Analysis of LED Driver of Marvell (Marvell PXA310 LED驱动代码分析)

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1. Abstract

抱歉这篇报告是我当初用英文写的，有兴趣的朋友可以参考。

2. Introduction

3. Driver Codes

Codes exist indrivers/misc/misc_control.c.

3.1 Data Structure

The devicestructure in

3.2 InitializeCodes

3.2.1 Probe Function

Codes exist in drivers/misc/misc_control.c.

static int mctl_probe(struct platform_device *pdev)

{

struct resource *res;

int ret;

mctl_hardware_init();

res = platform_get_resource(pdev,IORESOURCE_MEM, 0); //This line is no sense since wehave not registered any IO resources.

ret = misc_register(&misc_control_dev);

……

return 0;

}

static int mctl_hardware_init(void)

{

pxa3xx_mfp_set_configs(misc_ctl_pins, ARRAY_SIZE(misc_ctl_pins));//Please refer to section 3.4.1 and 3.4.2

pxa3xx_gpio_set_direction(WIFI_LED_GPIO,GPIO_DIR_OUT);

pxa3xx_gpio_set_level(WIFI_LED_GPIO,0);

pxa3xx_gpio_set_direction(BT_LED_GPIO,GPIO_DIR_OUT);

pxa3xx_gpio_set_level(BT_LED_GPIO,0);

pxa3xx_gpio_set_direction(POWER_RED_LED_GPIO,GPIO_DIR_OUT);

pxa3xx_gpio_set_level(POWER_RED_LED_GPIO,0);

pxa3xx_gpio_set_direction(POWER_GREEN_LED_GPIO,GPIO_DIR_OUT);

pxa3xx_gpio_set_level(POWER_GREEN_LED_GPIO,0);

pxa3xx_gpio_set_direction(POWER_BLUE_LED_GPIO,GPIO_DIR_OUT);

pxa3xx_gpio_set_level(POWER_BLUE_LED_GPIO,0);

// Do reset for bluetoothchip

mctl_bt_do_reset(); //It seemed that GPIO BT_RESET_GPIO is used to reset BTmodule

return 0;

}

3.3 DriverOperation Codes

The following data structure is initialized in misc_register.

static const struct file_operations mctl_fops = {

owner:THIS_MODULE,

open:mctl_open,

release:mctl_release,

read:mctl_read,

write:mctl_write,

fasync:NULL,

poll:NULL,

ioctl:mctl_ioctl,

llseek:no_llseek,

};

All functions except mctl_ioctl are empty.

static int mctl_ioctl(struct inode *inode, struct file *file, unsignedint cmd,

unsigned long arg)

{

int ret;

void __user *argp = (void__user *)arg;

struct misc_ctl_structm_ctl;

switch (cmd) {

case MCTL_GET_CTL:

if(copy_from_user(&m_ctl, argp, sizeof(m_ctl)))

return-EFAULT;

ret = do_mctl_get(&m_ctl); //Fetch the currentvalue, all of them are the current settings of GPIO

if (ret)

return ret;

returncopy_to_user(argp, &m_ctl, sizeof(m_ctl));

break;

case MCTL_SET_CTL:

if(copy_from_user(&m_ctl, argp, sizeof(m_ctl)))

return-EFAULT;

ret = do_mctl_set(&m_ctl); //Set the value of theLED, which will be explained later.

if (ret)

return ret;

return 0;

break;

default:

return -EINVAL;

}

return 0;

}

static int do_mctl_set(struct misc_ctl_struct *m_ctl)

{

switch(m_ctl->ctrl){

caseCTRL_POWER_RED_LED:

pxa3xx_gpio_set_level(POWER_RED_LED_GPIO,!!m_ctl->val);

break;

caseCTRL_POWER_GREEN_LED:

mctl_set_power_led_mode(m_ctl->val); //We will explain it later.

break;

caseCTRL_POWER_BLUE_LED:

pxa3xx_gpio_set_level(POWER_BLUE_LED_GPIO,!!m_ctl->val);

break;

case CTRL_WIFI_LED:

pxa3xx_gpio_set_level(WIFI_LED_GPIO,!!m_ctl->val);

break;

case CTRL_BT_LED:

pxa3xx_gpio_set_level(BT_LED_GPIO,!!m_ctl->val);

break;

case CTRL_BT_RESET:

if (m_ctl->val != 0)

mctl_bt_do_reset();

break;

……

}

return 0;

}

int mctl_set_power_led_mode(int setting)

{

power_led_flip_mode = (setting & POWER_LED_MODE_MASK); //Get the flip mode

//From now we compute the flip interval,or set it to 0 if no flip need.

if (power_led_flip_mode & (POWER_LED_MODE_NORMAL | POWER_LED_MODE_SLEEP ) ) {

power_led_flip_interval= ( setting & POWER_LED_VALUE_MASK );

if(!power_led_flip_interval)

power_led_flip_interval= 2; // set default filping interval to2 seconds.

