diff options
Diffstat (limited to 'package/kernel/leds-ws2812b/src/leds-ws2812b.c')
| -rw-r--r-- | package/kernel/leds-ws2812b/src/leds-ws2812b.c | 233 |
1 files changed, 233 insertions, 0 deletions
diff --git a/package/kernel/leds-ws2812b/src/leds-ws2812b.c b/package/kernel/leds-ws2812b/src/leds-ws2812b.c new file mode 100644 index 0000000000..b0d13f5242 --- /dev/null +++ b/package/kernel/leds-ws2812b/src/leds-ws2812b.c @@ -0,0 +1,233 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * WorldSemi WS2812B individually-addressable LED driver using SPI + * + * Copyright 2022 Chuanhong Guo <gch981213@gmail.com> + * + * This driver simulates WS2812B protocol using SPI MOSI pin. A one pulse + * is transferred as 3'b110 and a zero pulse is 3'b100. For this driver to + * work properly, the SPI frequency should be 2.105MHz~2.85MHz and it needs + * to transfer all the bytes continuously. + */ + +#include <linux/led-class-multicolor.h> +#include <linux/leds.h> +#include <linux/module.h> +#include <linux/of_device.h> +#include <linux/property.h> +#include <linux/spi/spi.h> +#include <linux/mutex.h> + +#define WS2812B_BYTES_PER_COLOR 3 +#define WS2812B_NUM_COLORS 3 +/* A continuous 0 for 50us+ as the 'reset' signal */ +#define WS2812B_RESET_LEN 18 + +struct ws2812b_led { + struct led_classdev_mc mc_cdev; + struct mc_subled subled[WS2812B_NUM_COLORS]; + int cascade; +}; + +struct ws2812b_priv { + struct led_classdev ldev; + struct spi_device *spi; + struct mutex mutex; + int num_leds; + size_t data_len; + u8 *data_buf; + struct ws2812b_led leds[]; +}; + +/** + * ws2812b_set_byte - convert a byte of data to 3-byte SPI data for pulses + * @priv: pointer to the private data structure + * @offset: offset of the target byte in the data stream + * @val: 1-byte data to be set + * + * WS2812B receives a stream of bytes from DI, takes the first 3 byte as LED + * brightness and pases the rest to the next LED through the DO pin. + * This function assembles a single byte of data to the LED: + * A bit is represented with a pulse of specific length. A long pulse is a 1 + * and a short pulse is a 0. + * SPI transfers data continuously, MSB first. We can send 3'b100 to create a + * 0 pulse and 3'b110 for a 1 pulse. In this way, a byte of data takes up 3 + * bytes in a SPI transfer: + * 1x0 1x0 1x0 1x0 1x0 1x0 1x0 1x0 + * Let's rearrange it in 8 bits: + * 1x01x01x 01x01x01 x01x01x0 + * The higher 3 bits, middle 2 bits and lower 3 bits are represented with the + * 1st, 2nd and 3rd byte in the SPI transfer respectively. + * There are only 8 combinations for 3 bits and 4 for 2 bits, so we can create + * a lookup table for the 3 bytes. + * e.g. For 0x6b -> 2'b01101011: + * Bit 7-5: 3'b011 -> 10011011 -> 0x9b + * Bit 4-3: 2'b01 -> 01001101 -> 0x4d + * Bit 2-0: 3'b011 -> 00110110 -> 0x36 + */ +static void ws2812b_set_byte(struct ws2812b_priv *priv, size_t offset, u8 val) +{ + /* The lookup table for Bit 7-5 4-3 2-0 */ + const u8 h3b[] = { 0x92, 0x93, 0x9a, 0x9b, 0xd2, 0xd3, 0xda, 0xdb }; + const u8 m2b[] = { 0x49, 0x4d, 0x69, 0x6d }; + const u8 l3b[] = { 0x24, 0x26, 0x34, 0x36, 0xa4, 0xa6, 0xb4, 0xb6 }; + u8 *p = priv->data_buf + WS2812B_RESET_LEN + (offset * WS2812B_BYTES_PER_COLOR); + + p[0] = h3b[val >> 5]; /* Bit 7-5 */ + p[1] = m2b[(val >> 3) & 0x3]; /* Bit 4-3 */ + p[2] = l3b[val & 0x7]; /* Bit 2-0 */ +} + +static int ws2812b_set(struct led_classdev *cdev, + enum led_brightness brightness) +{ + struct led_classdev_mc *mc_cdev = lcdev_to_mccdev(cdev); + struct ws2812b_led *led = + container_of(mc_cdev, struct ws2812b_led, mc_cdev); + struct ws2812b_priv *priv = dev_get_drvdata(cdev->dev->parent); + int ret; + int i; + + led_mc_calc_color_components(mc_cdev, brightness); + + mutex_lock(&priv->mutex); + for (i = 0; i < WS2812B_NUM_COLORS; i++) + ws2812b_set_byte(priv, led->cascade * WS2812B_NUM_COLORS + i, + led->subled[i].brightness); + ret = spi_write(priv->spi, priv->data_buf, priv->data_len); + mutex_unlock(&priv->mutex); + + return ret; +} + +static int ws2812b_probe(struct spi_device *spi) +{ + struct device *dev = &spi->dev; + int cur_led = 0; + struct ws2812b_priv *priv; + struct fwnode_handle *led_node; + int num_leds, i, cnt, ret; + + num_leds = device_get_child_node_count(dev); + + priv = devm_kzalloc(dev, struct_size(priv, leds, num_leds), GFP_KERNEL); + if (!priv) + return -ENOMEM; + priv->data_len = + num_leds * WS2812B_BYTES_PER_COLOR * WS2812B_NUM_COLORS + + WS2812B_RESET_LEN; + priv->data_buf = kzalloc(priv->data_len, GFP_KERNEL); + if (!priv->data_buf) + return -ENOMEM; + + for (i = 0; i < num_leds * WS2812B_NUM_COLORS; i++) + ws2812b_set_byte(priv, i, 0); + + mutex_init(&priv->mutex); + priv->num_leds = num_leds; + priv->spi = spi; + + device_for_each_child_node(dev, led_node) { + struct led_init_data init_data = { + .fwnode = led_node, + }; + /* WS2812B LEDs usually come with GRB color */ + u32 color_idx[WS2812B_NUM_COLORS] = { + LED_COLOR_ID_GREEN, + LED_COLOR_ID_RED, + LED_COLOR_ID_BLUE, + }; + u32 cascade; + + ret = fwnode_property_read_u32(led_node, "reg", &cascade); + if (ret) { + dev_err(dev, "failed to obtain numerical LED index for %s", + fwnode_get_name(led_node)); + goto ERR_UNREG_LEDS; + } + if (cascade >= num_leds) { + dev_err(dev, "LED index of %s is larger than the number of LEDs.", + fwnode_get_name(led_node)); + ret = -EINVAL; + goto ERR_UNREG_LEDS; + } + + cnt = fwnode_property_count_u32(led_node, "color-index"); + if (cnt > 0 && cnt <= WS2812B_NUM_COLORS) + fwnode_property_read_u32_array(led_node, "color-index", + color_idx, (size_t)cnt); + + priv->leds[cur_led].mc_cdev.subled_info = + priv->leds[cur_led].subled; + priv->leds[cur_led].mc_cdev.num_colors = WS2812B_NUM_COLORS; + priv->leds[cur_led].mc_cdev.led_cdev.max_brightness = 255; + priv->leds[cur_led].mc_cdev.led_cdev.brightness_set_blocking = ws2812b_set; + + for (i = 0; i < WS2812B_NUM_COLORS; i++) { + priv->leds[cur_led].subled[i].color_index = color_idx[i]; + priv->leds[cur_led].subled[i].intensity = 255; + } + + priv->leds[cur_led].cascade = cascade; + + ret = led_classdev_multicolor_register_ext( + dev, &priv->leds[cur_led].mc_cdev, &init_data); + if (ret) { + dev_err(dev, "registration of %s failed.", + fwnode_get_name(led_node)); + goto ERR_UNREG_LEDS; + } + cur_led++; + } + + spi_set_drvdata(spi, priv); + + return 0; +ERR_UNREG_LEDS: + for (; cur_led >= 0; cur_led--) + led_classdev_multicolor_unregister(&priv->leds[cur_led].mc_cdev); + mutex_destroy(&priv->mutex); + kfree(priv->data_buf); + return ret; +} + +static int ws2812b_remove(struct spi_device *spi) +{ + struct ws2812b_priv *priv = spi_get_drvdata(spi); + int cur_led; + + for (cur_led = priv->num_leds - 1; cur_led >= 0; cur_led--) + led_classdev_multicolor_unregister(&priv->leds[cur_led].mc_cdev); + kfree(priv->data_buf); + mutex_destroy(&priv->mutex); + + return 0; +} + +static const struct spi_device_id ws2812b_spi_ids[] = { + { "ws2812b" }, + {}, +}; +MODULE_DEVICE_TABLE(spi, ws2812b_spi_ids); + +static const struct of_device_id ws2812b_dt_ids[] = { + { .compatible = "worldsemi,ws2812b" }, + {}, +}; +MODULE_DEVICE_TABLE(of, ws2812b_dt_ids); + +static struct spi_driver ws2812b_driver = { + .probe = ws2812b_probe, + .remove = ws2812b_remove, + .id_table = ws2812b_spi_ids, + .driver = { + .name = KBUILD_MODNAME, + .of_match_table = ws2812b_dt_ids, + }, +}; + +module_spi_driver(ws2812b_driver); + +MODULE_AUTHOR("Chuanhong Guo <gch981213@gmail.com>"); +MODULE_DESCRIPTION("WS2812B LED driver using SPI"); +MODULE_LICENSE("GPL"); |