ws2812_gpio.c

/*
 * Copyright (c) 2018 Intel Corporation
 * Copyright (c) 2019 Nordic Semiconductor ASA
 * Copyright (c) 2021 Seagate Technology LLC
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#define DT_DRV_COMPAT worldsemi_ws2812_gpio

#include <zephyr/drivers/led_strip.h>

#include <string.h>

#define LOG_LEVEL CONFIG_LED_STRIP_LOG_LEVEL
#include <zephyr/logging/log.h>
LOG_MODULE_REGISTER(ws2812_gpio);

#include <zephyr/kernel.h>
#include <soc.h>
#include <zephyr/drivers/gpio.h>
#include <zephyr/device.h>
#include <zephyr/drivers/clock_control.h>
#include <zephyr/drivers/clock_control/nrf_clock_control.h>
#include <zephyr/dt-bindings/led/led.h>

struct ws2812_gpio_cfg {
	struct gpio_dt_spec in_gpio;
	uint8_t num_colors;
	const uint8_t *color_mapping;
};

/*
 * This is hard-coded to nRF51 in two ways:
 *
 * 1. The assembly delays T1H, T0H, TxL
 * 2. GPIO set/clear
 */

/*
 * T1H: 1 bit high pulse delay: 12 cycles == .75 usec
 * T0H: 0 bit high pulse delay: 4 cycles == .25 usec
 * TxL: inter-bit low pulse delay: 8 cycles == .5 usec
 *
 * We can't use k_busy_wait() here: its argument is in microseconds,
 * and we need roughly .05 microsecond resolution.
 */
#define DELAY_T1H "nop\nnop\nnop\nnop\nnop\nnop\nnop\nnop\nnop\nnop\nnop\nnop\n"
#define DELAY_T0H "nop\nnop\nnop\nnop\n"
#define DELAY_TxL "nop\nnop\nnop\nnop\nnop\nnop\nnop\nnop\n"

/*
 * GPIO set/clear (these make assumptions about assembly details
 * below).
 *
 * This uses OUTCLR == OUTSET+4.
 *
 * We should be able to make this portable using the results of
 * https://github.com/zephyrproject-rtos/zephyr/issues/11917.
 *
 * We already have the GPIO device stashed in ws2812_gpio_config, so
 * this driver can be used as a test case for the optimized API.
 *
 * Per Arm docs, both Rd and Rn must be r0-r7, so we use the "l"
 * constraint in the below assembly.
 */
#define SET_HIGH "str %[p], [%[r], #0]\n" /* OUTSET = BIT(LED_PIN) */
#define SET_LOW "str %[p], [%[r], #4]\n"  /* OUTCLR = BIT(LED_PIN) */

/* Send out a 1 bit's pulse */
#define ONE_BIT(base, pin) do {			\
	__asm volatile (SET_HIGH			\
			DELAY_T1H			\
			SET_LOW			\
			DELAY_TxL			\
			::				\
			[r] "l" (base),		\
			[p] "l" (pin)); } while (false)

/* Send out a 0 bit's pulse */
#define ZERO_BIT(base, pin) do {			\
	__asm volatile (SET_HIGH			\
			DELAY_T0H			\
			SET_LOW			\
			DELAY_TxL			\
			::				\
			[r] "l" (base),		\
			[p] "l" (pin)); } while (false)

static int send_buf(const struct device *dev, uint8_t *buf, size_t len)
{
	const struct ws2812_gpio_cfg *config = dev->config;
	volatile uint32_t *base = (uint32_t *)&NRF_GPIO->OUTSET;
	const uint32_t val = BIT(config->in_gpio.pin);
	struct onoff_manager *mgr =
		z_nrf_clock_control_get_onoff(CLOCK_CONTROL_NRF_SUBSYS_HF);
	struct onoff_client cli;
	unsigned int key;
	int rc;

	sys_notify_init_spinwait(&cli.notify);
	rc = onoff_request(mgr, &cli);
	if (rc < 0) {
		return rc;
	}

	while (sys_notify_fetch_result(&cli.notify, &rc)) {
		/* pend until clock is up and running */
	}

	key = irq_lock();

	while (len--) {
		uint32_t b = *buf++;
		int32_t i;

