lib: sbi: Detect Sscofpmf extension at run time

Sscofpmf ISA extension introduces PMU counter overflow and filtering support.
It introduces a read only `scountovf` csr that can be used to detect if
a hart supports this extension at runtime. However, this feature is only
useful if the hart already supports mcounteren and mcountinhibit.

Add a dynamic detection mechanism and boot time print message if sscofpmf
is present.

Reviewed-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.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 0c18ef9..d2db9d6 100644 (file)
--- a/include/sbi/sbi_hart.h
+++ b/include/sbi/sbi_hart.h
@@ -20,8 +20,10 @@ enum sbi_hart_features {
        SBI_HART_HAS_MCOUNTEREN = (1 << 1),
        /** Hart has counter inhibit CSR */
        SBI_HART_HAS_MCOUNTINHIBIT = (1 << 2),
+       /** Hart has sscofpmf extension */
+       SBI_HART_HAS_SSCOFPMF = (1 << 3),
        /** HART has timer csr implementation in hardware */
-       SBI_HART_HAS_TIME = (1 << 3),
+       SBI_HART_HAS_TIME = (1 << 4),
 
        /** 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 8eb0c38..7f31bb7 100644 (file)
--- a/lib/sbi/sbi_hart.c
+++ b/lib/sbi/sbi_hart.c
@@ -281,6 +281,9 @@ static inline char *sbi_hart_feature_id2string(unsigned long feature)
        case SBI_HART_HAS_MCOUNTINHIBIT:
                fstr = "mcountinhibit";
                break;
+       case SBI_HART_HAS_SSCOFPMF:
+               fstr = "sscofpmf";
+               break;
        case SBI_HART_HAS_TIME:
                fstr = "time";
                break;
@@ -490,6 +493,15 @@ __mhpm_skip:
                        hfeatures->features |= SBI_HART_HAS_MCOUNTINHIBIT;
        }
 
+       /* Counter overflow/filtering is not useful without mcounter/inhibit */
+       if (hfeatures->features & SBI_HART_HAS_MCOUNTINHIBIT &&
+           hfeatures->features & SBI_HART_HAS_MCOUNTEREN) {
+               /* Detect if hart supports sscofpmf */
+               csr_read_allowed(CSR_SCOUNTOVF, (unsigned long)&trap);
+               if (!trap.cause)
+                       hfeatures->features |= SBI_HART_HAS_SSCOFPMF;
+       }
+
        /* Detect if hart supports time CSR */
        csr_read_allowed(CSR_TIME, (unsigned long)&trap);
        if (!trap.cause)