arch: riscv: Add support for custom IPI implementation

Allow RISCV implementation to define its own custom IPI
implementation (e.g. Andes usage of PLIC for IPI)

Signed-off-by: Maxim Adelman <[email protected]>

Update arch/riscv/core/smp.c

Co-authored-by: Yong Cong Sin <[email protected]>

arch/riscv/Kconfig

@@ -112,6 +112,16 @@ config RISCV_SOC_HAS_CUSTOM_SYS_IO
 	  the RISC-V SoC needs to do something different and more than reading and
 	  writing the registers.
 
+config RISCV_SOC_HAS_CUSTOM_SMP_IPI
+	bool
+	select SCHED_IPI_SUPPORTED
+	help
+	  Hidden option to allow SoC to overwrite SMP IPI implementation
+	  Enable this hidden option and do the following:
+	  - implement arch_smp_init() which registers a custom SW IRQ handler
+	  - implement arch_sched_directed_ipi()
+	  - implement arch_flush_fpu_ipi()
+
 config RISCV_SOC_CONTEXT_SAVE
 	bool "SOC-based context saving in IRQ handlers"
 	select RISCV_SOC_OFFSETS

arch/riscv/core/smp.c

@@ -10,8 +10,10 @@
 #include <ipi.h>
 #include <zephyr/irq.h>
 #include <zephyr/sys/atomic.h>
+#include <zephyr/arch/arch_interface.h>
 #include <zephyr/arch/riscv/irq.h>
 #include <zephyr/drivers/pm_cpu_ops.h>
+#include <zephyr/platform/hooks.h>
 
 volatile struct {
 	arch_cpustart_t fn;
@@ -74,12 +76,17 @@ void arch_secondary_cpu_init(int hartid)
 #endif
 #ifdef CONFIG_SMP
 	irq_enable(RISCV_IRQ_MSOFT);
+#endif
+#ifdef CONFIG_SOC_SMP_PER_CORE_INIT_HOOK
+	soc_smp_per_core_init_hook();
 #endif
 	riscv_cpu_init[cpu_num].fn(riscv_cpu_init[cpu_num].arg);
 }
 
 #ifdef CONFIG_SMP
 
+#ifndef CONFIG_RISCV_SOC_HAS_CUSTOM_SMP_IPI
+
 #define MSIP_BASE 0x2000000UL
 #define MSIP(hartid) ((volatile uint32_t *)MSIP_BASE)[hartid]
 
@@ -104,11 +111,6 @@ void arch_sched_directed_ipi(uint32_t cpu_bitmap)
 	arch_irq_unlock(key);
 }
 
-void arch_sched_broadcast_ipi(void)
-{
-	arch_sched_directed_ipi(IPI_ALL_CPUS_MASK);
-}
-
 #ifdef CONFIG_FPU_SHARING
 void arch_flush_fpu_ipi(unsigned int cpu)
 {
@@ -172,4 +174,11 @@ int arch_smp_init(void)
 
 	return 0;
 }
+
+#endif /* CONFIG_RISCV_SOC_HAS_CUSTOM_SMP_IPI */
+
+void arch_sched_broadcast_ipi(void)
+{
+	arch_sched_directed_ipi(IPI_ALL_CPUS_MASK);
+}
 #endif /* CONFIG_SMP */

include/zephyr/platform/hooks.h

@@ -53,6 +53,14 @@ void soc_early_init_hook(void);
  */
 void soc_late_init_hook(void);
 
+/**
+ * @brief SoC per-core initialization during SMP bringup
+ *
+ * This hook is implemented by the SoC and can be used to perform any
+ * SoC-specific per-core initialization during SMP bringup
+ */
+void soc_smp_per_core_init_hook(void);
+
 /*
  * @brief Board hook executed before the kernel starts.
  *

kernel/Kconfig.init

@@ -32,6 +32,11 @@ config SOC_LATE_INIT_HOOK
 	help
 	  Run a late SoC initialization hook.
 
+config SOC_SMP_PER_CORE_INIT_HOOK
+	bool "Per-core initialization during SMP SoC hook"
+	help
+	  Per-core initialization during SMP SoC hook
+
 config BOARD_EARLY_INIT_HOOK
 	bool "Run early board hook"
 	help