RISC-V: Add cpu_ops and modify default booting method

Currently, all non-booting harts start booting after the booting hart
updates the per-hart stack pointer. This is done in a way that, it's
difficult to implement any other booting method without breaking the
backward compatibility.

Define a cpu_ops method that allows to introduce other booting methods
in future. Modify the current booting method to be compatible with
cpu_ops.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

1 files changed, 34 insertions, 0 deletions

diff --git a/arch/riscv/include/asm/cpu_ops.h b/arch/riscv/include/asm/cpu_ops.h
new file mode 100644
index 000000000000..5ce81a28e1d9
--- /dev/null
+++ b/arch/riscv/include/asm/cpu_ops.h
@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2020 Western Digital Corporation or its affiliates.
+ * Based on arch/arm64/include/asm/cpu_ops.h
+ */
+#ifndef __ASM_CPU_OPS_H
+#define __ASM_CPU_OPS_H
+
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/threads.h>
+
+/**
+ * struct cpu_operations - Callback operations for hotplugging CPUs.
+ *
+ * @name:		Name of the boot protocol.
+ * @cpu_prepare:	Early one-time preparation step for a cpu. If there
+ *			is a mechanism for doing so, tests whether it is
+ *			possible to boot the given HART.
+ * @cpu_start:		Boots a cpu into the kernel.
+ */
+struct cpu_operations {
+	const char	*name;
+	int		(*cpu_prepare)(unsigned int cpu);
+	int		(*cpu_start)(unsigned int cpu,
+				     struct task_struct *tidle);
+};
+
+extern const struct cpu_operations *cpu_ops[NR_CPUS];
+void __init cpu_set_ops(int cpu);
+void cpu_update_secondary_bootdata(unsigned int cpuid,
+				   struct task_struct *tidle);
+
+#endif /* ifndef __ASM_CPU_OPS_H */