--- /dev/null
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Backlight driver for the Kinetic KTD253
+ * Based on code and know-how from the Samsung GT-S7710
+ * Gareth Phillips <gareth.phillips@samsung.com>
+ */
+#include <linux/backlight.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/fb.h>
+#include <linux/gpio/consumer.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/limits.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/slab.h>
+
+/* Current ratio is n/32 from 1/32 to 32/32 */
+#define KTD253_MIN_RATIO 1
+#define KTD253_MAX_RATIO 32
+#define KTD253_DEFAULT_RATIO 13
+
+#define KTD253_T_LOW_NS (200 + 10) /* Additional 10ns as safety factor */
+#define KTD253_T_HIGH_NS (200 + 10) /* Additional 10ns as safety factor */
+#define KTD253_T_OFF_MS 3
+
+struct ktd253_backlight {
+ struct device *dev;
+ struct backlight_device *bl;
+ struct gpio_desc *gpiod;
+ u16 ratio;
+};
+
+static int ktd253_backlight_update_status(struct backlight_device *bl)
+{
+ struct ktd253_backlight *ktd253 = bl_get_data(bl);
+ int brightness = backlight_get_brightness(bl);
+ u16 target_ratio;
+ u16 current_ratio = ktd253->ratio;
+ unsigned long flags;
+
+ dev_dbg(ktd253->dev, "new brightness/ratio: %d/32\n", brightness);
+
+ target_ratio = brightness;
+
+ if (target_ratio == current_ratio)
+ /* This is already right */
+ return 0;
+
+ if (target_ratio == 0) {
+ gpiod_set_value_cansleep(ktd253->gpiod, 0);
+ /*
+ * We need to keep the GPIO low for at least this long
+ * to actually switch the KTD253 off.
+ */
+ msleep(KTD253_T_OFF_MS);
+ ktd253->ratio = 0;
+ return 0;
+ }
+
+ if (current_ratio == 0) {
+ gpiod_set_value_cansleep(ktd253->gpiod, 1);
+ ndelay(KTD253_T_HIGH_NS);
+ /* We always fall back to this when we power on */
+ current_ratio = KTD253_MAX_RATIO;
+ }
+
+ /*
+ * WARNING:
+ * The loop to set the correct current level is performed
+ * with interrupts disabled as it is timing critical.
+ * The maximum number of cycles of the loop is 32
+ * so the time taken will be (T_LOW_NS + T_HIGH_NS + loop_time) * 32,
+ */
+ local_irq_save(flags);
+ while (current_ratio != target_ratio) {
+ /*
+ * These GPIO operations absolutely can NOT sleep so no
+ * _cansleep suffixes, and no using GPIO expanders on
+ * slow buses for this!
+ */
+ gpiod_set_value(ktd253->gpiod, 0);
+ ndelay(KTD253_T_LOW_NS);
+ gpiod_set_value(ktd253->gpiod, 1);
+ ndelay(KTD253_T_HIGH_NS);
+ /* After 1/32 we loop back to 32/32 */
+ if (current_ratio == KTD253_MIN_RATIO)
+ current_ratio = KTD253_MAX_RATIO;
+ else
+ current_ratio--;
+ }
+ local_irq_restore(flags);
+ ktd253->ratio = current_ratio;
+
+ dev_dbg(ktd253->dev, "new ratio set to %d/32\n", target_ratio);
+
+ return 0;
+}
+
+static const struct backlight_ops ktd253_backlight_ops = {
+ .options = BL_CORE_SUSPENDRESUME,
+ .update_status = ktd253_backlight_update_status,
+};
+
+static int ktd253_backlight_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct backlight_device *bl;
+ struct ktd253_backlight *ktd253;
+ u32 max_brightness;
+ u32 brightness;
+ int ret;
+
+ ktd253 = devm_kzalloc(dev, sizeof(*ktd253), GFP_KERNEL);
+ if (!ktd253)
+ return -ENOMEM;
+ ktd253->dev = dev;
+
+ ret = device_property_read_u32(dev, "max-brightness", &max_brightness);
+ if (ret)
+ max_brightness = KTD253_MAX_RATIO;
+ if (max_brightness > KTD253_MAX_RATIO) {
+ /* Clamp brightness to hardware max */
+ dev_err(dev, "illegal max brightness specified\n");
+ max_brightness = KTD253_MAX_RATIO;
+ }
+
+ ret = device_property_read_u32(dev, "default-brightness", &brightness);
+ if (ret)
+ brightness = KTD253_DEFAULT_RATIO;
+ if (brightness > max_brightness) {
+ /* Clamp default brightness to max brightness */
+ dev_err(dev, "default brightness exceeds max brightness\n");
+ brightness = max_brightness;
+ }
+
+ if (brightness)
+ /* This will be the default ratio when the KTD253 is enabled */
+ ktd253->ratio = KTD253_MAX_RATIO;
+ else
+ ktd253->ratio = 0;
+
+ ktd253->gpiod = devm_gpiod_get(dev, "enable",
+ brightness ? GPIOD_OUT_HIGH :
+ GPIOD_OUT_LOW);
+ if (IS_ERR(ktd253->gpiod)) {
+ ret = PTR_ERR(ktd253->gpiod);
+ if (ret != -EPROBE_DEFER)
+ dev_err(dev, "gpio line missing or invalid.\n");
+ return ret;
+ }
+ gpiod_set_consumer_name(ktd253->gpiod, dev_name(dev));
+
+ bl = devm_backlight_device_register(dev, dev_name(dev), dev, ktd253,
+ &ktd253_backlight_ops, NULL);
+ if (IS_ERR(bl)) {
+ dev_err(dev, "failed to register backlight\n");
+ return PTR_ERR(bl);
+ }
+ bl->props.max_brightness = max_brightness;
+ /* When we just enable the GPIO line we set max brightness */
+ if (brightness) {
+ bl->props.brightness = brightness;
+ bl->props.power = FB_BLANK_UNBLANK;
+ } else {
+ bl->props.brightness = 0;
+ bl->props.power = FB_BLANK_POWERDOWN;
+ }
+
+ ktd253->bl = bl;
+ platform_set_drvdata(pdev, bl);
+ backlight_update_status(bl);
+
+ return 0;
+}
+
+static const struct of_device_id ktd253_backlight_of_match[] = {
+ { .compatible = "kinetic,ktd253" },
+ { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, ktd253_backlight_of_match);
+
+static struct platform_driver ktd253_backlight_driver = {
+ .driver = {
+ .name = "ktd253-backlight",
+ .of_match_table = ktd253_backlight_of_match,
+ },
+ .probe = ktd253_backlight_probe,
+};
+module_platform_driver(ktd253_backlight_driver);
+
+MODULE_AUTHOR("Linus Walleij <linus.walleij@linaro.org>");
+MODULE_DESCRIPTION("Kinetic KTD253 Backlight Driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:ktd253-backlight");
git.samba.org / sfrench / cifs-2.6.git / commitdiff