leds: spi-byte: add single byte SPI LED driver

This driver adds support for simple SPI based LED controller which use
only one byte for setting the brightness.

Signed-off-by: Christian Mauderer <oss@c-mauderer.de>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>

3 files changed, 172 insertions, 0 deletions

diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index 71be87bdb926..35fcddb7ac2a 100644
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig
@@ -783,6 +783,16 @@ config LEDS_NIC78BX
           To compile this driver as a module, choose M here: the module
           will be called leds-nic78bx.
 
+config LEDS_SPI_BYTE
+        tristate "LED support for SPI LED controller with a single byte"
+        depends on LEDS_CLASS
+        depends on SPI
+        depends on OF
+        help
+          This option enables support for LED controller which use a single byte
+          for controlling the brightness. Currently the following controller is
+          supported: Ubiquiti airCube ISP microcontroller based LED controller.
+
 comment "LED Triggers"
 source "drivers/leds/trigger/Kconfig"
 
diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
index 1e9702ebffee..2e8bff590700 100644
--- a/drivers/leds/Makefile
+++ b/drivers/leds/Makefile
@@ -77,6 +77,7 @@ obj-$(CONFIG_LEDS_PM8058)		+= leds-pm8058.o
 obj-$(CONFIG_LEDS_MLXCPLD)              += leds-mlxcpld.o
 obj-$(CONFIG_LEDS_MLXREG)               += leds-mlxreg.o
 obj-$(CONFIG_LEDS_NIC78BX)              += leds-nic78bx.o
+obj-$(CONFIG_LEDS_SPI_BYTE)             += leds-spi-byte.o
 obj-$(CONFIG_LEDS_MT6323)               += leds-mt6323.o
 obj-$(CONFIG_LEDS_LM3692X)              += leds-lm3692x.o
 obj-$(CONFIG_LEDS_SC27XX_BLTC)          += leds-sc27xx-bltc.o
diff --git a/drivers/leds/leds-spi-byte.c b/drivers/leds/leds-spi-byte.c
new file mode 100644
index 000000000000..b231b563b7bb
--- /dev/null
+++ b/drivers/leds/leds-spi-byte.c
@@ -0,0 +1,161 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Christian Mauderer <oss@c-mauderer.de>
+
+/*
+ * The driver supports controllers with a very simple SPI protocol:
+ * - one LED is controlled by a single byte on MOSI
+ * - the value of the byte gives the brightness between two values (lowest to
+ *   highest)
+ * - no return value is necessary (no MISO signal)
+ *
+ * The value for minimum and maximum brightness depends on the device
+ * (compatible string).
+ *
+ * Supported devices:
+ * - "ubnt,acb-spi-led": Microcontroller (SONiX 8F26E611LA) based device used
+ *   for example in Ubiquiti airCube ISP. Reverse engineered protocol for this
+ *   controller:
+ *   * Higher two bits set a mode. Lower six bits are a parameter.
+ *   * Mode: 00 -> set brightness between 0x00 (min) and 0x3F (max)
+ *   * Mode: 01 -> pulsing pattern (min -> max -> min) with an interval. From
+ *     some tests, the period is about (50ms + 102ms * parameter). There is a
+ *     slightly different pattern starting from 0x10 (longer gap between the
+ *     pulses) but the time still follows that calculation.
+ *   * Mode: 10 -> same as 01 but with only a ramp from min to max. Again a
+ *     slight jump in the pattern at 0x10.
+ *   * Mode: 11 -> blinking (off -> 25% -> off -> 25% -> ...) with a period of
+ *     (105ms * parameter)
+ *   NOTE: This driver currently only supports mode 00.
+ */
+
+#include <linux/leds.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/spi/spi.h>
+#include <linux/mutex.h>
+#include <uapi/linux/uleds.h>
+
+struct spi_byte_chipdef {
+        /* SPI byte that will be send to switch the LED off */
+        u8      off_value;
+        /* SPI byte that will be send to switch the LED to maximum brightness */
+        u8      max_value;
+};
+
+struct spi_byte_led {
+        struct led_classdev             ldev;
