UM0851 datasheet(211/245 Pages) STMICROELECTRONICS

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UM0851

Miscellaneous device drivers

Doc ID 16604 Rev 2

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You can get an interrupt line number for the GPIO pin to be used in interrupt mode. You can

also get the GPIO pin number from the interrupt line number (for GPIOs used in interrupt

mode). This can be done using following function:

/* This function returns irq no. for gpio pin */

int gpio_to_irq(unsigned gpio);

/* This function returns gpio pin for irq no. */

int irq_to_gpio(unsigned irq);

To request a GPIO in interrupt mode you should use the standard linux request_irq()

function.

/* Here,

irq: is irq no. value returned from gpio_to_irq().

handler: irq handler with standard prototype.

Irqflags: flags passed for configuring type of interrupt, it can be one

of following:

IRQ_TYPE_EDGE_RISING, IRQ_TYPE_EDGE_FALLING, IRQ_TYPE_EDGE_BOTH,

IRQ_TYPE_LEVEL_HIGH, IRQ_TYPE_LEVEL_LOW

Devname: name of device requesting interrupt

Dev_id: pointer passed to interrupt handler upon interrupt.

int request_irq(unsigned int irq, irq_handler_t handler, unsigned long

irqflags, const char *devname, void *dev_id);

After use, the GPIO interrupt can be freed using the following function call:

/* irq: is irq no. value returned from gpio_to_irq().

Dev_id: pointer passed to interrupt handler upon interrupt. */

void free_irq(unsigned int irq, void *dev_id);

9.1.6

Configuration options

9.2

Watchdog (WDT) driver

A Watchdog timer is a hardware device that triggers a system reset if its regularly generated

interrupts are not acknowledged. The idea behind it is to have an reliable way to bring the

system back from the hung state into normal operation.

9.2.1

Hardware overview

SPEAr platform provides a watchdog timer which has a 32- bit down counter with a

programmable timeout value. On timeout it generates an interrupt and reset signal. The

Table 55.

GPIO kernel configuration options

Configuration option

Comment

ARCH_REQUIRE_GPIOLIB

Selecting this from the architecture code will cause the gpiolib code to

always get built in.

GPIOLIB

This enables GPIO support through the generic GPIO library.

GPIO_SYSFS

This enables the sysfs interface for GPIOs

CONFIG_SPEAR_GPIO

This enables the SPEAr GPIO

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