[v4,01/11] RISC-V: add helper function to read the vector VLEN

Commit Message

Jerry Shih Dec. 31, 2023, 3:27 p.m. UTC

From: Heiko Stuebner <[e-mail]>

VLEN describes the length of each vector register and some instructions
need specific minimal VLENs to work correctly.

The vector code already includes a variable riscv_v_vsize that contains
the value of "32 vector registers with vlenb length" that gets filled
during boot. vlenb is the value contained in the CSR_VLENB register and
the value represents "VLEN / 8".

So add riscv_vector_vlen() to return the actual VLEN value for in-kernel
users when they need to check the available VLEN.

Signed-off-by: Heiko Stuebner <[e-mail]>
Reviewed-by: Eric Biggers <[e-mail]>
Signed-off-by: Jerry Shih <[e-mail]>
---
 arch/riscv/include/asm/vector.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

Patch

diff --git a/arch/riscv/include/asm/vector.h b/arch/riscv/include/asm/vector.h
index d69844906d51..b04ee0a50315 100644
--- a/arch/riscv/include/asm/vector.h
+++ b/arch/riscv/include/asm/vector.h
@@ -294,4 +294,15 @@  static inline bool riscv_v_vstate_ctrl_user_allowed(void) { return false; }
 
 #endif /* CONFIG_RISCV_ISA_V */
 
+/*
+ * Return the implementation's vlen value.
+ *
+ * riscv_v_vsize contains the value of "32 vector registers with vlenb length"
+ * so rebuild the vlen value in bits from it.
+ */
+static inline int riscv_vector_vlen(void)
+{
+	return riscv_v_vsize / 32 * 8;
+}
+
 #endif /* ! __ASM_RISCV_VECTOR_H */