+        struct spi_device               *spi;
+        char                            name[LED_MAX_NAME_SIZE];
+        struct mutex                    mutex;
+        const struct spi_byte_chipdef   *cdef;
+};
+
+static const struct spi_byte_chipdef ubnt_acb_spi_led_cdef = {
+        .off_value = 0x0,
+        .max_value = 0x3F,
+};
+
+static const struct of_device_id spi_byte_dt_ids[] = {
+        { .compatible = "ubnt,acb-spi-led", .data = &ubnt_acb_spi_led_cdef },
+        {},
+};
+
+MODULE_DEVICE_TABLE(of, spi_byte_dt_ids);
+
+static int spi_byte_brightness_set_blocking(struct led_classdev *dev,
+                                            enum led_brightness brightness)
+{
+        struct spi_byte_led *led = container_of(dev, struct spi_byte_led, ldev);
+        u8 value;
+        int ret;
+
+        value = (u8) brightness + led->cdef->off_value;
+
+        mutex_lock(&led->mutex);
+        ret = spi_write(led->spi, &value, sizeof(value));
+        mutex_unlock(&led->mutex);
+
+        return ret;
+}
+
+static int spi_byte_probe(struct spi_device *spi)
+{
+        const struct of_device_id *of_dev_id;
+        struct device_node *child;
+        struct device *dev = &spi->dev;
+        struct spi_byte_led *led;
+        const char *name = "leds-spi-byte::";
+        const char *state;
+        int ret;
+
+        of_dev_id = of_match_device(spi_byte_dt_ids, dev);
+        if (!of_dev_id)
+                return -EINVAL;
+
+        if (of_get_child_count(dev->of_node) != 1) {
+                dev_err(dev, "Device must have exactly one LED sub-node.");
+                return -EINVAL;
+        }
+        child = of_get_next_child(dev->of_node, NULL);
+
+        led = devm_kzalloc(dev, sizeof(*led), GFP_KERNEL);
+        if (!led)
+                return -ENOMEM;
+
+        of_property_read_string(child, "label", &name);
+        strlcpy(led->name, name, sizeof(led->name));
+        led->spi = spi;
+        mutex_init(&led->mutex);
+        led->cdef = of_dev_id->data;
+        led->ldev.name = led->name;
+        led->ldev.brightness = LED_OFF;
+        led->ldev.max_brightness = led->cdef->max_value - led->cdef->off_value;
+        led->ldev.brightness_set_blocking = spi_byte_brightness_set_blocking;
+
+        state = of_get_property(child, "default-state", NULL);
+        if (state) {
+                if (!strcmp(state, "on")) {
+                        led->ldev.brightness = led->ldev.max_brightness;
+                } else if (strcmp(state, "off")) {
+                        /* all other cases except "off" */
+                        dev_err(dev, "default-state can only be 'on' or 'off'");
+                        return -EINVAL;
+                }
+        }
+        spi_byte_brightness_set_blocking(&led->ldev,
+                                         led->ldev.brightness);
+
+        ret = devm_led_classdev_register(&spi->dev, &led->ldev);
+        if (ret) {
+                mutex_destroy(&led->mutex);
+                return ret;
+        }
+        spi_set_drvdata(spi, led);
+
+        return 0;
+}
+
+static int spi_byte_remove(struct spi_device *spi)
+{
+        struct spi_byte_led     *led = spi_get_drvdata(spi);
+
+        mutex_destroy(&led->mutex);
+
+        return 0;
+}
+
+static struct spi_driver spi_byte_driver = {
+        .probe          = spi_byte_probe,
+        .remove         = spi_byte_remove,
+        .driver = {
+                .name           = KBUILD_MODNAME,
+                .of_match_table = spi_byte_dt_ids,
+        },
+};
+
+module_spi_driver(spi_byte_driver);
+
+MODULE_AUTHOR("Christian Mauderer <oss@c-mauderer.de>");
+MODULE_DESCRIPTION("single byte SPI LED driver");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("spi:leds-spi-byte");