| PSCI | Power State Coordination Interface | 功耗状态协同接口 |
| SCPI | System Control and Power Interface | 系统控制和电源接口 |
| SCMI | System Control and Management Interface | 系统控制和管理接口 |
| SMCCC | SMC Calling Convention | SMC调用约定 |
scpi；通过mailbox核间通信，如风扇，温度。。。
psci：调用smc。如开关机，cpu停止启动
PSCI控制cpu的行为，比如关核等。。系统的关机和启动。cpu的热插拔。
系统reboot系统调用：
kernel/reboot.c
SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,void __user *, arg)
{switch (cmd) {case LINUX_REBOOT_CMD_RESTART:kernel_restart(NULL);break;case LINUX_REBOOT_CMD_RESTART2:ret = strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1);if (ret < 0) {ret = -EFAULT;break;}buffer[sizeof(buffer) - 1] = '\0';kernel_restart(buffer);break;....
#ifdef CONFIG_KEXEC_COREcase LINUX_REBOOT_CMD_KEXEC:ret = kernel_kexec();break;
#endif#ifdef CONFIG_HIBERNATIONcase LINUX_REBOOT_CMD_SW_SUSPEND:ret = hibernate();break;
#endif
}
重启/reset调用kernel_restart：
//kernel/reboot.c
kernel_restart:
void kernel_restart(char *cmd)
{kernel_restart_prepare(cmd);migrate_to_reboot_cpu();syscore_shutdown(); if (!cmd)pr_emerg("Restarting system\n");elsepr_emerg("Restarting system with command '%s'\n", cmd);kmsg_dump(KMSG_DUMP_SHUTDOWN);machine_restart(cmd); //arch/arm64/kernel/process.c
}//arch/arm64/kernel/process.c
void machine_restart(char *cmd)
{/* Disable interrupts first */local_irq_disable();smp_send_stop();/** UpdateCapsule() depends on the system being reset via* ResetSystem().*/if (efi_enabled(EFI_RUNTIME_SERVICES))efi_reboot(reboot_mode, NULL); //如果efi支持，则调用efi的runtime_services/* Now call the architecture specific reboot code. */if (arm_pm_restart)arm_pm_restart(reboot_mode, cmd); //如果arm_pm_restart存在，这个定义在drivers/firmware/psci/psci.celsedo_kernel_restart(cmd);/** Whoops - the architecture was unable to reboot.*/printk("Reboot failed -- System halted\n");while (1);
}休眠调用hinernate：
hibernate：power_downkernel_power_off()machine_power_offlocal_irq_disable();smp_send_stop();if (pm_power_off)pm_power_off(); //调用psci的函数psci_sys_poweroffkernel_halt();上面一个调用arm_pm_restart和pm_power_off两个函数指针都在drivers/firmware/psci/psci.c中实现，同时也实现了psci_ops相关的函数，用来对cpu的控制：
static void __init psci_0_2_set_functions(void)
{pr_info("Using standard PSCI v0.2 function IDs\n");psci_ops.get_version = psci_get_version;psci_function_id[PSCI_FN_CPU_SUSPEND] =PSCI_FN_NATIVE(0_2, CPU_SUSPEND);psci_ops.cpu_suspend = psci_cpu_suspend;psci_function_id[PSCI_FN_CPU_OFF] = PSCI_0_2_FN_CPU_OFF;psci_ops.cpu_off = psci_cpu_off;psci_function_id[PSCI_FN_CPU_ON] = PSCI_FN_NATIVE(0_2, CPU_ON);psci_ops.cpu_on = psci_cpu_on;psci_function_id[PSCI_FN_MIGRATE] = PSCI_FN_NATIVE(0_2, MIGRATE);psci_ops.migrate = psci_migrate;psci_ops.affinity_info = psci_affinity_info;psci_ops.migrate_info_type = psci_migrate_info_type;arm_pm_restart = psci_sys_reset;pm_power_off = psci_sys_poweroff;
}比如
static void psci_sys_poweroff(void){invoke_psci_fn(PSCI_0_2_FN_SYSTEM_OFF, 0, 0, 0);}
PSCI_0_2_FN_SYSTEM_OFF的值计算为：0x84000000+8,在规范的表6-2：分配给不同服务的功能标识符的子范围中：
相关定义在include/uapi/linux/psci.h
SCPI：
scpi是用来通过mailbox和其它核的通信，比如M核。
SoC就是System on Chip，一个芯片上集成了一个系统，一个系统往往有很多核，例如M核、A核、R核，以及异构的RISC-V核等，集成到一个芯片上的好处就是节省成本并且体积更小，能耗也更低，可谓是一举多得。但是多个核上的各种OS之间就需要进行通信，这也就是本文的主题：核间通信。核间通信也称为Mailbox，Mailbox技术是由软硬件协同实现的。
SoC软件技术--核间通信
TODO。比如风扇温度等。。
