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前言:
最近在使用Widora mt7688开发板的时候,发现OpenWRT默认的GPIＯ驱动非常恼人，只提供了sysfs默认的调用接口。编程时需要和一堆文件打交道，用来做做简单的gpio开发是够了，但是要实现复杂点的逻辑这套就显得力不从心和不优雅了。
所以就萌生了在用户态实现gpio驱动的想法，其实思路非常简单，无非就是先mmap mt7628/mt7688的寄存器，这样就可以直接在用户态实现对gpio的访问和控制。使用mmap的好处其实挺多的：第一通用可以在OpenWRT和SDK上运行，不需要考虑系统的差异性。第二性能相比sysfs的模式，可以得到明显的提升。使用示波器测试gpio产生方波可以到7.4M。下面是截图
代码部分:
我实现了几个基本的操作，一个是gpio_set_pin_direction 用来设置gpio的输入和输出模式，一个是gpio_get_pin用来获取gpio的输入状态，另一个是gpio_set_pin_value用来设置gpio的输出值。代码部分参考了sdk里驱动的实现，和内核态的驱动几乎一致。
/* forgotfun.org 佐须之男 */
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#define MMAP_PATH "/dev/mem"
#define RALINK_GPIO_DIR_IN 0
#define RALINK_GPIO_DIR_OUT 1
#define RALINK_REG_PIOINT 0x690
#define RALINK_REG_PIOEDGE 0x6A0
#define RALINK_REG_PIORENA 0x650
#define RALINK_REG_PIOFENA 0x660
#define RALINK_REG_PIODATA 0x620
#define RALINK_REG_PIODIR 0x600
#define RALINK_REG_PIOSET 0x630
#define RALINK_REG_PIORESET 0x640
#define RALINK_REG_PIO6332INT 0x694
#define RALINK_REG_PIO6332EDGE 0x6A4
#define RALINK_REG_PIO6332RENA 0x654
#define RALINK_REG_PIO6332FENA 0x664
#define RALINK_REG_PIO6332DATA 0x624
#define RALINK_REG_PIO6332DIR 0x604
#define RALINK_REG_PIO6332SET 0x634
#define RALINK_REG_PIO6332RESET 0x644
#define RALINK_REG_PIO9564INT 0x698
#define RALINK_REG_PIO9564EDGE 0x6A8
#define RALINK_REG_PIO9564RENA 0x658
#define RALINK_REG_PIO9564FENA 0x668
#define RALINK_REG_PIO9564DATA 0x628
#define RALINK_REG_PIO9564DIR 0x608
#define RALINK_REG_PIO9564SET 0x638
#define RALINK_REG_PIO9564RESET 0x648
static uint8_t* gpio_mmap_reg = NULL;
static int gpio_mmap_fd = 0;
static int gpio_mmap(void)
{
if ((gpio_mmap_fd = open(MMAP_PATH, O_RDWR)) < 0) {
fprintf(stderr, "unable to open mmap file");
return -1;
}
gpio_mmap_reg = (uint8_t*) mmap(NULL, 1024, PROT_READ | PROT_WRITE,
MAP_FILE | MAP_SHARED, gpio_mmap_fd, 0x10000000);
if (gpio_mmap_reg == MAP_FAILED) {
perror("foo");
fprintf(stderr, "failed to mmap");
gpio_mmap_reg = NULL;
close(gpio_mmap_fd);
return -1;
}
return 0;
}
int mt76x8_gpio_get_pin(int pin)
{
uint32_t tmp = 0;
/* MT7621, MT7628 */
if (pin <= 31) {
tmp = *(volatile uint32_t *)(gpio_mmap_reg + RALINK_REG_PIODATA);
tmp = (tmp >> pin) & 1u;
} else if (pin <= 63) {
tmp = *(volatile uint32_t *)(gpio_mmap_reg + RALINK_REG_PIO6332DATA);
tmp = (tmp >> (pin-32)) & 1u;
} else if (pin <= 95) {
tmp = *(volatile uint32_t *)(gpio_mmap_reg + RALINK_REG_PIO9564DATA);
