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// HW PWM upport via Linux PWM sysfs interface
//
// Copyright (C) 2019 Janne Grunau <janne-3d@jannau.net>
//
// This file may be distributed under the terms of the GNU GPLv3 license.
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h> // errno, ENOENT
#include "gpio.h" // struct gpio_pwm
#include "internal.h" // NSECS_PER_TICK
#include "command.h" // shutdown
#include "sched.h" // sched_shutdown
#define MAX_PWM (1 << 15)
DECL_CONSTANT("PWM_MAX", MAX_PWM);
#define HARD_PWM_START (1<<16)
#define HARD_PWM(chip, pin) (((chip)<<4) + (pin) + HARD_PWM_START)
#define HARD_PWM_TO_CHIP(hard_pwm) (((hard_pwm) - HARD_PWM_START) >> 4)
#define HARD_PWM_TO_PIN(hard_pwm) (((hard_pwm) - HARD_PWM_START) & 0xf)
DECL_ENUMERATION_RANGE("pin", "pwmchip0/pwm0", HARD_PWM(0, 0), 16);
DECL_ENUMERATION_RANGE("pin", "pwmchip1/pwm0", HARD_PWM(1, 0), 16);
DECL_ENUMERATION_RANGE("pin", "pwmchip2/pwm0", HARD_PWM(2, 0), 16);
DECL_ENUMERATION_RANGE("pin", "pwmchip3/pwm0", HARD_PWM(3, 0), 16);
DECL_ENUMERATION_RANGE("pin", "pwmchip4/pwm0", HARD_PWM(4, 0), 16);
DECL_ENUMERATION_RANGE("pin", "pwmchip5/pwm0", HARD_PWM(5, 0), 16);
DECL_ENUMERATION_RANGE("pin", "pwmchip6/pwm0", HARD_PWM(6, 0), 16);
DECL_ENUMERATION_RANGE("pin", "pwmchip7/pwm0", HARD_PWM(7, 0), 16);
#define PWM_PATH "/sys/class/pwm/pwmchip%u/pwm%u/%s"
#define PWM_PATH_BB "/sys/class/pwm/pwm-%u:%u/%s"
struct gpio_pwm gpio_pwm_setup(uint8_t pin, uint32_t cycle_time, uint16_t val)
{
char filename[256];
char scratch[16];
uint8_t chip_id = HARD_PWM_TO_CHIP(pin);
uint8_t pwm_id = HARD_PWM_TO_PIN(pin);
const char * pwm_path = PWM_PATH;
struct gpio_pwm g = {};
g.period = cycle_time * NSECS_PER_TICK;
// configure period/cycle time. Always in nanoseconds
snprintf(filename, sizeof(filename), pwm_path, chip_id, pwm_id, "period");
int fd = open(filename, O_WRONLY|O_CLOEXEC);
if (fd == -1 && errno == ENOENT) {
// upstream pwm control file does not exists try BeagleBoard scheme
pwm_path = PWM_PATH_BB;
snprintf(filename, sizeof(filename), pwm_path, chip_id, pwm_id,
"period");
fd = open(filename, O_WRONLY|O_CLOEXEC);
if (fd == -1) {
report_errno("pwm " PWM_PATH_BB "period for pin", pin);
goto fail;
}
} else if (fd == -1) {
report_errno("pwm " PWM_PATH "period for pin", pin);
goto fail;
}
snprintf(scratch, sizeof(scratch), "%u", cycle_time * NSECS_PER_TICK);
write(fd, scratch, strlen(scratch));
close(fd);
// write duty cycle
snprintf(filename, sizeof(filename), pwm_path, chip_id, pwm_id,
"duty_cycle");
fd = open(filename, O_WRONLY|O_CLOEXEC);
if (fd == -1) {
report_errno("pwm duty_cycle", fd);
goto fail;
}
g.fd = fd;
gpio_pwm_write(g, val);
// enable PWM
snprintf(filename, sizeof(filename), pwm_path, chip_id, pwm_id, "enable");
fd = open(filename, O_WRONLY|O_CLOEXEC);
if (fd == -1) {
close(g.fd);
report_errno("pwm enable", fd);
goto fail;
}
write(fd, "1", 2);
close(fd);
return g;
fail:
if (fd >= 0)
close(fd);
shutdown("Unable to config pwm device");
}
void gpio_pwm_write(struct gpio_pwm g, uint16_t val)
{
char scratch[16];
uint32_t duty_cycle = g.period * (uint64_t)val / MAX_PWM;
snprintf(scratch, sizeof(scratch), "%u", duty_cycle);
if (g.fd != -1) {
write(g.fd, scratch, strlen(scratch));
} else {
report_errno("pwm set duty_cycle", g.fd);
}
}
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