linux-kernel - [PATCH v5 3/7] riscv: Add xmipsexectl instructions

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Message-Id: <20250724-p8700-pause-v5-3-a6cbbe1c3412@htecgroup.com>
Date: Thu, 24 Jul 2025 17:23:27 +0200
From: Aleksa Paunovic via B4 Relay <devnull+aleksa.paunovic.htecgroup.com@...nel.org>
To: Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, 
 Paul Walmsley <paul.walmsley@...ive.com>, 
 Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
 Alexandre Ghiti <alex@...ti.fr>, Jonathan Corbet <corbet@....net>
Cc: Palmer Dabbelt <palmer@...ive.com>, Conor Dooley <conor@...nel.org>, 
 Djordje Todorovic <djordje.todorovic@...cgroup.com>, 
 devicetree@...r.kernel.org, linux-riscv@...ts.infradead.org, 
 linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org, 
 Aleksa Paunovic <aleksa.paunovic@...cgroup.com>, 
 Alexandre Ghiti <alexghiti@...osinc.com>
Subject: [PATCH v5 3/7] riscv: Add xmipsexectl instructions

From: Aleksa Paunovic <aleksa.paunovic@...cgroup.com>

Add xmipsexectl instruction opcodes. This includes the MIPS.PAUSE,
MIPS.EHB, and MIPS.IHB instructions.

Signed-off-by: Aleksa Paunovic <aleksa.paunovic@...cgroup.com>
Reviewed-by: Alexandre Ghiti <alexghiti@...osinc.com>
---
 arch/riscv/include/asm/vendor_extensions/mips.h | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/arch/riscv/include/asm/vendor_extensions/mips.h b/arch/riscv/include/asm/vendor_extensions/mips.h
index 133e55985d827ce7d6057004b590bdcbbdb1ec8c..ea8ca747d691df2e9ee7e5360f800fbdccfe3945 100644
--- a/arch/riscv/include/asm/vendor_extensions/mips.h
+++ b/arch/riscv/include/asm/vendor_extensions/mips.h
@@ -15,4 +15,23 @@ struct riscv_isa_vendor_ext_data_list;
 extern struct riscv_isa_vendor_ext_data_list riscv_isa_vendor_ext_list_mips;
 #endif
 
+/* Extension specific instructions */
+
+/*
+ * All of the xmipsexectl extension instructions are
+ * ‘hint’ encodings of the SLLI instruction,
+ * with rd = 0, rs1 = 0 and imm = 1 for IHB, imm = 3 for EHB,
+ * and imm = 5 for PAUSE.
+ * MIPS.PAUSE is an alternative opcode which is implemented to have the
+ * same behavior as PAUSE on some MIPS RISCV cores.
+ * MIPS.EHB clears all execution hazards before allowing
+ * any subsequent instructions to execute.
+ * MIPS.IHB clears all instruction hazards before
+ * allowing any subsequent instructions to fetch.
+ */
+
+#define MIPS_PAUSE	".4byte 0x00501013\n\t"
+#define MIPS_EHB	".4byte 0x00301013\n\t"
+#define MIPS_IHB	".4byte 0x00101013\n\t"
+
 #endif // _ASM_RISCV_VENDOR_EXTENSIONS_MIPS_H

-- 
2.34.1