}else{

power_led_flip_interval= 0;

}

if (power_led_flip_mode& POWER_LED_MODE_NORMAL) { //This is very strange,since we should also enable flip mode in POWER_LED_MODE_SLEEP

mctl_enable_power_led_flip_hardware(); //Please refer to section 3.5

return 0;

}

mctl_disable_power_led_flip_hardware(); //Disable flip now.

// as long as GPIO mode isset and normal mode is not set. we control led with 0/1 through GPIO in fullpower state

if (power_led_flip_mode &POWER_LED_MODE_GPIO ) {

pxa3xx_gpio_set_level(POWER_GREEN_LED_GPIO,!!( setting & POWER_LED_VALUE_MASK ));

return 0;

}

// if only flip during sleepmode is set, we disable led in full power state.

if (power_led_flip_mode &POWER_LED_MODE_SLEEP) { //Close the LED during Sleepmode.

pxa3xx_gpio_set_level(POWER_GREEN_LED_GPIO,0);

return 0;

}

return -EINVAL;

}

3.4 The PinDescriptions

3.4.1 Function pxa3xx_mfp_set_config

First of all, let us see the data structure of pxa3xx_pin_config:

struct pxa3xx_pin_config {

unsigned int mfp_pin; //The Pin register

unsignedint reserved:16;

unsigned int af_sel:3; //select the function of this pin

unsigned int edge_rise_en:1; //enable rise edge detection.

unsigned int edge_fall_en:1; //enable fall edge detection.

unsigned int edge_clear:1; //enable edge detection.

unsigned int sleep_oe_n:1; //determine the direction of this pin in low power mode.

unsigned int sleep_data:1; //the output data in low power mode.

unsigned int sleep_sel:1; //enable low power mode output.

unsigned int drive:3; //Drive strength and slew rate

unsigned int pulldown_en:1; //enable pull down function

unsigned int pullup_en:1; //enable pull up function

unsigned int pull_sel:1; //enable pull function

};

Please refer to document [1] P129 Section 4.11 forconcrete meaning of these fields.

#define PIN2REG(pin_config) /

(pin_config->af_sel<< MFPR_ALT_OFFSET) | /

(pin_config->edge_rise_en << MFPR_ERE_OFFSET ) |/

(pin_config->edge_fall_en << MFPR_EFE_OFFSET ) |/

(pin_config->edge_clear << MFPR_EC_OFFSET ) | /

(pin_config->sleep_oe_n << MFPR_SON_OFFSET ) | /

(pin_config->sleep_data << MFPR_SD_OFFSET ) | /

(pin_config->sleep_sel << MFPR_SS_OFFSET ) | /

(pin_config->drive << MFPR_DRV_OFFSET ) | /

(pin_config->pulldown_en << MFPR_PD_OFFSET ) | /

(pin_config->pullup_en << MFPR_PU_OFFSET ) | /

(pin_config->pull_sel << MFPR_PS_OFFSET );

And now you should understand the meaning of functionpxa3xx_mfp_set_config.

3.4.2 Data Structure misc_ctl_pins

struct pxa3xx_pin_config misc_ctl_pins[] = {

PXA3xx_MFP_CFG("Wifi_LED", WIFI_LED_GPIO, MFP_AF0, MFP_DS01X, 0, MFP_LPM_PULL_LOW, MFP_EDGE_NONE),

PXA3xx_MFP_CFG("Bluetooth _LED", BT_LED_GPIO, MFP_AF0,MFP_DS01X, 0, MFP_LPM_PULL_LOW, MFP_EDGE_NONE),

PXA3xx_MFP_CFG("POWER_RED_LED", POWER_RED_LED_GPIO, MFP_AF0,MFP_DS01X, 0, MFP_LPM_PULL_LOW, MFP_EDGE_NONE),

PXA3xx_MFP_CFG("POWER_GREEN_LED", POWER_GREEN_LED_GPIO, MFP_AF0,MFP_DS01X, 0, MFP_LPM_PULL_LOW, MFP_EDGE_NONE),

PXA3xx_MFP_CFG("POWER_BLUE_LED", POWER_BLUE_LED_GPIO, MFP_AF0,MFP_DS01X, 0, MFP_LPM_PULL_LOW, MFP_EDGE_NONE),

PXA3xx_MFP_CFG("BT_RESET", BT_RESET_GPIO, MFP_AF0, MFP_DS01X, 0, MFP_LPM_PULL_HIGH,MFP_EDGE_NONE),

};

