[PATCH v2 2/3] lib: sbi: Detect Smstateen CSRs at boot-time

[Mayuresh Chitale]

Extend HART feature detection to discover Smstateen CSRs at boot-time
and configure mstateen envcfg bit depending on availability of
menvcfg CSR.

Signed-off-by: Mayuresh Chitale <mchitale at ventanamicro.com>
---
 include/sbi/sbi_hart.h |  4 +++-
 lib/sbi/sbi_hart.c     | 25 +++++++++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/include/sbi/sbi_hart.h b/include/sbi/sbi_hart.h
index 57f80bc..be3ad9f 100644
--- a/include/sbi/sbi_hart.h
+++ b/include/sbi/sbi_hart.h
@@ -28,9 +28,11 @@ enum sbi_hart_features {
 	SBI_HART_HAS_AIA = (1 << 5),
 	/** HART has menvcfg CSR */
 	SBI_HART_HAS_MENVCFG = (1 << 6),
+	/** HART has mstateen CSR **/
+	SBI_HART_HAS_SMSTATEEN = (1 << 7),
 
 	/** Last index of Hart features*/
-	SBI_HART_HAS_LAST_FEATURE = SBI_HART_HAS_MENVCFG,
+	SBI_HART_HAS_LAST_FEATURE = SBI_HART_HAS_SMSTATEEN,
 };
 
 struct sbi_scratch;
diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
index 6be9286..db08eaf 100644
--- a/lib/sbi/sbi_hart.c
+++ b/lib/sbi/sbi_hart.c
@@ -43,6 +43,7 @@ static void mstatus_init(struct sbi_scratch *scratch)
 	int cidx;
 	unsigned int num_mhpm = sbi_hart_mhpm_count(scratch);
 	uint64_t mhpmevent_init_val = 0;
+	unsigned long mstateen_val;
 
 	/* Enable FPU */
 	if (misa_extension('D') || misa_extension('F'))
@@ -87,6 +88,22 @@ static void mstatus_init(struct sbi_scratch *scratch)
 #endif
 	}
 
+	if (sbi_hart_has_feature(scratch, SBI_HART_HAS_SMSTATEEN)) {
+		mstateen_val = csr_read(CSR_MSTATEEN0);
+#if __riscv_xlen == 32
+		mstateen_val |= ((uint64_t)csr_read(CSR_MSTATEEN0H)) << 32;
+#endif
+		mstateen_val |= SMSTATEEN_STATEN;
+		if (sbi_hart_has_feature(scratch, SBI_HART_HAS_MENVCFG))
+			mstateen_val |= SMSTATEEN0_HSENVCFG;
+		else
+			mstateen_val &= ~SMSTATEEN0_HSENVCFG;
+		csr_write(CSR_MSTATEEN0, mstateen_val);
+#if __riscv_xlen == 32
+		csr_write(CSR_MSTATEEN0H, mstateen_val >> 32);
+#endif
+	}
+
 	if (sbi_hart_has_feature(scratch, SBI_HART_HAS_MENVCFG)) {
 		menvcfg_val = csr_read(CSR_MENVCFG);
 
@@ -348,6 +365,9 @@ static inline char *sbi_hart_feature_id2string(unsigned long feature)
 	case SBI_HART_HAS_MENVCFG:
 		fstr = "menvcfg";
 		break;
+	case SBI_HART_HAS_SMSTATEEN:
+		fstr = "smstateen";
+		break;
 	default:
 		break;
 	}
@@ -584,6 +604,11 @@ __aia_skip:
 	if (!trap.cause)
 		hfeatures->features |= SBI_HART_HAS_MENVCFG;
 
+	/* Detect if hart supports mstateen CSRs */
+	val = csr_read_allowed(CSR_MSTATEEN0, (unsigned long)&trap);
+	if (!trap.cause)
+		hfeatures->features |= SBI_HART_HAS_SMSTATEEN;
+
 	return;
 }
 
-- 
2.17.1