[PATCH] lib: sbi: Detect support of entropy source

[Xiang W]

Detect if entropy source, Zkr extension, is supported
by the HART.

Signed-off-by: Xiang W <wxjstz at 126.com>
---
 include/sbi/riscv_encoding.h |  3 +++
 lib/sbi/sbi_hart.c           | 14 ++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/include/sbi/riscv_encoding.h b/include/sbi/riscv_encoding.h
index 40a854e3..8ca607c0 100644
--- a/include/sbi/riscv_encoding.h
+++ b/include/sbi/riscv_encoding.h
@@ -261,6 +261,9 @@
 #define CSR_FRM				0x002
 #define CSR_FCSR			0x003
 
+/* User entropy source */
+#define CSR_SEED			0x015
+
 /* User Counters/Timers */
 #define CSR_CYCLE			0xc00
 #define CSR_TIME			0xc01
diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
index 1b50f671..ee655375 100644
--- a/lib/sbi/sbi_hart.c
+++ b/lib/sbi/sbi_hart.c
@@ -983,6 +983,20 @@ __pmp_skip:
 
 #undef __check_ext_csr
 
+#define __check_ext_csr_w(__base_priv, __csr, __val, __ext)		\
+	if (hfeatures->priv_version >= __base_priv) {			\
+		csr_write_allowed(__csr, &trap, __val);			\
+		if (!trap.cause)					\
+			__sbi_hart_update_extension(hfeatures,		\
+						    __ext, true);	\
+	}
+
+	/* Detect if hart supports Zkr (entropy source) */
+	__check_ext_csr_w(SBI_HART_PRIV_VER_UNKNOWN,
+			CSR_SEED, 0, SBI_HART_EXT_ZKR);
+
+#undef __check_ext_csr_w
+
 #define __check_csr_existence(__csr, __csr_id)				\
 	csr_read_allowed(__csr, &trap);					\
 	if (!trap.cause)						\
-- 
2.47.3