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lib: sbi: Detect mcountinihibit support at runtime

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RISC-V ISA specification v1.11 defined mcountinhibit CSR that allows
software to stop any counter from incrementing. The SBI PMU extension
depends on this CSR support in hardware.

Define mcountinhibit as a hart specific feature and detect it at runtime.

Reviewed-by: Anup Patel <anup.patel@wdc.com>
Signed-off-by: Atish Patra <atish.patra@wdc.com>
This commit is contained in:
Atish Patra 2021-07-10 09:18:03 -07:00 • committed by Anup Patel
parent 3e8b31aca9
commit fde28fadc2
2 changed files with 14 additions and 1 deletions
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4
include/sbi/sbi_hart.h
View file

@ -18,8 +18,10 @@ enum sbi_hart_features {
SBI_HART_HAS_SCOUNTEREN = (1 << 0),
/** Hart has M-mode counter enable */
SBI_HART_HAS_MCOUNTEREN = (1 << 1),
/** Hart has counter inhibit CSR */
SBI_HART_HAS_MCOUNTINHIBIT = (1 << 2),
/** HART has timer csr implementation in hardware */
SBI_HART_HAS_TIME = (1 << 2),
SBI_HART_HAS_TIME = (1 << 3),
/** Last index of Hart features*/
SBI_HART_HAS_LAST_FEATURE = SBI_HART_HAS_TIME,

11
lib/sbi/sbi_hart.c
View file

@ -259,6 +259,9 @@ static inline char *sbi_hart_feature_id2string(unsigned long feature)
case SBI_HART_HAS_MCOUNTEREN:
fstr = "mcounteren";
break;
case SBI_HART_HAS_MCOUNTINHIBIT:
fstr = "mcountinhibit";
break;
case SBI_HART_HAS_TIME:
fstr = "time";
break;
@ -421,6 +424,14 @@ __mhpm_skip:
hfeatures->features |= SBI_HART_HAS_MCOUNTEREN;
}
/* Detect if hart supports MCOUNTINHIBIT feature */
val = csr_read_allowed(CSR_MCOUNTINHIBIT, (unsigned long)&trap);
if (!trap.cause) {
csr_write_allowed(CSR_MCOUNTINHIBIT, (unsigned long)&trap, val);
if (!trap.cause)
hfeatures->features |= SBI_HART_HAS_MCOUNTINHIBIT;
}
/* Detect if hart supports time CSR */
csr_read_allowed(CSR_TIME, (unsigned long)&trap);
if (!trap.cause)