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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
commitace9429bb58fd418f0c81d4c2835699bddf6bde6 (patch)
treeb2d64bc10158fdd5497876388cd68142ca374ed3 /drivers/video/backlight/ktd253-backlight.c
parentInitial commit. (diff)
downloadlinux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.tar.xz
linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.zip
Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'drivers/video/backlight/ktd253-backlight.c')
-rw-r--r--drivers/video/backlight/ktd253-backlight.c225
1 files changed, 225 insertions, 0 deletions
diff --git a/drivers/video/backlight/ktd253-backlight.c b/drivers/video/backlight/ktd253-backlight.c
new file mode 100644
index 0000000000..d7d43454f6
--- /dev/null
+++ b/drivers/video/backlight/ktd253-backlight.c
@@ -0,0 +1,225 @@
+// 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_CRIT_NS 100000 /* 100 us, now it doesn't look good */
+#define KTD253_T_OFF_MS 3
+
+struct ktd253_backlight {
+ struct device *dev;
+ struct backlight_device *bl;
+ struct gpio_desc *gpiod;
+ u16 ratio;
+};
+
+static void ktd253_backlight_set_max_ratio(struct ktd253_backlight *ktd253)
+{
+ gpiod_set_value_cansleep(ktd253->gpiod, 1);
+ ndelay(KTD253_T_HIGH_NS);
+ /* We always fall back to this when we power on */
+}
+
+static int ktd253_backlight_stepdown(struct ktd253_backlight *ktd253)
+{
+ /*
+ * These GPIO operations absolutely can NOT sleep so no _cansleep
+ * suffixes, and no using GPIO expanders on slow buses for this!
+ *
+ * The maximum number of cycles of the loop is 32 so the time taken
+ * should nominally be:
+ * (T_LOW_NS + T_HIGH_NS + loop_time) * 32
+ *
+ * Architectures do not always support ndelay() and we will get a few us
+ * instead. If we get to a critical time limit an interrupt has likely
+ * occured in the low part of the loop and we need to restart from the
+ * top so we have the backlight in a known state.
+ */
+ u64 ns;
+
+ ns = ktime_get_ns();
+ gpiod_set_value(ktd253->gpiod, 0);
+ ndelay(KTD253_T_LOW_NS);
+ gpiod_set_value(ktd253->gpiod, 1);
+ ns = ktime_get_ns() - ns;
+ if (ns >= KTD253_T_OFF_CRIT_NS) {
+ dev_err(ktd253->dev, "PCM on backlight took too long (%llu ns)\n", ns);
+ return -EAGAIN;
+ }
+ ndelay(KTD253_T_HIGH_NS);
+ return 0;
+}
+
+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;
+ int ret;
+
+ 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) {
+ ktd253_backlight_set_max_ratio(ktd253);
+ current_ratio = KTD253_MAX_RATIO;
+ }
+
+ 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!
+ */
+ ret = ktd253_backlight_stepdown(ktd253);
+ if (ret == -EAGAIN) {
+ /*
+ * Something disturbed the backlight setting code when
+ * running so we need to bring the PWM back to a known
+ * state. This shouldn't happen too much.
+ */
+ gpiod_set_value_cansleep(ktd253->gpiod, 0);
+ msleep(KTD253_T_OFF_MS);
+ ktd253_backlight_set_max_ratio(ktd253);
+ current_ratio = KTD253_MAX_RATIO;
+ } else if (current_ratio == KTD253_MIN_RATIO) {
+ /* After 1/32 we loop back to 32/32 */
+ current_ratio = KTD253_MAX_RATIO;
+ } else {
+ current_ratio--;
+ }
+ }
+ 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;
+ }
+
+ ktd253->gpiod = devm_gpiod_get(dev, "enable", GPIOD_OUT_LOW);
+ if (IS_ERR(ktd253->gpiod))
+ return dev_err_probe(dev, PTR_ERR(ktd253->gpiod),
+ "gpio line missing or invalid.\n");
+ gpiod_set_consumer_name(ktd253->gpiod, dev_name(dev));
+ /* Bring backlight to a known off state */
+ msleep(KTD253_T_OFF_MS);
+
+ 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" },
+ { .compatible = "kinetic,ktd259" },
+ { /* 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");