leds: sc27xx: Add pattern_set/clear interfaces for LED controller

This patch implements the 'pattern_set'and 'pattern_clear'
interfaces to support SC27XX LED breathing mode.

Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Acked-by: Pavel Machek <pavel@ucw.c>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>

Documentation/ABI/testing/sysfs-class-led-driver-sc27xx

@@ -0,0 +1,22 @@
+What:		/sys/class/leds/<led>/hw_pattern
+Date:		September 2018
+KernelVersion:	4.20
+Description:
+		Specify a hardware pattern for the SC27XX LED. For the SC27XX
+		LED controller, it only supports 4 stages to make a single
+		hardware pattern, which is used to configure the rise time,
+		high time, fall time and low time for the breathing mode.
+
+		For the breathing mode, the SC27XX LED only expects one brightness
+		for the high stage. To be compatible with the hardware pattern
+		format, we should set brightness as 0 for rise stage, fall
+		stage and low stage.
+
+		Min stage duration: 125 ms
+		Max stage duration: 31875 ms
+
+		Since the stage duration step is 125 ms, the duration should be
+		a multiplier of 125, like 125ms, 250ms, 375ms, 500ms ... 31875ms.
+
+		Thus the format of the hardware pattern values should be:
+		"0 rise_duration brightness high_duration 0 fall_duration 0 low_duration".

drivers/leds/leds-sc27xx-bltc.c

@@ -32,8 +32,18 @@
 #define SC27XX_DUTY_MASK	GENMASK(15, 0)
 #define SC27XX_MOD_MASK		GENMASK(7, 0)
 
+#define SC27XX_CURVE_SHIFT	8
+#define SC27XX_CURVE_L_MASK	GENMASK(7, 0)
+#define SC27XX_CURVE_H_MASK	GENMASK(15, 8)
+
 #define SC27XX_LEDS_OFFSET	0x10
 #define SC27XX_LEDS_MAX		3
+#define SC27XX_LEDS_PATTERN_CNT	4
+/* Stage duration step, in milliseconds */
+#define SC27XX_LEDS_STEP	125
+/* Minimum and maximum duration, in milliseconds */
+#define SC27XX_DELTA_T_MIN	SC27XX_LEDS_STEP
+#define SC27XX_DELTA_T_MAX	(SC27XX_LEDS_STEP * 255)
 
 struct sc27xx_led {
 	char name[LED_MAX_NAME_SIZE];
@@ -122,6 +132,113 @@ static int sc27xx_led_set(struct led_classdev *ldev, enum led_brightness value)
 	return err;
 }
 