		/*
		 * Generate signal out of the bits, MSbit first.
		 *
		 * Accumulator maintenance and branching mean the
		 * inter-bit time will be longer than TxL, but the
		 * wp.josh.com blog post says we have at least 5 usec
		 * of slack time between bits before we risk the
		 * signal getting latched, so this will be fine as
		 * long as the compiler does something minimally
		 * reasonable.
		 */
		for (i = 7; i >= 0; i--) {
			if (b & BIT(i)) {
				ONE_BIT(base, val);
			} else {
				ZERO_BIT(base, val);
			}
		}
	}

	irq_unlock(key);

	rc = onoff_release(mgr);
	/* Returns non-negative value on success. Cap to 0 as API states. */
	rc = MIN(rc, 0);

	return rc;
}

static int ws2812_gpio_update_rgb(const struct device *dev,
				  struct led_rgb *pixels,
				  size_t num_pixels)
{
	const struct ws2812_gpio_cfg *config = dev->config;
	uint8_t *ptr = (uint8_t *)pixels;
	size_t i;

	/* Convert from RGB to on-wire format (e.g. GRB, GRBW, RGB, etc) */
	for (i = 0; i < num_pixels; i++) {
		uint8_t j;

		for (j = 0; j < config->num_colors; j++) {
			switch (config->color_mapping[j]) {
			/* White channel is not supported by LED strip API. */
			case LED_COLOR_ID_WHITE:
				*ptr++ = 0;
				break;
			case LED_COLOR_ID_RED:
				*ptr++ = pixels[i].r;
				break;
			case LED_COLOR_ID_GREEN:
				*ptr++ = pixels[i].g;
				break;
			case LED_COLOR_ID_BLUE:
				*ptr++ = pixels[i].b;
				break;
			default:
				return -EINVAL;
			}
		}
	}

	return send_buf(dev, (uint8_t *)pixels, num_pixels * config->num_colors);
}

static int ws2812_gpio_update_channels(const struct device *dev,
				       uint8_t *channels,
				       size_t num_channels)
{
	LOG_ERR("update_channels not implemented");
	return -ENOTSUP;
}

static const struct led_strip_driver_api ws2812_gpio_api = {
	.update_rgb = ws2812_gpio_update_rgb,
	.update_channels = ws2812_gpio_update_channels,
};

/*
 * Retrieve the channel to color mapping (e.g. RGB, BGR, GRB, ...) from the
 * "color-mapping" DT property.
 */
#define WS2812_COLOR_MAPPING(idx)					\
static const uint8_t ws2812_gpio_##idx##_color_mapping[] =		\
	DT_INST_PROP(idx, color_mapping)

#define WS2812_NUM_COLORS(idx) (DT_INST_PROP_LEN(idx, color_mapping))

/*
 * The inline assembly above is designed to work on nRF51 devices with
 * the 16 MHz clock enabled.
 *
 * TODO: try to make this portable, or at least port to more devices.
 */

#define WS2812_GPIO_DEVICE(idx)					\
									\
	static int ws2812_gpio_##idx##_init(const struct device *dev)	\
	{								\
		const struct ws2812_gpio_cfg *cfg = dev->config;	\
		uint8_t i;						\
									\
		if (!gpio_is_ready_dt(&cfg->in_gpio)) {		\
			LOG_ERR("GPIO device not ready");		\
			return -ENODEV;					\
		}							\
									\
		for (i = 0; i < cfg->num_colors; i++) {			\
			switch (cfg->color_mapping[i]) {		\
			case LED_COLOR_ID_WHITE:			\
			case LED_COLOR_ID_RED:				\
			case LED_COLOR_ID_GREEN:			\
			case LED_COLOR_ID_BLUE:				\
				break;					\
			default:					\
				LOG_ERR("%s: invalid channel to color mapping." \
					" Check the color-mapping DT property",	\
					dev->name);			\
				return -EINVAL;				\
			}						\
		}							\
									\
		return gpio_pin_configure_dt(&cfg->in_gpio, GPIO_OUTPUT); \
	}								\
									\
	WS2812_COLOR_MAPPING(idx);					\
									\
	static const struct ws2812_gpio_cfg ws2812_gpio_##idx##_cfg = { \
		.in_gpio = GPIO_DT_SPEC_INST_GET(idx, in_gpios),	\
		.num_colors = WS2812_NUM_COLORS(idx),			\
		.color_mapping = ws2812_gpio_##idx##_color_mapping,	\
	};								\
									\
	DEVICE_DT_INST_DEFINE(idx,					\
			    ws2812_gpio_##idx##_init,			\
			    NULL,					\
			    NULL,					\
			    &ws2812_gpio_##idx##_cfg, POST_KERNEL,	\
			    CONFIG_LED_STRIP_INIT_PRIORITY,		\
			    &ws2812_gpio_api);

DT_INST_FOREACH_STATUS_OKAY(WS2812_GPIO_DEVICE)