Linux命令行如何实现休眠、关机功能？

OK3399-C平台采用RK3399 主CPU芯片设计，支持底板Power按键休眠唤醒以及关机功能，Linux命令行也可以通过命令进行关机，下面对这两种方式进行简单的解析。



Power按键


Power按键的休眠唤醒功能一般是与PMIC芯片和CPU相关的，硬件上该按键会连接到PMIC的PWRON引脚和CPU对应的引脚上。

先来看power按键在PMIC侧的响应机制，POWER键按下以后，经过TdbPWRONF时间以后，INT引脚变为低电平，触发中断。内核驱动响应中断，执行休眠程序。

如果PWRON继续保持低电平超过TdPWRONLP，PMIC就会响应，RK3399板卡将进行关机。



短按休眠和长按关机


Log信息：

[   10.250531] PM: Syncing filesystems ... done.
[   10.255148] test message.            //加入的测试信息
[   10.256842] Freezing user space processes ... (elapsed 0.003 seconds) done.
[   10.260770] Freezing remaining freezable tasks ... (elapsed 0.001 seconds) done.
[   10.263308] Suspending console(s) (use no_console_suspend to debug)
INFO:    sleep mode config[0xde]:
INFO:           AP_PWROFF
INFO:           SLP_ARMPD
INFO:           SLP_PLLPD
INFO:           DDR_RET
INFO:           SLP_CENTER_PD
INFO:    wakeup source config[0x804]:
INFO:           GPIO interrupt can wakeup system
INFO:           PWM interrupt can wakeup system
INFO:    PWM CONFIG[0x4]:
INFO:           PWM: PWM2D_REGULATOR_EN
INFO:    APIOS info[0x0]:
INFO:           not config
INFO:    GPIO POWER INFO:
INFO:           GPIO1_C1
INFO:           GPIO1_B6
INFO:    PMU_MODE_CONG: 0x1477bf51
涉及驱动文件

kernel/kernel/power/suspend.c
/**
* enter_state - Do common work needed to enter system sleep state.
* @state: System sleep state to enter.
*
* Make sure that no one else is trying to put the system into a sleep state.
* Fail if that's not the case.  Otherwise, prepare for system suspend, make the
* system enter the given sleep state and clean up after wakeup.
*/
static int enter_state(suspend_state_t state)
{
        int error;
        trace_suspend_resume(TPS("suspend_enter"), state, true);
        if (state == PM_SUSPEND_FREEZE) {
#ifdef CONFIG_PM_DEBUG
                if (pm_test_level != TEST_NONE && pm_test_level <= TEST_CPUS) {
                        pr_warning("PM: Unsupported test mode for suspend to idle,"
                                   "please choose none/freezer/devices/platform.n");
                        return -EAGAIN;
                }
#endif
        } else if (!valid_state(state)) {
                return -EINVAL;
        }
        if (!mutex_trylock(&pm_mutex))
                return -EBUSY;
        if (state == PM_SUSPEND_FREEZE)
                freeze_begin();
#ifndef CONFIG_SUSPEND_SKIP_SYNC
        trace_suspend_resume(TPS("sync_filesystems"), 0, true);
        printk(KERN_INFO "PM: Syncing filesystems ... ");
        sys_sync();
        printk("done.n");
        trace_suspend_resume(TPS("sync_filesystems"), 0, false);
#endif
        pr_debug("PM: Preparing system for sleep (%s)n", pm_states[state]);
        pm_suspend_clear_flags();
        error = suspend_prepare(state);
        if (error)
                goto Unlock;
        if (suspend_test(TEST_FREEZER))
                goto Finish;
        trace_suspend_resume(TPS("suspend_enter"), state, false);
        pr_debug("PM: Suspending system (%s)n", pm_states[state]);
        pm_restrict_gfp_mask();
        error = suspend_devices_and_enter(state);
        pm_restore_gfp_mask();
Finish:
        pr_debug("PM: Finishing wakeup.n");
        suspend_finish();
Unlock:
        mutex_unlock(&pm_mutex);
        return error;
}

通过代码可知，Power按键触发的休眠和关机会执行sys_sync函数，进行系统数据的保存，这与突然掉电导致的异常关机是有很大区别的。

关机命令


RK3399 平台Linux下的关机命令有shutdown、halt、poweroff命令等.

