[PATCH -next v13 04/19] riscv: Clear vector regfile on bootup

[Andy Chiu <andy.chiu@sifive.com>]

clear vector registers on boot if kernel supports V.

Signed-off-by: Greentime Hu <greentime.hu@sifive.com>
Signed-off-by: Vineet Gupta <vineetg@rivosinc.com>
[vineetg: broke this out to a seperate patch]
Signed-off-by: Andy Chiu <andy.chiu@sifive.com>
---
 arch/riscv/kernel/head.S | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index b865046e4dbb..ea803c96eeff 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -431,6 +431,29 @@ ENTRY(reset_regs)
 	csrw	fcsr, 0
 	/* note that the caller must clear SR_FS */
 #endif /* CONFIG_FPU */
+
+#ifdef CONFIG_RISCV_ISA_V
+	csrr	t0, CSR_MISA
+	li	t1, COMPAT_HWCAP_ISA_V
+	and	t0, t0, t1
+	beqz	t0, .Lreset_regs_done
+
+	/*
+	 * Clear vector registers and reset vcsr
+	 * VLMAX has a defined value, VLEN is a constant,
+	 * and this form of vsetvli is defined to set vl to VLMAX.
+	 */
+	li	t1, SR_VS
+	csrs	CSR_STATUS, t1
+	csrs	CSR_VCSR, x0
+	vsetvli t1, x0, e8, m8, ta, ma
+	vmv.v.i v0, 0
+	vmv.v.i v8, 0
+	vmv.v.i v16, 0
+	vmv.v.i v24, 0
+	/* note that the caller must clear SR_VS */
+#endif /* CONFIG_RISCV_ISA_V */
+
 .Lreset_regs_done:
 	ret
 END(reset_regs)
-- 
2.17.1