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Subject[PATCH v3 3/3] drivers: leds: add support for apa102c leds
Date
Initilial commit in order to support the apa102c RGB leds. The
RGB and global brightness management is done by creating 4 leds
from the Led Framework per apa102c led.

Signed-off-by: Nicolas Belin <nbelin@baylibre.com>
---
drivers/leds/Kconfig | 11 ++
drivers/leds/Makefile | 1 +
drivers/leds/leds-apa102c.c | 306 ++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 318 insertions(+)
create mode 100644 drivers/leds/leds-apa102c.c

diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index d82f1dea3711..28fa6c4f65cc 100644
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig
@@ -69,6 +69,17 @@ config LEDS_AN30259A
To compile this driver as a module, choose M here: the module
will be called leds-an30259a.

+config LEDS_APA102C
+ tristate "LED Support for Shiji APA102C"
+ depends on SPI
+ depends on LEDS_CLASS
+ help
+ This option enables support for the APA102C RGB LEDs
+ from Shiji Lighting.
+
+ To compile this driver as a module, choose M here: the module
+ will be called leds-apa102c.
+
config LEDS_APU
tristate "Front panel LED support for PC Engines APU/APU2/APU3 boards"
depends on LEDS_CLASS
diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
index d7e1107753fb..28dfe82900c5 100644
--- a/drivers/leds/Makefile
+++ b/drivers/leds/Makefile
@@ -88,6 +88,7 @@ obj-$(CONFIG_LEDS_LM36274) += leds-lm36274.o
obj-$(CONFIG_LEDS_TPS6105X) += leds-tps6105x.o

# LED SPI Drivers
+obj-$(CONFIG_LEDS_APA102C) += leds-apa102c.o
obj-$(CONFIG_LEDS_CR0014114) += leds-cr0014114.o
obj-$(CONFIG_LEDS_DAC124S085) += leds-dac124s085.o
obj-$(CONFIG_LEDS_EL15203000) += leds-el15203000.o
diff --git a/drivers/leds/leds-apa102c.c b/drivers/leds/leds-apa102c.c
new file mode 100644
index 000000000000..0043e7a6235b
--- /dev/null
+++ b/drivers/leds/leds-apa102c.c
@@ -0,0 +1,306 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/leds.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/spi/spi.h>
+#include <uapi/linux/uleds.h>
+#include "leds.h"
+
+/*
+ * Copyright (C) 2020 BayLibre, SAS
+ * Author: Nicolas Belin <nbelin@baylibre.com>
+ */
+
+/*
+ * APA102C SPI protocol description:
+ * +------+----------------------------------------+------+
+ * |START | DATA FIELD: | END |
+ * |FRAME | N LED FRAMES |FRAME |
+ * +------+------+------+------+------+-----+------+------+
+ * | 0*32 | LED1 | LED2 | LED3 | LED4 | --- | LEDN | 1*32 |
+ * +------+------+------+------+------+-----+------+------+
+ *
+ * +-----------------------------------+
+ * |START FRAME 32bits |
+ * +--------+--------+--------+--------+
+ * |00000000|00000000|00000000|00000000|
+ * +--------+--------+--------+--------+
+ *
+ * +------------------------------------+
+ * |LED FRAME 32bits |
+ * +---+-----+--------+--------+--------+
+ * |111|LUMA | BLUE | GREEN | RED |
+ * +---+-----+--------+--------+--------+
+ * |3b |5bits| 8bits | 8bits | 8bits |
+ * +---+-----+--------+--------+--------+
+ * |MSB LSB|MSB LSB|MSB LSB|MSB LSB|
+ * +---+-----+--------+--------+--------+
+ *
+ * +-----------------------------------+
+ * |END FRAME 32bits |
+ * +--------+--------+--------+--------+
+ * |11111111|11111111|11111111|11111111|
+ * +--------+--------+--------+--------+
+ */
+
+/* apa102c default settings */
+#define GLOBAL_MAX_BRIGHTNESS GENMASK(4, 0)
+#define RGB_MAX_BRIGHTNESS GENMASK(7, 0)
+#define START_BYTE 0
+#define END_BYTE GENMASK(7, 0)
+#define LED_FRAME_HEADER GENMASK(7, 5)
+
+struct apa102c_led {
+ struct apa102c *priv;
