target/riscv: debug: Introduce tinfo CSR

tinfo.info:
  One bit for each possible type enumerated in tdata1.
  If the bit is set, then that type is supported by the currently
  selected trigger.

Signed-off-by: Frank Chang <frank.chang@sifive.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: LIU Zhiwei <zhiwei_liu@linux.alibaba.com>
Message-Id: <20220909134215.1843865-6-bmeng.cn@gmail.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/cpu_bits.h

@@ -319,6 +319,7 @@
 #define CSR_TDATA1          0x7a1
 #define CSR_TDATA2          0x7a2
 #define CSR_TDATA3          0x7a3
+#define CSR_TINFO           0x7a4
 
 /* Debug Mode Registers */
 #define CSR_DCSR            0x7b0

target/riscv/csr.c

@@ -3094,6 +3094,13 @@ static RISCVException write_tdata(CPURISCVState *env, int csrno,
     return RISCV_EXCP_NONE;
 }
 
+static RISCVException read_tinfo(CPURISCVState *env, int csrno,
+                                 target_ulong *val)
+{
+    *val = tinfo_csr_read(env);
+    return RISCV_EXCP_NONE;
+}
+
 /*
  * Functions to access Pointer Masking feature registers
  * We have to check if current priv lvl could modify
@@ -3898,6 +3905,7 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
     [CSR_TDATA1]    =  { "tdata1",  debug, read_tdata,   write_tdata   },
     [CSR_TDATA2]    =  { "tdata2",  debug, read_tdata,   write_tdata   },
     [CSR_TDATA3]    =  { "tdata3",  debug, read_tdata,   write_tdata   },
+    [CSR_TINFO]     =  { "tinfo",   debug, read_tinfo,   write_ignore  },
 
     /* User Pointer Masking */
     [CSR_UMTE]    =    { "umte",    pointer_masking, read_umte,  write_umte },

target/riscv/debug.c

@@ -37,9 +37,7 @@
  * - tdata1
  * - tdata2
  * - tdata3
- *
- * We don't support writable 'type' field in the tdata1 register, so there is
- * no need to implement the "tinfo" CSR.
+ * - tinfo
  *
  * The following triggers are implemented:
  *
@@ -372,6 +370,12 @@ void tdata_csr_write(CPURISCVState *env, int tdata_index, target_ulong val)
     }
 }
 
+target_ulong tinfo_csr_read(CPURISCVState *env)
+{
+    /* assume all triggers support the same types of triggers */
+    return BIT(TRIGGER_TYPE_AD_MATCH);
+}
+
 void riscv_cpu_debug_excp_handler(CPUState *cs)
 {
     RISCVCPU *cpu = RISCV_CPU(cs);

target/riscv/debug.h

@@ -95,6 +95,8 @@ void tselect_csr_write(CPURISCVState *env, target_ulong val);
 target_ulong tdata_csr_read(CPURISCVState *env, int tdata_index);
 void tdata_csr_write(CPURISCVState *env, int tdata_index, target_ulong val);
 
+target_ulong tinfo_csr_read(CPURISCVState *env);
+
 void riscv_cpu_debug_excp_handler(CPUState *cs);
 bool riscv_cpu_debug_check_breakpoint(CPUState *cs);
 bool riscv_cpu_debug_check_watchpoint(CPUState *cs, CPUWatchpoint *wp);