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From:   Jerry Shih <jerry.shih@sifive.com>
To:     paul.walmsley@sifive.com, palmer@dabbelt.com,
        aou@eecs.berkeley.edu, herbert@gondor.apana.org.au,
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        linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
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Subject: [PATCH 01/12] RISC-V: add helper function to read the vector VLEN
Date:   Thu, 26 Oct 2023 02:36:33 +0800
Message-Id: <20231025183644.8735-2-jerry.shih@sifive.com>
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From: Heiko Stuebner <heiko.stuebner@vrull.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@vrull.eu>
Signed-off-by: Jerry Shih <jerry.shih@sifive.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 9fb2dea66abd..1fd3e5510b64 100644
--- a/arch/riscv/include/asm/vector.h
+++ b/arch/riscv/include/asm/vector.h
@@ -244,4 +244,15 @@ void kernel_vector_allow_preemption(void);
 #define kernel_vector_allow_preemption()	do {} while (0)
 #endif
 
+/*
+ * 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