RISC-V: add helper function to read the vector VLEN

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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>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jerry Shih <jerry.shih@sifive.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20240122002024.27477-2-ebiggers@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

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Heiko Stuebner 2024-01-21 16:19:12 -08:00 • committed by Palmer Dabbelt

parent 6613476e22

commit df513ed49f

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arch/riscv/include/asm/vector.h

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