You copied the Doc URL to your clipboard.

CNTPS_TVAL_EL1, Counter-timer Physical Secure Timer TimerValue register

The CNTPS_TVAL_EL1 characteristics are:

Purpose

Holds the timer value for the secure physical timer, usually accessible at EL3 but configurably accessible at EL1 in Secure state.

Configuration

RW fields in this register reset to architecturally UNKNOWN values.

Attributes

CNTPS_TVAL_EL1 is a 64-bit register.

Field descriptions

The CNTPS_TVAL_EL1 bit assignments are:

63	62	61	60	59	58	57	56	55	54	53	52	51	50	49	48	47	46	45	44	43	42	41	40	39	38	37	36	35	34	33	32
RES0
TimerValue
31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0

Bits [63:32]

Reserved, RES0.

TimerValue, bits [31:0]

The TimerValue view of the secure physical timer.

On a read of this register:

If CNTPS_CTL_EL1.ENABLE is 0, the value returned is UNKNOWN.
If CNTPS_CTL_EL1.ENABLE is 1, the value returned is (CNTPS_CVAL_EL1 - CNTPCT_EL0).

On a write of this register, CNTPS_CVAL_EL1 is set to (CNTPCT_EL0 + TimerValue), where TimerValue is treated as a signed 32-bit integer.

When CNTPS_CTL_EL1.ENABLE is 1, the timer condition is met when (CNTPCT_EL0 - CNTPS_CVAL_EL1) is greater than or equal to zero. This means that TimerValue acts like a 32-bit downcounter timer. When the timer condition is met:

CNTPS_CTL_EL1.ISTATUS is set to 1.
If CNTPS_CTL_EL1.IMASK is 0, an interrupt is generated.

When CNTPS_CTL_EL1.ENABLE is 0, the timer condition is not met, but CNTPCT_EL0 continues to count, so the TimerValue view appears to continue to count down.

This field resets to an architecturally UNKNOWN value.

Accessing the CNTPS_TVAL_EL1

Accesses to this register use the following encodings:

MRS <Xt>, CNTPS_TVAL_EL1

op0	op1	CRn	CRm	op2
0b11	0b111	0b1110	0b0010	0b000

if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if HaveEL(EL3) && SCR_EL3.NS == '0' then
        if SCR_EL3.EEL2 == '1' then
            UNDEFINED;
        elsif SCR_EL3.ST == '0' then
            AArch64.SystemAccessTrap(EL3, 0x18);
        else
            return CNTPS_TVAL_EL1;
    else
        UNDEFINED;
elsif PSTATE.EL == EL2 then
    UNDEFINED;
elsif PSTATE.EL == EL3 then
    return CNTPS_TVAL_EL1;

MSR CNTPS_TVAL_EL1, <Xt>

op0	op1	CRn	CRm	op2
0b11	0b111	0b1110	0b0010	0b000

if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if HaveEL(EL3) && SCR_EL3.NS == '0' then
        if SCR_EL3.EEL2 == '1' then
            UNDEFINED;
        elsif SCR_EL3.ST == '0' then
            AArch64.SystemAccessTrap(EL3, 0x18);
        else
            CNTPS_TVAL_EL1 = X[t];
    else
        UNDEFINED;
elsif PSTATE.EL == EL2 then
    UNDEFINED;
elsif PSTATE.EL == EL3 then
    CNTPS_TVAL_EL1 = X[t];

Previous Next

Was this page helpful? Yes No