10 Parameters and Discovery
This document defines a number of parameters for describing aspects of the encoder such as the widths of buses, the presence or absence of optional features and the size of resources, as listed in Table 40 and Table 41.
Depending on the implementation, some parameters may be inherently fixed whilst others may be passed in to the design by some means.
Table 40. Parameters to the encoder - instruction trace
| Parameter name | Range | Description |
|---|---|---|
| arch_p | The architecture specification version with which the encoder is compliant (0 for initial version). | |
| blocks_p | Number of times iretire, itype etc. are replicated | |
| bpred_size_p | Number of entries in the branch predictor is 2bpred_size_p. Minimum number of entries is 2, so a value of 0 indicates that there is no branch predictor implemented. | |
| cache_size_p | Number of entries in the jump target cache is 2cache_size_p. Minimum number of entries is 2, so a value of 0 indicates that there is no jump target cache implemented. | |
| call_counter_size_p | Number of bits in the nested call counter is 2call_counter_size_p. Minimum number of entries is 2, so a value of 0 indicates that there is no implicit return call counter implemented. | |
| ctype_width_p | Width of the ctype bus | |
| context_width_p | Width of context bus | |
| time_width_p | Width of time bus | |
| ecause_width_p | Width of exception cause bus | |
| ecause_choice_p | Number of bits of exception cause to match using multiple choice | |
| f0s_width_p | Width of the subformat field in format 0 te_inst packets (see Section 7.8.1). | |
| filter_context_p | 0 or 1 | Filtering on context supported when 1 |
| filter_time_p | 0 or 1 | Filtering on time supported when 1 |
| filter_excint_p | Filtering on exception cause or interrupt supported when non_zero. Number of nested exceptions supported is 2filter_excint_p | |
| filter_privilege_p | 0 or 1 | Filtering on privilege supported when 1 |
| filter_tval_p | 0 or 1 | Filtering on trap value supported when 1 (provided filter_excint_p is non-zero) |
| iaddress_lsb_p | LSB of instruction address bus to trace. 1 if compressed instructions are supported, 2 otherwise | |
| iaddress_width_p | Width of instruction address bus. This is the same as DXLEN | |
| iretire_width_p | Width of the iretire bus | |
| ilastsize_width_p | Width of the ilastsize bus | |
| itype_width_p | Width of the itype bus | |
| nocontext_p | 0 or 1 | Exclude context from te_inst packets if 1 |
| notime_p | 0 or 1 | Exclude time from te_inst packets if 1 |
| privilege_width_p | Width of privilege bus | |
| retires_p | Maximum number of instructions that can be retired per block | |
| return_stack_size_p | Number of entries in the return address stack is 2return_stack_size_p. Minimum number of entries is 2, so a value of 0 indicates that there is no implicit return stack implemented. | |
| sijump_p | 0 or 1 | sijump is used to identify sequentially inferable jumps |
| impdef_width_p | Width of implementation-defined input bus |
Table 41. Parameters to the encoder - data trace
| Parameter name | Range | Description |
|---|---|---|
| daddress_width_p | Width of the daddress bus | |
| dblock_width_p | Width of the dblock bus | |
| data_width_p | Width of the data bus | |
| dsize_width_p | Width of the dsize bus | |
| dtype_width_p | Width of the dtype bus | |
| iaddr_lsbs_width_p | Width of the iaddr_lsbs bus | |
| lrid_width_p | Width of the lrid bus | |
| lresp_width_p | Width of the lresp bus | |
| ldata_width_p | Width of the ldata bus | |
| sdata_width_p | Width of the sdata bus |
10.1 Discovery of encoder parameters
To operate correctly, the decoder must be able to determine some of the encoder’s parameters at runtime, in the form of discoverable attributes. These parameters must be discoverable by the decoder, or else be fixed at the default value (in other words, if an encoder does not make a particular parameter discoverable, it must implement only the default value of that parameter, which the decoder will also use). Table 42 lists the required discoverable attributes for instruction trace.
To access the discoverable attributes, some external entity, for example a debugger or a supervisory hart, must request it from the encoder. The encoder will provide the discovery information in one or more different formats. The preferred format is a packet which is sent over the trace infrastructure. Another format would be allowing the external entity to read the values from some register or memory mapped space maintained by the encoder. Section 10.2 gives an example of how this may be accomplished.