+ char name[LED_MAX_NAME_SIZE];
+ int color_id;
+ struct led_classdev cdev;
+};
+
+struct apa102c_rgbled {
+ /* the 4 components of the apa102c rgb led:
+ * global brightness, blue, green and red in that order
+ */
+ struct apa102c_led component[4];
+};
+
+struct apa102c {
+ size_t led_count;
+ struct device *dev;
+ struct mutex lock;
+ struct spi_device *spi;
+ u8 *spi_buf;
+ struct apa102c_rgbled rgb_leds[];
+};
+
+static int apa102c_sync(struct apa102c *priv)
+{
+ int ret;
+ size_t i;
+ struct apa102c_rgbled *leds = priv->rgb_leds;
+ u8 *buf = priv->spi_buf;
+
+ /* creating the data that will be sent to all the leds at once */
+ for (i = 0; i < 4; i++)
+ *buf++ = START_BYTE;
+
+ /* looping on each RGB led component, getting the global brightness
+ * then B, G and R values
+ */
+ for (i = 0; i < priv->led_count; i++) {
+ *buf++ = LED_FRAME_HEADER |
+ leds[i].component[0].cdev.brightness;
+ *buf++ = leds[i].component[1].cdev.brightness;
+ *buf++ = leds[i].component[2].cdev.brightness;
+ *buf++ = leds[i].component[3].cdev.brightness;
+ }
+
+ for (i = 0; i < 4; i++)
+ *buf++ = END_BYTE;
+
+ ret = spi_write(priv->spi, priv->spi_buf,
+ (priv->led_count + 2) * sizeof(u32));
+
+ return ret;
+}
+
+static int apa102c_brightness_set(struct led_classdev *cdev,
+ enum led_brightness brightness)
+{
+ int ret;
+ struct apa102c_led *led = container_of(cdev,
+ struct apa102c_led,
+ cdev);
+
+ mutex_lock(&led->priv->lock);
+ /* updating the brightness then synching all the leds */
+ cdev->brightness = brightness;
+ ret = apa102c_sync(led->priv);
+ mutex_unlock(&led->priv->lock);
+
+ return ret;
+}
+
+static int apa102c_probe_dt(struct apa102c *priv)
+{
+ int ret = 0;
+ u32 i;
+ struct apa102c_rgbled *rgb_led;
+ struct apa102c_led *led;
+ struct fwnode_handle *child;
+ const char *rgb_led_name;
+ const char *led_component_name;
+
+ /* each node corresponds to an rgb led */
+ device_for_each_child_node(priv->dev, child) {
+
+ ret = fwnode_property_read_u32(child, "reg", &i);
+ if (ret) {
+ dev_err(priv->dev, "coudld not read reg %d\n", ret);
+ goto child_out;
+ }
+
+ if (i >= priv->led_count) {
+ ret = -EINVAL;
+ dev_err(priv->dev, "reg value too big\n");
+ goto child_out;
+ }
+
+ rgb_led = &priv->rgb_leds[i];
+ /* checking if this led config is already used by checking if
+ * the priv member of the global_brightness led as already
+ * been set
+ */
+ if (rgb_led->component[0].priv) {
+ ret = -EINVAL;
+ dev_err(priv->dev, "using the same reg value twice\n");
+ goto child_out;
+ }
+
+ ret = fwnode_property_read_string(child, "label",
+ &rgb_led_name);
+ if (ret) {
+ ret = -EINVAL;
+ dev_err(priv->dev, "missing rgb led name\n");
+ goto child_out;
+ }
+
+ /* setting a color_id value for each of the 4 components of the
+ * apa102c RGB led. The first component is the global brightness
+ * of the led and thus has no color. The order of the colors
+ * after the global brightness is then blue, green and red
+ * in that order. It corresponds to the order in which the
+ * values are sent using spi
+ */
+ rgb_led->component[0].color_id = -1; //no color
+ rgb_led->component[1].color_id = LED_COLOR_ID_BLUE;
+ rgb_led->component[2].color_id = LED_COLOR_ID_GREEN;
+ rgb_led->component[3].color_id = LED_COLOR_ID_RED;
+
+ /* now looping on each component and registering a corresponding
+ * led
+ */
+ for (i = 0; i < 4; i++) {
+ led = &rgb_led->component[i];
+ if (led->color_id == -1) {
+ /* the global brightness has no defined name
+ * so setting it to "brightness". It also has
+ * a different MAX_BRIGHTNESS value.
