System Control
ARM DDI 0500D
Copyright © 2013-2014 ARM. All rights reserved.
4-68
ID021414
Non-Confidential
Table 4-73 MDCR_EL2 bit assignments
Bits
Name
Function
[31:12]
-
Reserved,
RES
0.
[11]
TDRA
Trap debug ROM address register access.
0
Has no effect on accesses to debug ROM address registers from EL1 and EL0.
1
Trap valid Non-secure EL1 and EL0 access to debug ROM address registers to Hyp mode.
When this bit is set to 1, any access to the following registers from EL1 or EL0 is trapped to EL2:
•
AArch32: DBGDRAR, DBGDSAR.
•
AArch64: MDRAR_EL1.
If HCR_EL2.TGE is 1 or MDCR_EL2.TDE is 1, then this bit is ignored and treated as though it is 1 other than
for the value read back from MDCR_EL2.
On Warm reset, the field resets to 0.
[10]
TDOSA
Trap Debug OS-related register access:
0
Has no effect on accesses to OS-related debug registers.
1
Trap valid Non-secure accesses to OS-related debug registers to EL2.
When this bit is set to 1, any access to the following registers from EL1 or EL0 is trapped to EL2:
•
AArch32: DBGOSLAR, DBGOSLSR, DBGOSDLR, DBGPRCR.
•
AArch64: OSLAR_EL1, OSLSR_EL1, OSDLR_EL1, DBGPRCR_EL1.
If HCR_EL2.TGE is 1 or MDCR_EL2.TDE is 1, then this bit is ignored and treated as though it is 1 other than
for the value read back from MDCR_EL2.
On Warm reset, the field resets to 0.
[9]
TDA
Trap Debug Access:
0
Has no effect on accesses to Debug registers.
1
Trap valid Non-secure accesses to Debug registers to EL2.
When this bit is set to 1, any valid Non-secure access to the debug registers from EL1 or EL0, other than the
registers trapped by the TDRA and TDOSA bits, is trapped to EL2.
If HCR_EL2.TGE is 1 or MDCR_EL2.TDE is1, then this bit is ignored and treated as though it is 1 other than
for the value read back from MDCR_EL2.
On Warm reset, the field resets to 0.
[8]
TDE
Trap software debug exceptions:
0
Has no effect on software debug exceptions.
1
Route Software debug exceptions from Non-secure EL1 and EL0 to EL2. Also enables traps on
all debug register accesses to EL2.
If HCR_EL2.TGE is 1, then this bit is ignored and treated as though it is 1 other than for the value read back
from MDCR_EL2.This bit resets to 0.
[7]
HPME
Hypervisor Performance Monitor Enable:
0
EL2 performance monitor counters disabled.
1
EL2 performance monitor counters enabled.
When this bit is set to 1, the Performance Monitors counters that are reserved for use from EL2 or Secure state
are enabled. For more information see the description of the HPMN field.
The reset value of this bit is
UNKNOWN
.
[6]
TPM
Trap Performance Monitor accesses:
0
Has no effect on performance monitor accesses.
1
Trap Non-secure EL0 and EL1 accesses to Performance Monitors registers that are not
UNALLOCATED
to EL2.
This bit resets to 0.