no logic programmed.
+
+:Syntax:
+    ``echo 1 > reset``
+
+----
+
+:File:            ``enable_source`` (wo)
+:Trace Registers: PRGCTLR, All hardware regs.
+:Notes:
+    - > 0 : Programs up the hardware with the current values held in the driver
+      and enables trace.
+
+    - = 0 : disable trace hardware.
+
+:Syntax:
+    ``echo 1 > enable_source``
+
+----
+
+:File:            ``cpu`` (ro)
+:Trace Registers: None.
+:Notes:
+    CPU ID that this ETM is attached to.
+
+:Example:
+    ``$> 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``
+
+    Excludes 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 Context 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
+    32-bit input value. Number of valid fields is 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, 1.
+  % echo 0x2000 > addr_start    ; 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	; error as comparator 2 set as start address.
+  % 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 assignments shown below:-
+
+----
+
+**bit (0):**
+    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):**
+    ETM_MODE_BB
+
+**description:**
+    Set to enable branch broadcast if supported in hardware [IDR0].
+
+
+**bit (5):**
+    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.