+ * If a trigger is present, setting it on this
+ * component
+ */
+ led->cdev.max_brightness =
+ GLOBAL_MAX_BRIGHTNESS;
+ led_component_name = "brightness";
+ fwnode_property_read_string(child,
+ "linux,default-trigger",
+ &led->cdev.default_trigger);
+ } else {
+ /* using the color name defined by the framework
+ * for the B, G and R components
+ */
+ led->cdev.max_brightness = RGB_MAX_BRIGHTNESS;
+ led_component_name = led_colors[led->color_id];
+ }
+
+ /* the rest is common to all the components */
+ led->priv = priv;
+ led->cdev.brightness_set_blocking =
+ apa102c_brightness_set;
+ /* creating our own led name to differentiate the 4
+ * components
+ */
+ snprintf(led->name, sizeof(led->name),
+ "%s_%s", rgb_led_name, led_component_name);
+ led->cdev.name = led->name;
+
+ ret = devm_led_classdev_register_ext(priv->dev,
+ &led->cdev,
+ NULL);
+ if (ret) {
+ dev_err(priv->dev, "led register err: %d\n",
+ ret);
+ goto child_out;
+ }
+ }
+ }
+
+child_out:
+ return ret;
+}
+
+static int apa102c_probe(struct spi_device *spi)
+{
+ struct apa102c *priv;
+ size_t led_count;
+ int ret;
+
+ led_count = device_get_child_node_count(&spi->dev);
+ if (!led_count) {
+ dev_err(&spi->dev, "No LEDs defined in device tree!");
+ return -ENODEV;
+ }
+
+ priv = devm_kzalloc(&spi->dev,
+ struct_size(priv, rgb_leds, led_count),
+ GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ priv->spi_buf = devm_kzalloc(&spi->dev,
+ (led_count + 2) * sizeof(u32),
+ GFP_KERNEL);
+ if (!priv->spi_buf)
+ return -ENOMEM;
+
+ mutex_init(&priv->lock);
+ priv->led_count = led_count;
+ priv->dev = &spi->dev;
+ priv->spi = spi;
+
+ ret = apa102c_probe_dt(priv);
+ if (ret)
+ return ret;
+
+ /* Set the LEDs with default values at start */
+ apa102c_sync(priv);
+ if (ret)
+ return ret;
+
+ spi_set_drvdata(spi, priv);
+
+ return 0;
+}
+
+static int apa102c_remove(struct spi_device *spi)
+{
+ struct apa102c *priv = spi_get_drvdata(spi);
+
+ mutex_destroy(&priv->lock);
+
+ return 0;
+}
+
+static const struct of_device_id apa102c_dt_ids[] = {
+ { .compatible = "shiji,apa102c", },
+ {},
+};
+
+MODULE_DEVICE_TABLE(of, apa102c_dt_ids);
+
+static struct spi_driver apa102c_driver = {
+ .probe = apa102c_probe,
+ .remove = apa102c_remove,
+ .driver = {
+ .name = KBUILD_MODNAME,
+ .of_match_table = apa102c_dt_ids,
+ },
+};
+
+module_spi_driver(apa102c_driver);
+
+MODULE_AUTHOR("Nicolas Belin <nbelin@baylibre.com>");
+MODULE_DESCRIPTION("apa102c LED driver");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("spi:apa102c");
--
2.7.4
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