+static void sc27xx_led_clamp_align_delta_t(u32 *delta_t)
+{
+	u32 v, offset, t = *delta_t;
+
+	v = t + SC27XX_LEDS_STEP / 2;
+	v = clamp_t(u32, v, SC27XX_DELTA_T_MIN, SC27XX_DELTA_T_MAX);
+	offset = v - SC27XX_DELTA_T_MIN;
+	offset = SC27XX_LEDS_STEP * (offset / SC27XX_LEDS_STEP);
+
+	*delta_t = SC27XX_DELTA_T_MIN + offset;
+}
+
+static int sc27xx_led_pattern_clear(struct led_classdev *ldev)
+{
+	struct sc27xx_led *leds = to_sc27xx_led(ldev);
+	struct regmap *regmap = leds->priv->regmap;
+	u32 base = sc27xx_led_get_offset(leds);
+	u32 ctrl_base = leds->priv->base + SC27XX_LEDS_CTRL;
+	u8 ctrl_shift = SC27XX_CTRL_SHIFT * leds->line;
+	int err;
+
+	mutex_lock(&leds->priv->lock);
+
+	/* Reset the rise, high, fall and low time to zero. */
+	regmap_write(regmap, base + SC27XX_LEDS_CURVE0, 0);
+	regmap_write(regmap, base + SC27XX_LEDS_CURVE1, 0);
+
+	err = regmap_update_bits(regmap, ctrl_base,
+			(SC27XX_LED_RUN | SC27XX_LED_TYPE) << ctrl_shift, 0);
+
+	ldev->brightness = LED_OFF;
+
+	mutex_unlock(&leds->priv->lock);
+
+	return err;
+}
+
+static int sc27xx_led_pattern_set(struct led_classdev *ldev,
+				  struct led_pattern *pattern,
+				  u32 len, int repeat)
+{
+	struct sc27xx_led *leds = to_sc27xx_led(ldev);
+	u32 base = sc27xx_led_get_offset(leds);
+	u32 ctrl_base = leds->priv->base + SC27XX_LEDS_CTRL;
+	u8 ctrl_shift = SC27XX_CTRL_SHIFT * leds->line;
+	struct regmap *regmap = leds->priv->regmap;
+	int err;
+
+	/*
+	 * Must contain 4 tuples to configure the rise time, high time, fall
+	 * time and low time to enable the breathing mode.
+	 */
+	if (len != SC27XX_LEDS_PATTERN_CNT)
+		return -EINVAL;
+
+	mutex_lock(&leds->priv->lock);
+
+	sc27xx_led_clamp_align_delta_t(&pattern[0].delta_t);
+	err = regmap_update_bits(regmap, base + SC27XX_LEDS_CURVE0,
+				 SC27XX_CURVE_L_MASK,
+				 pattern[0].delta_t / SC27XX_LEDS_STEP);
+	if (err)
+		goto out;
+
+	sc27xx_led_clamp_align_delta_t(&pattern[1].delta_t);
+	err = regmap_update_bits(regmap, base + SC27XX_LEDS_CURVE1,
+				 SC27XX_CURVE_L_MASK,
+				 pattern[1].delta_t / SC27XX_LEDS_STEP);
+	if (err)
+		goto out;
+
+	sc27xx_led_clamp_align_delta_t(&pattern[2].delta_t);
+	err = regmap_update_bits(regmap, base + SC27XX_LEDS_CURVE0,
+				 SC27XX_CURVE_H_MASK,
+				 (pattern[2].delta_t / SC27XX_LEDS_STEP) <<
+				 SC27XX_CURVE_SHIFT);
+	if (err)
+		goto out;
+
+	sc27xx_led_clamp_align_delta_t(&pattern[3].delta_t);
+	err = regmap_update_bits(regmap, base + SC27XX_LEDS_CURVE1,
+				 SC27XX_CURVE_H_MASK,
+				 (pattern[3].delta_t / SC27XX_LEDS_STEP) <<
+				 SC27XX_CURVE_SHIFT);
+	if (err)
+		goto out;
+
+	err = regmap_update_bits(regmap, base + SC27XX_LEDS_DUTY,
+				 SC27XX_DUTY_MASK,
+				 (pattern[1].brightness << SC27XX_DUTY_SHIFT) |
+				 SC27XX_MOD_MASK);
+	if (err)
+		goto out;
+
+	/* Enable the LED breathing mode */
+	err = regmap_update_bits(regmap, ctrl_base,
+				 SC27XX_LED_RUN << ctrl_shift,
+				 SC27XX_LED_RUN << ctrl_shift);
+	if (!err)
+		ldev->brightness = pattern[1].brightness;
+
+out:
+	mutex_unlock(&leds->priv->lock);
+
+	return err;
+}
+
 static int sc27xx_led_register(struct device *dev, struct sc27xx_led_priv *priv)
 {
 	int i, err;
@@ -140,6 +257,9 @@ static int sc27xx_led_register(struct device *dev, struct sc27xx_led_priv *priv)
 		led->priv = priv;
 		led->ldev.name = led->name;
 		led->ldev.brightness_set_blocking = sc27xx_led_set;
+		led->ldev.pattern_set = sc27xx_led_pattern_set;
+		led->ldev.pattern_clear = sc27xx_led_pattern_clear;
+		led->ldev.default_trigger = "pattern";
 
 		err = devm_led_classdev_register(dev, &led->ldev);
 		if (err)
@@ -241,4 +361,5 @@ module_platform_driver(sc27xx_led_driver);
 
 MODULE_DESCRIPTION("Spreadtrum SC27xx breathing light controller driver");
 MODULE_AUTHOR("Xiaotong Lu <xiaotong.lu@spreadtrum.com>");
+MODULE_AUTHOR("Baolin Wang <baolin.wang@linaro.org>");
 MODULE_LICENSE("GPL v2");