ARM 无法进入WFI 模式

sz su

我们的是使用OMAP138， ARM使用linux系统, DSP 是BIOS系统

现在想要让ARM 的linux 系统进入WFI 模式（ ARM Wait-For-Interrupt Sleep Mode）

按照omap-138的datasheet 介绍

You can enable the WFI mode via the CP15 register #7 using the following instruction:
• MCR p15, #0, <Rd>, c7, c0, #4
Once the ARM module transitions into the WFI mode, it will remain in this state until an interrupt
(IRQ/FIQ) occurs.
The following sequence exemplifies how to enter the WFI mode:
• Enable any interrupt (for example, an external interrupt) that you plan to use as the wake-up
to exit from the WFI mode.
• Enable the WFI mode using the following CP15 instruction:
– MCR p15, #0, r3, c7, c0, #4
The following sequence describes the procedure to wake-up from the WFI mode:
• To wake-up from the WFI mode, trigger any enabled interrupt (for example, an external inter
• The ARM’s PC jumps to the IRQ/FIQ vector and you must handle the interrupt in an interrup
routine (ISR).

我在linux 内核态执行了语句

asm ( " MCR p15, #0, r3, c7, c0, #4\n\t" );

但是系统并没有发生什么变化，供电的电流也没什么变化，好像并没有进入WFI模式

请问如何让arm的linux 进入WFI模式？

8 年多前

0 Shine 8 年多前

TI__Guru**** 357097 points

请问是否在supervisor模式下执行WFI语句吗？

To enable the WFI mode, the ARM needs to be in supervisor mode.

0 sz su 8 年多前回复 Shine

Prodigy 180 points

请问linux 下如何进去 supervisor mode ？是在软中断中吗

0 Shine 8 年多前回复 sz su

TI__Guru**** 357097 points

是的。
To enter supervisor mode from user mode, generate a software interrupt (SWI).

0 sz su 8 年多前回复 Shine

Prodigy 180 points

你好，我在内核定时器中执行了asm ( "MCR p15, #0, r3, c7, c0, #4\n\t" );语句，但是系统也是没什么变化的，

理论上内核定时器的执行是在软中断的，那么这条语句应该是supervisor mode 模式下执行的

static void wfi_timer_func(unsigned long arg)
{
printk("wfi_timer_func\n");
printk("asm start 111 \n");

    asm ( "    teq    r3, #0\n\t");
  asm ( "MCR p15, #0, r3, c7, c0, #4\n\t" );
  printk("asm end111\n");

// asm ( "mcr p15, #0, r1, c7, c0, #4\n\t" );
// printk("asm end222\n");

return 0;
}

struct timer_list wfitimer;

static int funcIn(void)
{
printk("funcIn\n");
// struct timer_list wfitimer;
  init_timer(&wfitimer);
  wfitimer.data = 0x1234;
  wfitimer.function = wfi_timer_func;
  wfitimer.expires = jiffies + msecs_to_jiffies(1000);
  add_timer(&wfitimer);

    return 0;
}

static void funcOut(void)
{
printk("funcIn\n");
return;
}

理论上内核定时器的执行是在软中断的，那么这条语句应该是supervisor mode 模式下执行的

但是系统依旧没什么变化，我的执行过程是否有什么问题

在TI 的官网上，找到进入WFI 的示例代码，如下

int main(void)
{

printf("OMAPL138 is in WFI mode. Insert/Remove the SD card to generate interrupt for wakeup.\n");

    /* The Local PSC number for GPIO is 3. GPIO belongs to PSC1 module.*/
    PSCModuleControl(SOC_PSC_1_REGS, HW_PSC_GPIO, PSC_POWERDOMAIN_ALWAYS_ON,
             PSC_MDCTL_NEXT_ENABLE);

/* Pin Multiplexing of pins GP6[12], GP6[13], GP2[12], GP0[9], for LEDs in OMAPL138 LCDK board */
PinMuxSetup_leds();

/* LEDs SETUP */

/* Sets the pin 109 (GP6[12]) as output.*/
GPIODirModeSet(SOC_GPIO_0_REGS, 109, GPIO_DIR_OUTPUT);

/* Sets the pin 110 (GP6[13]) as output.*/
GPIODirModeSet(SOC_GPIO_0_REGS, 110, GPIO_DIR_OUTPUT);

/* Sets the pin 45 (GP2[12]) as output.*/
GPIODirModeSet(SOC_GPIO_0_REGS, 45, GPIO_DIR_OUTPUT);

/* Sets the pin 10 (GP0[9]) as output.*/
GPIODirModeSet(SOC_GPIO_0_REGS, 10, GPIO_DIR_OUTPUT);

/* Initializes the UART instance.*/
UARTStdioInit();

/* Pin Multiplexing of pin 0 of GPIO Bank 4.*/
GPIOBank4Pin0PinMuxSetup();

/* Sets the pin 65(GP4[0]) as input.*/
GPIODirModeSet(SOC_GPIO_0_REGS, 65, GPIO_DIR_INPUT);

    /*
    ** Configure rising edge and falling edge triggers on pin 65 to generate
    ** an interrupt
    */
    GPIOIntTypeSet(SOC_GPIO_0_REGS, 65, GPIO_INT_TYPE_BOTHEDGE);

/* Enable interrupts for Bank 4.*/
GPIOBankIntEnable(SOC_GPIO_0_REGS, 4);

/* Configuring the AINTC to handle interrupts.*/
SetupInt();

/* Configure GPIO interrupts */
ConfigureIntGPIO();

//UARTPuts("StarterWare GPIO Demo Application.\r\n", -2);
//UARTPuts("Insert an MMC/SD card.\r\n", -2);

printf("StarterWare GPIO Demo Application\n");
printf("Insert an MMC/SD card.\n");

//Titus : ARM WFI code
SysCfgRegistersUnlock();

asm ( " teq r1, #0\n\t");

asm ( " mcr p15, #0, r1, c7, c0, #4\n\t" );

//Here, code get stuck due to WFI and it resume when SD card interrupt raised.

SysCfgRegistersLock();

//LED D5 would glow when ARM comes out of WFI mode (i.e, when interrupt generated).
GPIOPinWrite(SOC_GPIO_0_REGS, 109, GPIO_PIN_HIGH);

printf("Comes out of WFI mode; Resume to normal operation.\n");

    while(1)
    {
        if(flag == 1)
        {
            CheckCardStatus();
        }
    }

}

这边是否有完整的代码？

以及SysCfgRegistersUnlock();和 SysCfgRegistersLock();

这些函数具体都完成了什么功能呢

请帮忙看看，谢谢啦

0 Shine 8 年多前回复 sz su

TI__Guru**** 357097 points

置顶贴里有基于starterware的示例。
http://www.deyisupport.com/question_answer/dsp_arm/omap_l1x/f/54/t/103692.aspx

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ARM 无法进入WFI 模式