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>

diff --git a/include/sbi/sbi_hart.h b/include/sbi/sbi_hart.h
index 031c7b0..9e317c5 100644 (file)
--- 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 (file)
--- 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)