soc: gd32: gd32vf103: keep the mcause.interrupt by SOC-specific context

For Nuclei ECLIC, the interrupt level (mintstatus.MIL) is restored from
the previous interrupt level (mcause.MPIL) only if mcause.interrupt is set.
This behavior is not defined in the RISC-V CLIC spec.
If an ISR causes a context switch and mcause.interrupt is not set in the
next context (e.g. the next context is yielded from ecall), interrupts will
be masked after MRET because the interrupt level is not restored.

Use SOC-specific context to set mcause.interrupt to ensure the interrupt
level is restored correctly.

Signed-off-by: Jimmy Zheng <jimmyzhe@andestech.com>

soc/gd/gd32/gd32vf103/CMakeLists.txt

@@ -3,6 +3,7 @@
 
 zephyr_sources(entry.S)
 zephyr_sources(soc.c)
+zephyr_sources(soc_irq.S)
 
 zephyr_include_directories(.)
 

soc/gd/gd32/gd32vf103/Kconfig

@@ -14,6 +14,7 @@ config SOC_SERIES_GD32VF103
 	select RISCV_ISA_EXT_ZIFENCEI
 	select RISCV_HAS_CLIC
 	select RISCV_SOC_HAS_GP_RELATIVE_ADDRESSING
+	select RISCV_SOC_CONTEXT_SAVE
 	select ATOMIC_OPERATIONS_C
 	select INCLUDE_RESET_VECTOR
 	select GD32_HAS_AFIO_PINMUX

soc/gd/gd32/gd32vf103/soc_context.h

@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) 2024 Andes Technology Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef SOC_RISCV_GD32_GD32VF103_SOC_CONTEXT_H
+#define SOC_RISCV_GD32_GD32VF103_SOC_CONTEXT_H
+
+#ifdef CONFIG_RISCV_SOC_CONTEXT_SAVE
+
+	#define SOC_ESF_MEMBERS
+
+	#define SOC_ESF_INIT
+
+#endif  /* CONFIG_RISCV_SOC_CONTEXT_SAVE */
+
+#endif  /* SOC_RISCV_GD32_GD32VF103_SOC_CONTEXT_H */

soc/gd/gd32/gd32vf103/soc_irq.S

@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2024 Andes Technology Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/offsets.h>
+#include <zephyr/toolchain.h>
+#include <zephyr/arch/riscv/irq.h>
+
+/* Exports */
+#ifdef CONFIG_RISCV_SOC_CONTEXT_SAVE
+GTEXT(__soc_save_context)
+GTEXT(__soc_restore_context)
+#endif
+
+#ifdef CONFIG_RISCV_SOC_CONTEXT_SAVE
+
+SECTION_FUNC(exception.other, __soc_save_context)
+
+	ret
+
+SECTION_FUNC(exception.other, __soc_restore_context)
+
+	/*
+	 * For Nuclei ECLIC, the interrupt level (mintstatus.MIL) is restored
+	 * from the previous interrupt level (mcause.MPIL) only if
+	 * mcause.interrupt is set when executing MRET.
+	 * Always set the next context's mcause.interrupt to ensure the
+	 * interrupt level is restored correctly after MRET.
+	 */
+	addi a0, a0, -__struct_arch_esf_soc_context_OFFSET
+	lw t0, __struct_arch_esf_mcause_OFFSET(a0)
+	li t1, 1 << RISCV_MCAUSE_IRQ_POS
+	or t0, t0, t1
+	sw t0, __struct_arch_esf_mcause_OFFSET(a0)
+
+	ret
+
+#endif /* CONFIG_RISCV_SOC_CONTEXT_SAVE */

soc/gd/gd32/gd32vf103/soc_offsets.h

@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) 2024 Andes Technology Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef SOC_RISCV_GD32_GD32VF103_SOC_OFFSETS_H_
+#define SOC_RISCV_GD32_GD32VF103_SOC_OFFSETS_H_
+
+#ifdef CONFIG_RISCV_SOC_OFFSETS
+
+	#define GEN_SOC_OFFSET_SYMS()
+
+#endif  /* CONFIG_RISCV_SOC_OFFSETS */
+
+#endif  /* SOC_RISCV_GD32_GD32VF103_SOC_OFFSETS_H_*/