Table 42. Required instruction trace attributes
| Name | Default | Parameter mapping |
|---|---|---|
| arch | 0 | arch_p |
| bpred_size | 0 | bpred_size_p |
| cache_size | 0 | cache_size_p |
| call_counter_size | 0 | call_counter_size_p |
| context_width | 0 | context_width_p - 1 |
| time_width | 0 | time_width_p - 1 |
| ecause_width | 3 | ecause_width_p - 1 |
| f0s_width | 0 | f0s_width_p |
| iaddress_lsb | 0 | iaddress_lsb_p - 1 |
| iaddress_width | 31 | iaddress_width_p - 1 |
| nocontext | 1 | nocontext |
| notime | 1 | notime |
| privilege_width | 1 | privilege_width_p - 1 |
| return_stack_size | 0 | return_stack_size_p |
| sijump | 0 | sijump_p |
For ease of use it is further recommended that all of the encoder’s parameters be mapped to discoverable attributes, even if not directly required by the decoder. In particular, attributes related to filtering capabilities. Table 43 lists the attributes associated with the filtering recommendations discussed in Section 5, Table 44 lists attributes related to other instruction trace parameters mentioned in this document, and Table 45 lists attributes related to data trace.
Table 43. Optional filtering attributes
| Name | Default | Parameter mapping |
|---|---|---|
| comparators | 0 | comparators_p - 1 |
| filters | 0 | filters_p - 1 |
| ecause_choice | 5 | ecause_choice_p |
| filter_context | 1 | filter_context_p |
| filter_time | 1 | filter_time_p |
| filter_excint | 1 | filter_excint_p |
| filter_privilege | 1 | filter_privilegep |
| filter_tval | 1 | filter_tval_p |
Table 44. Other recommended attributes
| Name | Default | Description |
|---|---|---|
| ctype_width | 0 | ctype_width_p - 1 |
| ilastsize_width | 0 | ilastsize_width_p - 1 |
| itype_width | 3 | itype_width_p - 1 |
| iretire_width | 1 | iretire_width_p - 1 |
| retires | 0 | retires_p - 1 |
| impdef_width | 0 | impdef_width_p - 1 |
Table 45. Data trace attributes
| Name | Default | Description |
|---|---|---|
| daddress_width | 31 | daddress_width_p - 1 |
| dblock_width | 0 | dblock_width_p - 1 |
| data_width | 31 | data_width_p - 1 |
| dsize_width | 2 | dsize_width_p - 1 |
| dtype_width | 0 | dtype_width_p - 1 |
| iaddr_lsbs_width | 0 | iaddr_lsbs_width_p - 1 |
| lrid_width | 0 | lrid_width_p - 1 |
| lresp_width | 0 | lresp_width_p - 1 |
| ldata_width | 31 | ldata_width_p - 1 |
| sdata_width | 31 | sdata_width_p - 1 |
10.2 Example ipxact description
This section provides an example of discovery information represented in the ipxact form.
