clarify writes to dinfc

src/csv/CHERI_CSR.csv

@@ -43,7 +43,7 @@ direct write if address didn't change","","✔","","","{cheri_default_ext_name},
 "ddc","0x416","","U","URW","<<infinite-cap>>","Apply <<section_invalid_addr_conv>>.
 Always update the CSR with <<SCADDR>> even if the address didn't change.","Apply <<section_invalid_addr_conv>> and update the CSR with the result if the address changed,
 direct write if address didn't change","","✔","","","{cheri_default_ext_name}","User Default Data Capability","","","","","","","","","","","","","","","","","","","","",""
-"dinfc","0x7bd","","D","DRW","<<infinite-cap>>","Ignore","Ignore","","","","✔","Sdext","Source of <<infinite-cap>> capability in debug mode, writes are ignored","","","","","","","","","","","","","","","","","","","","",""
+"dinfc","0x7bd","","D","DRW","<<infinite-cap>>","Ignore","Update <<m_bit>> using <<SCMODE>> semantics.","","","","✔","Sdext","Source of <<infinite-cap>> capability in debug mode, writes are ignored","","","","","","","","","","","","","","","","","","","","",""
 "utidc","0x480","utid","U","Read: U, Write: U, <<asr_perm>>","tag=0, otherwise undefined","Update the CSR using <<SCADDR>>.","direct write","","","","✔","Zstid","User thread ID","","","","","","","","","","","","","","","","","","","","",""
 "stidc","0x580","stid","S","Read: S, Write: S, <<asr_perm>>","tag=0, otherwise undefined","Update the CSR using <<SCADDR>>.","direct write","","","","✔","Zstid","Supervisor thread ID","","","","","","","","","","","","","","","","","","","","",""
 "vstidc","0xA80","vstid","H","Read: VS, Write: VS, <<asr_perm>>","tag=0, otherwise undefined","Update the CSR using <<SCADDR>>.","direct write","","","","✔","Zstid","Virtual supervisor thread ID","","","","","","","","","","","","","","","","","","","","",""

src/debug-integration.adoc

@@ -185,8 +185,12 @@ If {cheri_default_ext_name} is implemented:
 ** This only needs doing once after resetting the core.
 * The <<m_bit>> is used on debug mode entry to determine which CHERI execution mode to enter.
 
-The <<m_bit>> is the only writeable field in <<dinfc>>.
-Therefore if {cheri_default_ext_name} is not implemented then it is read-write with no writeable fields.
+The <<m_bit>> is the only writeable field in <<dinfc>>:
+
+* It is only updated on a <<CSRRW>> write _if_ the capability being written has a valid <<m_bit>>.
+* If any other CSR instruction is used, or if the written <<m_bit>> is not valid then <<dinfc>> is not updated.
+
+If {cheri_default_ext_name} is not implemented then <<dinfc>> is read-write with no writeable fields.
 
 NOTE: A future version of this specification may add writeable fields to allow creation
  of other capabilities, if, for example, a future extension requires multiple formats for