From fde28fadc2603c7c7a4afa7c2e7b96cc7b11d2e2 Mon Sep 17 00:00:00 2001
From: Atish Patra <atish.patra@wdc.com>
Date: Sat, 10 Jul 2021 09:18:03 -0700
Subject: lib: sbi: Detect mcountinihibit support at runtime
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>
---
include/sbi/sbi_hart.h | 4 +++-
lib/sbi/sbi_hart.c | 11 +++++++++++
2 files changed, 14 insertions(+), 1 deletion(-)
diff --git a/include/sbi/sbi_hart.h b/include/sbi/sbi_hart.h
index 031c7b0..9e317c5 100644
--- a/include/sbi/sbi_hart.h
+++ b/include/sbi/sbi_hart.h
@@ -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,
diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
index 56878b4..0bd1db1 100644
--- a/lib/sbi/sbi_hart.c
+++ b/lib/sbi/sbi_hart.c
@@ -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)
--
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