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

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Date: Sun, 31 Dec 2023 23:27:33 +0800
From: Jerry Shih <jerry.shih@...ive.com>
To: paul.walmsley@...ive.com,
	palmer@...belt.com,
	aou@...s.berkeley.edu,
	herbert@...dor.apana.org.au,
	davem@...emloft.net,
	conor.dooley@...rochip.com,
	ebiggers@...nel.org,
	ardb@...nel.org
Cc: heiko@...ech.de,
	phoebe.chen@...ive.com,
	hongrong.hsu@...ive.com,
	linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-crypto@...r.kernel.org
Subject: [PATCH v4 01/11] RISC-V: add helper function to read the vector VLEN

From: Heiko Stuebner <heiko.stuebner@...ll.eu>

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 <heiko.stuebner@...ll.eu>
Reviewed-by: Eric Biggers <ebiggers@...gle.com>
Signed-off-by: Jerry Shih <jerry.shih@...ive.com>
---
 arch/riscv/include/asm/vector.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

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 */
-- 
2.28.0