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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>
Atish Patra 2 years ago
parent
commit
867c65360d
2 changed files with 15 additions and 1 deletions
  1. 3 1
      include/sbi/sbi_hart.h
  2. 12 0
      lib/sbi/sbi_hart.c

+ 3 - 1
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,

+ 12 - 0
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)