backlight: qcom-wled: Add support for short circuit handling

Handle the short circuit interrupt and check if the short circuit
interrupt is valid. Re-enable the module to check if it goes
away. Disable the module altogether if the short circuit event
persists.
Signed-off-by: Kiran Gunda <kgunda@codeaurora.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/video/backlight/qcom-wled.c

@@ -2,6 +2,9 @@
 /* Copyright (c) 2015, Sony Mobile Communications, AB.
  */
 
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/ktime.h>
 #include <linux/kernel.h>
 #include <linux/backlight.h>
 #include <linux/module.h>
@@ -56,6 +59,16 @@
 #define WLED3_SINK_REG_STR_CABC(n)			(0x66 + (n * 0x10))
 #define  WLED3_SINK_REG_STR_CABC_MASK			BIT(7)
 
+/* WLED4 specific control registers */
+#define WLED4_CTRL_REG_SHORT_PROTECT			0x5e
+#define  WLED4_CTRL_REG_SHORT_EN_MASK			BIT(7)
+
+#define WLED4_CTRL_REG_SEC_ACCESS			0xd0
+#define  WLED4_CTRL_REG_SEC_UNLOCK			0xa5
+
+#define WLED4_CTRL_REG_TEST1				0xe2
+#define  WLED4_CTRL_REG_TEST1_EXT_FET_DTEST2		0x09
+
 /* WLED4 specific sink registers */
 #define WLED4_SINK_REG_CURR_SINK			0x46
 #define  WLED4_SINK_REG_CURR_SINK_MASK			GENMASK(7, 4)
@@ -105,17 +118,24 @@ struct wled_config {
 	bool cs_out_en;
 	bool ext_gen;
 	bool cabc;
+	bool external_pfet;
 };
 
 struct wled {
 	const char *name;
 	struct device *dev;
 	struct regmap *regmap;
+	struct mutex lock;	/* Lock to avoid race from thread irq handler */
+	ktime_t last_short_event;
 	u16 ctrl_addr;
 	u16 sink_addr;
 	u16 max_string_count;
 	u32 brightness;
 	u32 max_brightness;
+	u32 short_count;
+	bool disabled_by_short;
+	bool has_short_detect;
+	int short_irq;
 
 	struct wled_config cfg;
 	int (*wled_set_brightness)(struct wled *wled, u16 brightness);
@@ -166,6 +186,9 @@ static int wled_module_enable(struct wled *wled, int val)
 {
 	int rc;
 
+	if (wled->disabled_by_short)
+		return -ENXIO;
+
 	rc = regmap_update_bits(wled->regmap, wled->ctrl_addr +
 				WLED3_CTRL_REG_MOD_EN,
 				WLED3_CTRL_REG_MOD_EN_MASK,
@@ -202,18 +225,19 @@ static int wled_update_status(struct backlight_device *bl)
 	    bl->props.state & BL_CORE_FBBLANK)
 		brightness = 0;
 
+	mutex_lock(&wled->lock);
 	if (brightness) {
 		rc = wled->wled_set_brightness(wled, brightness);
 		if (rc < 0) {
 			dev_err(wled->dev, "wled failed to set brightness rc:%d\n",
 				rc);
-			return rc;
+			goto unlock_mutex;
 		}
 
 		rc = wled_sync_toggle(wled);
 		if (rc < 0) {
 			dev_err(wled->dev, "wled sync failed rc:%d\n", rc);
-			return rc;
+			goto unlock_mutex;
 		}
 	}
 
@@ -221,15 +245,61 @@ static int wled_update_status(struct backlight_device *bl)
 		rc = wled_module_enable(wled, !!brightness);
 		if (rc < 0) {
 			dev_err(wled->dev, "wled enable failed rc:%d\n", rc);
-			return rc;
+			goto unlock_mutex;
 		}
 	}
 
 	wled->brightness = brightness;
 
+unlock_mutex:
+	mutex_unlock(&wled->lock);
+
 	return rc;
 }
 
+#define WLED_SHORT_DLY_MS			20
+#define WLED_SHORT_CNT_MAX			5
+#define WLED_SHORT_RESET_CNT_DLY_US		USEC_PER_SEC
+
+static irqreturn_t wled_short_irq_handler(int irq, void *_wled)
+{
+	struct wled *wled = _wled;
+	int rc;
+	s64 elapsed_time;
+
+	wled->short_count++;
+	mutex_lock(&wled->lock);
+	rc = wled_module_enable(wled, false);
+	if (rc < 0) {
+		dev_err(wled->dev, "wled disable failed rc:%d\n", rc);
+		goto unlock_mutex;
+	}
+
+	elapsed_time = ktime_us_delta(ktime_get(),
+				      wled->last_short_event);
+	if (elapsed_time > WLED_SHORT_RESET_CNT_DLY_US)
+		wled->short_count = 1;
+
+	if (wled->short_count > WLED_SHORT_CNT_MAX) {
+		dev_err(wled->dev, "Short trigged %d times, disabling WLED forever!\n",
+			wled->short_count);
+		wled->disabled_by_short = true;
+		goto unlock_mutex;
+	}
+
+	wled->last_short_event = ktime_get();
+
+	msleep(WLED_SHORT_DLY_MS);
+	rc = wled_module_enable(wled, true);
+	if (rc < 0)
+		dev_err(wled->dev, "wled enable failed rc:%d\n", rc);
+
+unlock_mutex:
+	mutex_unlock(&wled->lock);
+
+	return IRQ_HANDLED;
+}
+
 static int wled3_setup(struct wled *wled)
 {
 	u16 addr;
@@ -318,7 +388,7 @@ static int wled4_setup(struct wled *wled)
 	int rc, temp, i, j;
 	u16 addr;
 	u8 sink_en = 0;
-	u32 sink_cfg = 0;
+	u32 sink_cfg;
 
 	rc = regmap_update_bits(wled->regmap,
 				wled->ctrl_addr + WLED3_CTRL_REG_OVP,
@@ -340,6 +410,21 @@ static int wled4_setup(struct wled *wled)
 	if (rc < 0)
 		return rc;
 
