[PATCH RFC 05/20] RISC-V: Define indirect CSR access helpers

[Atish Patra <atishp@rivosinc.com>]

The indriect CSR requires multiple instructions to read/write CSR.
Add a few helper functions for ease of usage.

Signed-off-by: Atish Patra <atishp@rivosinc.com>
---
 arch/riscv/include/asm/csr_ind.h | 42 ++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)
 create mode 100644 arch/riscv/include/asm/csr_ind.h

diff --git a/arch/riscv/include/asm/csr_ind.h b/arch/riscv/include/asm/csr_ind.h
new file mode 100644
index 000000000000..9611c221eb6f
--- /dev/null
+++ b/arch/riscv/include/asm/csr_ind.h
@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2024 Rivos Inc.
+ */
+
+#ifndef _ASM_RISCV_CSR_IND_H
+#define _ASM_RISCV_CSR_IND_H
+
+#include <asm/csr.h>
+
+#define csr_ind_read(iregcsr, iselbase, iseloff) ({	\
+	unsigned long value = 0;			\
+	unsigned long flags;				\
+	local_irq_save(flags);				\
+	csr_write(CSR_ISELECT, iselbase + iseloff);	\
+	value = csr_read(iregcsr);			\
+	local_irq_restore(flags);			\
+	value;						\
+})
+
+#define csr_ind_write(iregcsr, iselbase, iseloff, value) ({	\
+	unsigned long flags;					\
+	local_irq_save(flags);					\
+	csr_write(CSR_ISELECT, iselbase + iseloff);		\
+	csr_write(iregcsr, value);				\
+	local_irq_restore(flags);				\
+})
+
+#define csr_ind_warl(iregcsr, iselbase, iseloff, warl_val) ({	\
+	unsigned long old_val = 0, value = 0;			\
+	unsigned long flags;					\
+	local_irq_save(flags);					\
+	csr_write(CSR_ISELECT, iselbase + iseloff);		\
+	old_val = csr_read(iregcsr);				\
+	csr_write(iregcsr, value);				\
+	value = csr_read(iregcsr);				\
+	csr_write(iregcsr, old_val);				\
+	local_irq_restore(flags);				\
+	value;							\
+})
+
+#endif
-- 
2.34.1