Poweroff命令关机


Log信息：

[root@rk3399:/]# poweroff
[root@rk3399:/]# stop finishedStopping input-event-daemon: done
stop auto-reboot finished
Stopping dnsmasq: OK
Stopping vsftpd: stopped vsftpd (pid 1072)
OK
[   20.099392] [BT_RFKILL]: bt shut off power
[   20.132245] configfs-gadget gadget: unbind function 'Function FS Gadget'/ffffffc07b025a38
Stopping sshd: OK
Stopping lighttpd: OK
Gracefully shutting down php-fpm . done
Stopping dhcpcd...
stopped /***in/dhcpcd (pid 924)
killall: rkisp_3A_server: no process killed
Stopping network: OK
stop finishedStopping system message bus: done
Saving random seed... done.
Stopping logging: OK
umount: can't remount adb read-only
umount: devtmpfs busy - remounted read-only
[   21.589884] EXT4-fs (mmcblk2p8): re-mounted. Opts: (null)
The system is going down NOW!
Sent SIGTERM to all processes
Sent SIGKILL to all processes
Requesting system poweroff
[   23.597578] cpu cpu4: min=816000, max=816000
[   23.598572] cpu cpu0: min=816000, max=816000
[   23.669985] I : [File] : drivers/gpu/arm/midgard_for_linux/platform/rk/mali_kbase_config_rk.c; [Line] : 274; [Func] : kbase_platform_rk_shutdown(); to make vdd_gpu enabled for turning off pd_gpu in pm_framework.
[   23.671701] rk-vcodec ff660000.rkvdec: shutdown
[   23.672132] rk-vcodec ff650000.vpu_service: shutdown
[   23.673046] rk808 0-001b: System power off
[   23.673419] rk808 0-001b: test message        //加入的测试信息

[root@rk3399:/]# poweroff --help
BusyBox v1.27.2 (2020-03-19 09:39:13 UTC) multi-call binary.
Usage: poweroff [-d DELAY] [-n] [-f]
Halt and shut off power
        -d SEC  Delay interval
        -n      Do not sync
        -f      Force (don't go through init)

Poweroff命令做的事可以从打印信息上看出来，其实可以分为两部分，一是配置系统，停止当前的服务，进行数据保存。二是调用电源管理驱动对应的接口，完成电源配置，RK3399 主板进行关机。

涉及驱动文件

kernel/drivers/mfd/rk808.c
static void rk808_syscore_shutdown(void)
{
        int ret;
        struct rk808 *rk808 = i2c_get_clientdata(rk808_i2c_client);
        if (!rk808) {
                dev_warn(&rk808_i2c_client->dev,
                         "have no rk808, so do nothing heren");
                return;
        }
        /* close rtc int when power off */
        regmap_update_bits(rk808->regmap,
                           RK808_INT_STS_MSK_REG1,
                           (0x3 << 5), (0x3 << 5));
        regmap_update_bits(rk808->regmap,
                           RK808_RTC_INT_REG,
                           (0x3 << 2), (0x0 << 2));
        /*
         * For PMIC that power off supplies by write register via i2c bus,
         * it's better to do power off at syscore shutdown here.
         *
         * Because when run to kernel's "pm_power_off" call, i2c may has
         * been stopped or PMIC may not be able to get i2c transfer while
         * there are too many devices are competiting.
         */
         if (system_state == SYSTEM_POWER_OFF) {
                /* power off supplies ! */
                if (pm_shutdown) {
                        dev_info(&rk808_i2c_client->dev, "System power offn");
                        ret = pm_shutdown(rk808->regmap);
                        if (ret)
                                dev_err(&rk808_i2c_client->dev,
                                        "System power off error!n");
                        mdelay(10);
                        dev_info(&rk808_i2c_client->dev,
                                 "Cpu should never reach here, stop!n");
                        while (1)
                                ;
                }
        }
}
#define DEV_OFF_RST     BIT(3)
static int rk808_shutdown(struct regmap *regmap)
{
        int ret;
        ret = regmap_update_bits(regmap,
                                 RK808_DEVCTRL_REG,
                                 DEV_OFF_RST, DEV_OFF_RST);
        return ret;
}
  


最终调用的的rk808shutdown接口函数，对RK808DEVCTRLREG寄存器写入DEVOFF_RST，触发RK3399主板关机。