#define PXA3xx_MFP_CFG(desc, pin, af, drv, rdh, lpm, edge) /

{ /

.mfp_pin = pin, /

.af_sel = af, /

.reserved = 0, /

.drive = drv, /

.sleep_sel = rdh, /

.sleep_oe_n = ((lpm) & 0x1), /

.sleep_data = (((lpm) & 0x2) >>1), /

.pullup_en = (((lpm) & 0x4) >>2), /

.pulldown_en = (((lpm) & 0x8) >>3), /

.pull_sel = (((lpm) & 0x10) >>4), /

.edge_clear = (!(edge)), /

.edge_fall_en = ((edge) & 0x1), /

.edge_rise_en = (((edge) & 0x2) >>1), /

}

3.4.3 Function pxa3xx_mfp_set_afds

static voidmctl_disable_power_led_flip_hardware(void)

{

OMCR10 = 0;

// set pin back to GPIO

pxa3xx_mfp_set_afds(POWER_GREEN_LED_GPIO, MFP_AF0, MFP_DS01X);//Please refer to following, When it is not used,reset the multi-function PIN of GPIO19 to 0, which is the primary function ofit: GPIO_19. See the explanation in Section 3.5

}

intpxa3xx_mfp_set_afds(unsigned int pin, int af, int ds)

{

//dsis driver strength, in our case it is always 0. Please refer to document [1]P130 for details.

uint32_t mfp_reg;

unsigned long flags;

#if defined(CONFIG_PXA3xx_GPIOEX)

if (IS_GPIO_EXP_PIN(pin))

return 0;

#endif

spin_lock_irqsave(&mfp_spin_lock,flags);

mfp_reg = MFP_REG(pin); //Get the PIN Address, which isstarted from 0x40E1_0000

mfp_reg &= ~(MFP_AF_MASK | MFP_DRV_MASK); //Clear AF and DRV fields

mfp_reg |= (((af & 0x7) << MFPR_ALT_OFFSET) |

((ds &0x7) << MFPR_DRV_OFFSET)); //Then set AF and DRVfields, AF is the function fields, and DRV is the driver strength fields

MFP_REG(pin) = mfp_reg;

mfp_reg = MFP_REG(pin);

spin_unlock_irqrestore(&mfp_spin_lock,flags);

return 0;

}

3.5 The OperatingSystem Timers

3.5.1 Function mctl_enable_power_led_flip_hardware

Please refer to document [1] P418 Section 11.4 fordetails.

static void mctl_enable_power_led_flip_hardware(void)

{

if ( power_led_flip_interval== 0 )

return;

// set pin to ostimer 10chout 0

pxa3xx_mfp_set_afds(POWER_GREEN_LED_GPIO, MFP_AF6, MFP_DS01X);//Please refer to section 3.4.3

//#definePOWER_GREEN_LED_GPIO (MFP_PIN_GPIO19)

//#define MFP_PIN_GPIO19 ((0x02BC << 16) | (19))

//From document [1]Section 4.7.3, you may found that the PIN is GPIO19;and then in document [1] Section 4.4 (P76) you may found the function multiplexer of this PIN, in our case itshould be CHOUT0, which is 6.

OMCR10 = 0; //Reset channel 10

OSMR10 = power_led_flip_interval; //Setthe time match register of channel 10.

OSCR10 = 0; //reset counter value;

OMCR10 = ( OMCR_R | OMCR_P | OMCR_C | OMCR_CRES_SEC ); // OMCR_R means reset the timer on match, OMCR_P means it isa periodic timer, OMCR_C means channel to match against is OSCRx, OMCR_CRES_SECis 3 (0X11), and therefore means the counter resolution is 1 second.

OSCR10 = 0; //set again to trigger the counting.

}

3.5.2 How to Find the Meaning of Multi-Function Pin

From the above section, we can understand how tofind the meaning of MFP.

First, from the codes, you can get the address ofthis PIN;

Then go into document [1] Section 4.7.3,find the name of this PIN;

Then go into document [1] Section 4.4, find themultiplexed function of this named PIN;

Then go into document [1] Section 4.11, to checkout how to set the register.

4. Future Works

I do not know if following works are necessary:

5. Questions

6. References

[1]. PXA3xx_Processor_Family_Developer_Manual_Vol._I_Version_1.0_Rev._C.pdf