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一个Linux平台PM功能初探

2024-09-28 09:21:02 213人阅读

WatchDog

用户空间节点

/dev/watchdog

/sys/bus/platform/devices/zx29_ap_wdt.0

/sys/bus/platform/drivers/zx29_ap_wdt

时钟资源

arch/arm/mach-zx297520v3/include/mach/iomap.h

#define ZX_LSP_CRPM_BASE (ZX_LSP_BASE)

drivers/clk/zte/clk-zx297520v3.c

/**************************************************************************
*   ap wdt
***************************************************************************
*/
char* lsp_wdt_wclk_parents[2] =
{
    NAME_CLK(main_clk_32k),
    NAME_CLK(main_clk_26m)
};

static struct zx29_hwclk ap_wdt_apb =
{
    .clk_en_reg     ={ZX_LSP_CRPM_BASE+0x40,    0,    1},
    .clk_div_reg    ={ZX_LSP_CRPM_BASE+0x40,    0,    0},
    .clk_gate_reg    ={ZX_LSP_CRPM_BASE+0x40,     11,    1},
};
DEFINE_ZX29_CLK(ap_wdt_apb,peripheral_clk_ops,0,NULL);

static struct zx29_hwclk ap_wdt_work =
{
    .clk_en_reg     ={ZX_LSP_CRPM_BASE+0x40,    1,    1},
    .clk_sel_reg    ={ZX_LSP_CRPM_BASE+0x40,    4,    1},
    .clk_div_reg    ={ZX_LSP_CRPM_BASE+0x40,    12,    4},
    .clk_gate_reg    ={ZX_LSP_CRPM_BASE+0x40,     10,    1},
};
DEFINE_ZX29_CLK(ap_wdt_work,peripheral_clk_ops,2,lsp_wdt_wclk_parents);

struct clk_lookup periph_clocks_lookups[] = {
    /*              dev_id       name                   clk struct */
…
    CLK_ZX29_CONFIG("zx29_ap_wdt.0", "work_clk",         &ap_wdt_work_clk), 表示设备名称zx29_ap_wdt.0下的work_clk
    CLK_ZX29_CONFIG("zx29_ap_wdt.0", "apb_clk",          &ap_wdt_apb_clk),
…

};

platform设备代码

中：

arch/arm/mach-zx297520v3/include/mach/iomap.h

#define ZX_AP_WDT_BASE (ZX_LSP_BASE + 0xE000)

arch/arm/mach-zx297520v3/zx297520v3-devices.c (这其中的资源会在probe中使用到)

static struct resource wdt_res[] = {
    [0] = {
        .start    = (u32)ZX_AP_WDT_BASE,
        .end    = (u32)ZX_AP_WDT_BASE + SZ_4K - 1,
        .flags = IORESOURCE_MEM,
    },
    [1] = {
        .start = WDT_INT,
        .end   = WDT_INT,
        .flags = IORESOURCE_IRQ,
    },
};

static struct platform_device zx297520v2_wdt_device = {
    .name = "zx29_ap_wdt",
    .id = 0,
    .resource = wdt_res,
    .num_resources    = ARRAY_SIZE(wdt_res),
};

struct platform_device *zx29_device_table[] __initdata=http://www.mamicode.com/{
/* --------------------------------------------------------------------
* ---------- for solution integration department --------- start
* -------------------------------------------------------------------- */
…
#ifdef CONFIG_ZX29_WATCHDOG
&zx297520v2_wdt_device,
#endif

…
}

platform驱动代码

drivers/watchdog/zx29_wdt.c中：

时钟相关

watchdog_init->platform_driver_register(&zx29_wdt_driver)-|->zx29_wdt_probe
                                                                                               -|->__devexit_p(zx29_wdt_remove)
                                                                                               -|->zx29_wdt_shutdown
                                                                                               -|->zx29_wdt_suspend
                                                                                               -|->zx29_wdt_resume
watchdog_exit->platform_driver_unregister(&zx29_wdt_driver)

cpuidle

menuconfig

CONFIG_CPU_IDLE=y
CONFIG_CPU_IDLE_GOV_LADDER=y
CONFIG_CPU_IDLE_GOV_MENU=y

cpuidle driver

在本平台中cpuidle driver没有作为单一的模块，二是放在zx_pm_init中进行。

drivers/soc/zte/power/zx-cpuidle.c

zx_pm_init-|->pm_debug_init->idle_debug_init (/sys/zte_pm/cpuidle/)
|->zx_cpuidle_init->

drivers/soc/zte/power/zx297520v3-cpuidle.c中定义了cpuidle的状态

#define WHOLE_CHIP_EXIT_LATENCY (4000) /* us */

#define LP2_DEFAULT_EXIT_LATENCY (500 + WHOLE_CHIP_EXIT_LATENCY) /* us */
#define LP2_MIN_POWER_OFF_TIME (500) /* us */