\<?xmlversion="1.0" encoding="UTF-8"?>
\<ipxact:component
xmlns:ipxact="http://www.accellera.org/XMLSchema/IPXACT/1685-2014"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.accellera.org/XMLSchema/IPXACT/1685-2014
http://www.accellera.org/XMLSchema/IPXACT/1685-2014/index.xsd">
\<ipxact:vendor>Siemens\</ipxact:vendor>
\<ipxact:library>TraceEncoder\</ipxact:library>
\<ipxact:name>TraceEncoder\</ipxact:name>
\<ipxact:version>0.8\</ipxact:version>
\<ipxact:memoryMaps>
\<ipxact:memoryMap>
\<ipxact:name>TraceEncoderRegisterMap\</ipxact:name>
\<ipxact:addressBlock>
\<ipxact:name>>TraceEncoderRegisterAddressBlock\</ipxact:name>
\<ipxact:baseAddress>0\</ipxact:baseAddress>
\<ipxact:range>128\</ipxact:range>
\<ipxact:width>64\</ipxact:width>
\<ipxact:register>
\<ipxact:name>discovery_info_0\</ipxact:name>
\<ipxact:addressOffset>'h0\</ipxact:addressOffset>
\<ipxact:size>64\</ipxact:size>
\<ipxact:access>read-only\</ipxact:access>
\<ipxact:field>
\<ipxact:name>version\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>0\</ipxact:bitOffset>
\<ipxact:bitWidth>4\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>minor_revision\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>4\</ipxact:bitOffset>
\<ipxact:bitWidth>4\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>arch\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>8\</ipxact:bitOffset>
\<ipxact:bitWidth>4\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>bpred_size\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>12\</ipxact:bitOffset>
\<ipxact:bitWidth>4\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>cache_size\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>16\</ipxact:bitOffset>
\<ipxact:bitWidth>4\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>call_counter_size\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>20\</ipxact:bitOffset>
\<ipxact:bitWidth>3\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>comparators\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>23\</ipxact:bitOffset>
\<ipxact:bitWidth>3\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>context_type_width\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>26\</ipxact:bitOffset>
\<ipxact:bitWidth>5\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>context_width\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>31\</ipxact:bitOffset>
\<ipxact:bitWidth>5\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>ecause_choice\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>36\</ipxact:bitOffset>
\<ipxact:bitWidth>3\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>ecause_width\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>39\</ipxact:bitOffset>
\<ipxact:bitWidth>4\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>filters\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>43\</ipxact:bitOffset>
\<ipxact:bitWidth>4\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>filter_context\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>47\</ipxact:bitOffset>
\<ipxact:bitWidth>1\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>filter_excint\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>48\</ipxact:bitOffset>
\<ipxact:bitWidth>4\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>filter_privilege\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>52\</ipxact:bitOffset>
\<ipxact:bitWidth>1\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>filter_tval\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>53\</ipxact:bitOffset>
\<ipxact:bitWidth>1\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>filter_impdef\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>54\</ipxact:bitOffset>
\<ipxact:bitWidth>1\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>f0s_width\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>55\</ipxact:bitOffset>
\<ipxact:bitWidth>2\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>iaddress_lsb\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>57\</ipxact:bitOffset>
\<ipxact:bitWidth>2\</ipxact:bitWidth>
\</ipxact:field>
\</ipxact:register>
\<ipxact:register>
\<ipxact:name>discovery_info_1\</ipxact:name>
\<ipxact:addressOffset>'h4\</ipxact:addressOffset>
\<ipxact:size>64\</ipxact:size>
\<ipxact:access>read-only\</ipxact:access>
\<ipxact:field>
\<ipxact:name>iaddress_width\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>0\</ipxact:bitOffset>
\<ipxact:bitWidth>7\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>ilastsize_width\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>7\</ipxact:bitOffset>
\<ipxact:bitWidth>7\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>itype_width\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>14\</ipxact:bitOffset>
\<ipxact:bitWidth>7\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>iretire_width\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>21\</ipxact:bitOffset>
\<ipxact:bitWidth>7\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>nocontext\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>28\</ipxact:bitOffset>
\<ipxact:bitWidth>1\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>privilege_width\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>29\</ipxact:bitOffset>
\<ipxact:bitWidth>2\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>retires\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>31\</ipxact:bitOffset>
\<ipxact:bitWidth>3\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>return_stack_size\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>34\</ipxact:bitOffset>
\<ipxact:bitWidth>4\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>sijump\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>38\</ipxact:bitOffset>
\<ipxact:bitWidth>1\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>taken_branches\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>39\</ipxact:bitOffset>
\<ipxact:bitWidth>4\</ipxact:bitWidth>
\</ipxact:field>
\<ipxact:field>
\<ipxact:name>impdef_width\</ipxact:name>
\<ipxact:description>text\</ipxact:description>
\<ipxact:bitOffset>43\</ipxact:bitOffset>
\<ipxact:bitWidth>5\</ipxact:bitWidth>
\</ipxact:field>
\</ipxact:register>
\</ipxact:addressBlock>
\<ipxact:addressUnitBits>8\</ipxact:addressUnitBits>
\</ipxact:memoryMap>
\</ipxact:memoryMaps>
\</ipxact:component>