[PATCH] lib: sbi: Add Smrnmi extension detection

[Nylon Chen]

The commit adds detection and initialization of the Smrnmi
extension in the SBI hart initialization code.

If the extension is detected,
it sets the NMIE bit in the mnstatus CSR to enable RNMIs out of reset.

Co-developed-by: Zong Li <zong.li at sifive.com>
Signed-off-by: Zong Li <zong.li at sifive.com>
Signed-off-by: Nylon Chen <nylon.chen at sifive.com>
Signed-off-by: Yong-Xuan Wang <yongxuan.wang at sifive.com>
---
 include/sbi/riscv_encoding.h | 10 ++++++++++
 include/sbi/sbi_hart.h       |  2 ++
 lib/sbi/sbi_hart.c           |  6 ++++++
 3 files changed, 18 insertions(+)

diff --git a/include/sbi/riscv_encoding.h b/include/sbi/riscv_encoding.h
index 2082783..93228ce 100644
--- a/include/sbi/riscv_encoding.h
+++ b/include/sbi/riscv_encoding.h
@@ -215,6 +215,10 @@
 
 #endif
 
+#define MNSTATUS_NMIE			(_UL(0x8))
+#define MNSTATUS_MNPV			(_UL(0x80))
+#define MNSTATUS_MNPP			(_UL(0x1800))
+
 #define MHPMEVENT_SSCOF_MASK		_ULL(0xFF00000000000000)
 
 #define ENVCFG_STCE			(_ULL(1) << 63)
@@ -770,6 +774,12 @@
 #define CSR_MSTATEEN3			0x30F
 #define CSR_MSTATEEN3H			0x31F
 
+/* Smrnmi extension registers */
+#define CSR_MNSCRATCH			0x740
+#define CSR_MNEPC			0x741
+#define CSR_MNCAUSE			0x742
+#define CSR_MNSTATUS			0x744
+
 /* Machine-Level High-Half CSRs (AIA) */
 #define CSR_MIDELEGH			0x313
 #define CSR_MIEH			0x314
diff --git a/include/sbi/sbi_hart.h b/include/sbi/sbi_hart.h
index c3a7feb..07cbead 100644
--- a/include/sbi/sbi_hart.h
+++ b/include/sbi/sbi_hart.h
@@ -79,6 +79,8 @@ enum sbi_hart_extensions {
 	SBI_HART_EXT_SMCTR,
 	/** HART has CTR S-mode CSRs */
 	SBI_HART_EXT_SSCTR,
+	/** HART has Smrnmi extension */
+	SBI_HART_EXT_SMRNMI,
 
 	/** Maximum index of Hart extension */
 	SBI_HART_EXT_MAX,
diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
index eefb03f..66d5d02 100644
--- a/lib/sbi/sbi_hart.c
+++ b/lib/sbi/sbi_hart.c
@@ -65,6 +65,11 @@ static void mstatus_init(struct sbi_scratch *scratch)
 	/* All programmable counters will start running at runtime after S-mode request */
 	if (sbi_hart_priv_version(scratch) >= SBI_HART_PRIV_VER_1_11)
 		csr_write(CSR_MCOUNTINHIBIT, 0xFFFFFFF8);
+	/* Detect Resumable Non-Maskable Interrupts
+	 * If it exists we must enable it before all traps.
+	 */
+	if (sbi_hart_has_extension(scratch, SBI_HART_EXT_SMRNMI))
+		csr_set(CSR_MNSTATUS, MNSTATUS_NMIE);
 
 	/**
 	 * The mhpmeventn[h] CSR should be initialized with interrupt disabled
@@ -695,6 +700,7 @@ const struct sbi_hart_ext_data sbi_hart_ext[] = {
 	__SBI_HART_EXT_DATA(ssdbltrp, SBI_HART_EXT_SSDBLTRP),
 	__SBI_HART_EXT_DATA(smctr, SBI_HART_EXT_SMCTR),
 	__SBI_HART_EXT_DATA(ssctr, SBI_HART_EXT_SSCTR),
+	__SBI_HART_EXT_DATA(smrnmi, SBI_HART_EXT_SMRNMI),
 };
 
 _Static_assert(SBI_HART_EXT_MAX == array_size(sbi_hart_ext),
-- 
2.39.3