tmp = (tmp >> (pin-64)) & 1u;
tmp = (tmp >> (pin-24)) & 1u;
}
return tmp;
}
void mt76x8_gpio_set_pin_direction(int pin, int is_output)
{
uint32_t tmp;
/* MT7621, MT7628 */
if (pin <= 31) {
tmp = *(volatile uint32_t *)(gpio_mmap_reg + RALINK_REG_PIODIR);
if (is_output)
tmp |= (1u << pin);
else
tmp &= ~(1u << pin);
*(volatile uint32_t *)(gpio_mmap_reg + RALINK_REG_PIODIR) = tmp;
} else if (pin <= 63) {
tmp = *(volatile uint32_t *)(gpio_mmap_reg + RALINK_REG_PIO6332DIR);
if (is_output)
tmp |= (1u << (pin-32));
else
tmp &= ~(1u << (pin-32));
*(volatile uint32_t *)(gpio_mmap_reg + RALINK_REG_PIO6332DIR) = tmp;
} else if (pin <= 95) {
tmp = *(volatile uint32_t *)(gpio_mmap_reg + RALINK_REG_PIO9564DIR);
if (is_output)
tmp |= (1u << (pin-64));
else
tmp &= ~(1u << (pin-64));
*(volatile uint32_t *)(gpio_mmap_reg + RALINK_REG_PIO9564DIR) = tmp;
}
}
void mt76x8_gpio_set_pin_value(int pin, int value)
{
uint32_t tmp;
/* MT7621, MT7628 */
if (pin <= 31) {
tmp = (1u << pin);
if (value)
*(volatile uint32_t *)(gpio_mmap_reg + RALINK_REG_PIOSET) = tmp;
else
*(volatile uint32_t *)(gpio_mmap_reg + RALINK_REG_PIORESET) = tmp;
} else if (pin <= 63) {
tmp = (1u << (pin-32));
if (value)
*(volatile uint32_t *)(gpio_mmap_reg + RALINK_REG_PIO6332SET) = tmp;
else
*(volatile uint32_t *)(gpio_mmap_reg + RALINK_REG_PIO6332RESET) = tmp;
} else if (pin <= 95) {
tmp = (1u << (pin-64));
if (value)
*(volatile uint32_t *)(gpio_mmap_reg + RALINK_REG_PIO9564SET) = tmp;
else
*(volatile uint32_t *)(gpio_mmap_reg + RALINK_REG_PIO9564RESET) = tmp;
}
}
int main(int argc, char **argv)
{
int ret = -1;
if (gpio_mmap())
return -1;
printf("get pin 39 input %d\n", mt76x8_gpio_get_pin(39));
printf("get pin 40 input %d\n", mt76x8_gpio_get_pin(40));
printf("get pin 41 input %d\n", mt76x8_gpio_get_pin(41));
printf("get pin 42 input %d\n", mt76x8_gpio_get_pin(42));
printf("set pin 39 output 1\n");
mt76x8_gpio_set_pin_direction(39, 1);
mt76x8_gpio_set_pin_value(39, 1);
printf("set pin 40 output 0\n");
mt76x8_gpio_set_pin_direction(40, 1);
mt76x8_gpio_set_pin_value(40, 0);
printf("set pin 41 output 1\n");
mt76x8_gpio_set_pin_direction(41, 1);
mt76x8_gpio_set_pin_value(41, 1);
printf("set pin 42 output 0\n");
mt76x8_gpio_set_pin_direction(42, 1);
mt76x8_gpio_set_pin_value(42, 0);
while (1)
{
mt76x8_gpio_set_pin_value(42, 0);
mt76x8_gpio_set_pin_value(42, 1);
}
close(gpio_mmap_fd);
return ret;
}更多代码可以到 https://github.com/ForgotFun/mt76x8 下载，如有疑问可邮件联系。