#define LP2_DELTA_EXIT_LATENCY (100) /* us -- for timer setting refresh time, should > 2us.

static struct cpuidle_state zx297520v3_cpuidle_set[] __initdata =http://www.mamicode.com/
{
    /* LP3 -- wfi */
    [ZX_IDLE_CSTATE_LP3] =
    {
        .enter                = zx_enter_idle,
        .exit_latency        = 2,
        .target_residency    = 5,
        .flags                = CPUIDLE_FLAG_TIME_VALID,
        .name                = "LP3",
        .desc                = "clock gating(WFI)",
    },
    /* LP2 -- POWEROFF */
    [ZX_IDLE_CSTATE_LP2] =
    {
        .enter                = zx_enter_idle,
        .exit_latency        = LP2_DEFAULT_EXIT_LATENCY, 4500us
        .target_residency    = LP2_DEFAULT_EXIT_LATENCY+LP2_MIN_POWER_OFF_TIME, 5000us
        .flags                = CPUIDLE_FLAG_TIME_VALID,
        .name                = "LP2",
        .desc                = "POWEROFF",
    },
};

cpu_idle在start_kernel->rest_init->cpu_idle->while(1)中调用。cpu_idle调用cpuidle_idle_call：

cpu_idle->cpuidle_idle_call-|->trace_cpu_idle_rcuidle(next_state, dev->cpu);
|->trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, dev->cpu);

cpuidle_curr_governor->select(drv, dev) 根据当前的governor，选择合适的cpuidle状态

entered_state = cpuidle_enter_state(dev, drv, next_state);

cpuidle_curr_governor->reflect(dev, entered_state)

cpuidle_curr_governor在cpuidle_switch_governor中进行设置，一个是在cpuidle_register_governor注册时的时候，另一个是在store_current_governor通过sysfs节点设置cpuidle governor的时候。由于默认使用的是menu_governor，下面就来重点分析一下：

static struct cpuidle_governor menu_governor = {
.name = "menu",
.rating = 20,
.enable = menu_enable_device,
.select = menu_select,
.reflect = menu_reflect,
.owner = THIS_MODULE,
};

》》》》》》》》》》》》》》》》》》》》》》》》》》》》》》》》》》》》》》》》》》》》》》》》》

cpuidle_enter_state是执行根据governor确定的状态执行，然后返回进入的状态值。

cpuidle_enable_device设置cpuidle_enter_ops的值，cpuidle_enter_ops = drv->en_core_tk_irqen?cpuidle_enter_tk:cpuidle_enter;

cpuidle_enter调用target_state->enter(dev, drv, index);，指向zx_enter_idle。

cpuidle core

cpuidle governors

cpufreq

cpufreq driver

drivers/soc/zte/power/zx-cpufreq.c

drvers/soc/zte/power/zx297520v3-cpufreq.c

设置cpufreq的DVFS数据，在struct zx_dvfs_info中。

struct zx_dvfs_info {
    unsigned int    freq_cur_idx;
    unsigned int    pll_safe_idx;
    unsigned int    max_support_idx;
    unsigned int    min_support_idx;
    struct clk    *cpu_clk;
    unsigned int    *volt_table;
    struct cpufreq_frequency_table    *freq_table;
    int (*set_freq)(unsigned int, unsigned int);
};

cpufreq driver想初始化DVFS通过调用zx29xx_cpufreq_init。

static int zx297520v3_cpufreq_init(struct zx_dvfs_info *info)
{
if(cpufreq_driver_inited)
return 0;

    cpu_clk = clk_get(NULL, "cpu_clk");
    if (IS_ERR(cpu_clk))
    {
        pr_info("[CPUFREQ] get cpu_clk error \n");
        return PTR_ERR(cpu_clk);
    }

    info->freq_cur_idx         = L1;
    info->pll_safe_idx         = L1;
    info->max_support_idx     = max_support_idx;
    info->min_support_idx     = min_support_idx;
    info->cpu_clk             = cpu_clk;
    info->volt_table         = zx297520v3_volt_table;
    info->freq_table         = zx297520v3_freq_table;
    info->set_freq             = zx297520v3_set_frequency;

cpufreq_driver_inited = 1;