+	if (wled->cfg.external_pfet) {
+		/* Unlock the secure register access */
+		rc = regmap_write(wled->regmap, wled->ctrl_addr +
+				  WLED4_CTRL_REG_SEC_ACCESS,
+				  WLED4_CTRL_REG_SEC_UNLOCK);
+		if (rc < 0)
+			return rc;
+
+		rc = regmap_write(wled->regmap,
+				  wled->ctrl_addr + WLED4_CTRL_REG_TEST1,
+				  WLED4_CTRL_REG_TEST1_EXT_FET_DTEST2);
+		if (rc < 0)
+			return rc;
+	}
+
 	rc = regmap_read(wled->regmap, wled->sink_addr +
 			 WLED4_SINK_REG_CURR_SINK, &sink_cfg);
 	if (rc < 0)
@@ -425,6 +510,7 @@ static const struct wled_config wled4_config_defaults = {
 	.num_strings = 4,
 	.switch_freq = 11,
 	.cabc = false,
+	.external_pfet = false,
 };
 
 static const u32 wled3_boost_i_limit_values[] = {
@@ -590,6 +676,7 @@ static int wled_configure(struct wled *wled, int version)
 		{ "qcom,cs-out", &cfg->cs_out_en, },
 		{ "qcom,ext-gen", &cfg->ext_gen, },
 		{ "qcom,cabc", &cfg->cabc, },
+		{ "qcom,external-pfet", &cfg->external_pfet, },
 	};
 
 	prop_addr = of_get_address(dev->of_node, 0, NULL, NULL);
@@ -678,6 +765,38 @@ static int wled_configure(struct wled *wled, int version)
 	return 0;
 }
 
+static int wled_configure_short_irq(struct wled *wled,
+				    struct platform_device *pdev)
+{
+	int rc;
+
+	if (!wled->has_short_detect)
+		return 0;
+
+	rc = regmap_update_bits(wled->regmap, wled->ctrl_addr +
+				WLED4_CTRL_REG_SHORT_PROTECT,
+				WLED4_CTRL_REG_SHORT_EN_MASK,
+				WLED4_CTRL_REG_SHORT_EN_MASK);
+	if (rc < 0)
+		return rc;
+
+	wled->short_irq = platform_get_irq_byname(pdev, "short");
+	if (wled->short_irq < 0) {
+		dev_dbg(&pdev->dev, "short irq is not used\n");
+		return 0;
+	}
+
+	rc = devm_request_threaded_irq(wled->dev, wled->short_irq,
+				       NULL, wled_short_irq_handler,
+				       IRQF_ONESHOT,
+				       "wled_short_irq", wled);
+	if (rc < 0)
+		dev_err(wled->dev, "Unable to request short_irq (err:%d)\n",
+			rc);
+
+	return rc;
+}
+
 static const struct backlight_ops wled_ops = {
 	.update_status = wled_update_status,
 };
@@ -711,6 +830,7 @@ static int wled_probe(struct platform_device *pdev)
 		return -ENODEV;
 	}
 
+	mutex_init(&wled->lock);
 	rc = wled_configure(wled, version);
 	if (rc)
 		return rc;
@@ -725,6 +845,7 @@ static int wled_probe(struct platform_device *pdev)
 		break;
 
 	case 4:
+		wled->has_short_detect = true;
 		rc = wled4_setup(wled);
 		if (rc) {
 			dev_err(&pdev->dev, "wled4_setup failed\n");
@@ -737,6 +858,10 @@ static int wled_probe(struct platform_device *pdev)
 		break;
 	}
 
+	rc = wled_configure_short_irq(wled, pdev);
+	if (rc < 0)
+		return rc;
+
 	val = WLED_DEFAULT_BRIGHTNESS;
 	of_property_read_u32(pdev->dev.of_node, "default-brightness", &val);
 
@@ -750,6 +875,16 @@ static int wled_probe(struct platform_device *pdev)
 	return PTR_ERR_OR_ZERO(bl);
 };
 
+static int wled_remove(struct platform_device *pdev)
+{
+	struct wled *wled = dev_get_drvdata(&pdev->dev);
+
+	mutex_destroy(&wled->lock);
+	disable_irq(wled->short_irq);
+
+	return 0;
+}
+
 static const struct of_device_id wled_match_table[] = {
 	{ .compatible = "qcom,pm8941-wled", .data = (void *)3 },
 	{ .compatible = "qcom,pmi8998-wled", .data = (void *)4 },
@@ -760,6 +895,7 @@ MODULE_DEVICE_TABLE(of, wled_match_table);
 
 static struct platform_driver wled_driver = {
 	.probe = wled_probe,
+	.remove = wled_remove,
 	.driver	= {
 		.name = "qcom,wled",
 		.of_match_table	= wled_match_table,