    INIT_DELAYED_WORK_DEFERRABLE(&pm_freq_work, pm_freq_func);
    schedule_delayed_work(&pm_freq_work, PM_FREQ_DELAY);
    pr_info("[CPUFREQ] zx297520v2_cpufreq_init ok \n");
    return 0;
}

static int __init zx297520v3_freq_register(void)
{
zx29xx_cpufreq_init = zx297520v3_cpufreq_init;

return 0;
}

cpu_clk如下：

static struct zx29_hwclk cpu_work = {
    /*             reg_addr                bit_offset      bit_size    */
    .clk_en_reg ={0,                        0,          0},
    .clk_sel_reg={ZX_MATRIX_CRM_BASE+0x40,     0,             2},
    .clk_div_reg={0,                        0,          0},
};
DEFINE_ZX29_CLK(cpu_work,cpu_clk_ops,ARRAY_SIZE(cpu_clk_parents),cpu_clk_parents);

CLK_ZX29_CONFIG(NULL, "cpu_clk", &cpu_work_clk),

这里通过zx297520v3_volt_table和zx297520v3_freq_table来达到OPP的概念，zx297520v3_set_frequency作为设置频率的底层函数。

static unsigned int zx297520v3_volt_table[CPUFREQ_LEVEL_END] = {
1250000, 1150000, 1050000, /*975000, 950000,*/
};

static struct cpufreq_frequency_table zx297520v3_freq_table[] = { 实际的频率只有两种，而且不可以调压
    {L0, 624*1000},
    {L1, 312*1000},
    //{L2, 156*1000},
    {0, CPUFREQ_TABLE_END},
};

cpufreq governors

cpufreq core

cpu hotplug

由于是单核CPU，所以不能使用hotplug功能。

wakelock

kernel/power/main.c

#ifdef CONFIG_PM_WAKELOCKS
static ssize_t wake_lock_show(struct kobject *kobj,
                  struct kobj_attribute *attr,
                  char *buf)
{
    return pm_show_wakelocks(buf, true);
}

static ssize_t wake_lock_store(struct kobject *kobj,
                   struct kobj_attribute *attr,
                   const char *buf, size_t n)
{
    int error = pm_wake_lock(buf);
    return error ? error : n;
}

power_attr(wake_lock);

static ssize_t wake_unlock_show(struct kobject *kobj,
                struct kobj_attribute *attr,
                char *buf)
{
    return pm_show_wakelocks(buf, false);
}

static ssize_t wake_unlock_store(struct kobject *kobj,
                 struct kobj_attribute *attr,
                 const char *buf, size_t n)
{
    int error = pm_wake_unlock(buf);
    return error ? error : n;
}

power_attr(wake_unlock);

#endif /* CONFIG_PM_WAKELOCKS */

static struct attribute * g[] = {
…
#ifdef CONFIG_PM_WAKELOCKS
    &wake_lock_attr.attr,
    &wake_unlock_attr.attr,
#endif
…
    NULL,
};

kernel/power/wakelock.c

增加wakelock tracepoint

修改config.linux：

CONFIG_PM_DEBUG=y
CONFIG_PM_SLEEP_DEBUG=y
CONFIG_FTRACE=y
CONFIG_FUNCTION_TRACER=y
CONFIG_FUNCTION_GRAPH_TRACER=y
CONFIG_KPROBES=y
CONFIG_KPROBES_ON_FTRACE=y

修改include/trace/events/power.h，增加wakelock相关trace包括pm_wake_lock和pm_wake_unlock。

修改kernel/power/wakelock.c，在pm_wake_lock和pm_wake_unlock中添加trace。

Index: wakelock.c
===================================================================
--- wakelock.c    (revision 1887)
+++ wakelock.c    (working copy)
@@ -16,7 +16,9 @@
#include <linux/list.h>
#include <linux/rbtree.h>
#include <linux/slab.h>
+#include <trace/events/power.h>

+
static DEFINE_MUTEX(wakelocks_lock);

struct wakelock {
@@ -217,7 +219,7 @@
     } else {
         __pm_stay_awake(&wl->ws);
     }
-
+    trace_pm_wake_lock(buf);
     wakelocks_lru_most_recent(wl);

out:
@@ -249,6 +251,7 @@
         goto out;
     }
     __pm_relax(&wl->ws);
+    trace_pm_wake_unlock(buf);

     wakelocks_lru_most_recent(wl);
     wakelocks_gc();

Runtime PM

Suspend and Resume

Clock、Regulator

一个Linux平台PM功能初探

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首页 > 代码库 > 一个Linux平台PM功能初探

一个Linux平台PM功能初探

WatchDog

用户空间节点

时钟资源

platform设备代码

platform驱动代码

cpuidle

cpuidle driver

cpuidle core

cpuidle governors

cpufreq

cpufreq driver

cpufreq governors

cpufreq core

cpu hotplug

wakelock

增加wakelock tracepoint

Runtime PM

Suspend and Resume

Clock、Regulator

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