[PATCH V2 3/5] backlight: qcom-wled: Add support for short circuit handling

[Kiran Gunda <kgunda@codeaurora.org>]

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>
---
 drivers/video/backlight/qcom-wled.c | 134 ++++++++++++++++++++++++++++++++++--
 1 file changed, 130 insertions(+), 4 deletions(-)

diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/qcom-wled.c
index be8b8d3..2cfba77 100644
--- a/drivers/video/backlight/qcom-wled.c
+++ b/drivers/video/backlight/qcom-wled.c
@@ -10,6 +10,9 @@
  * GNU General Public License for more details.
  */
 
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/ktime.h>
 #include <linux/kernel.h>
 #include <linux/backlight.h>
 #include <linux/module.h>
@@ -23,7 +26,9 @@
 
 #define WLED3_SINK_REG_BRIGHT_MAX			0xFFF
 
-/* Control registers */
+/* WLED3 Control registers */
+#define WLED3_CTRL_REG_FAULT_STATUS			0x08
+
 #define WLED3_CTRL_REG_MOD_EN				0x46
 #define  WLED3_CTRL_REG_MOD_EN_MASK			BIT(7)
 
@@ -36,7 +41,17 @@
 #define WLED3_CTRL_REG_ILIMIT				0x4e
 #define  WLED3_CTRL_REG_ILIMIT_MASK			GENMASK(2, 0)
 
-/* sink registers */
+/* WLED4 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
+
+/* WLED3 sink registers */
 #define WLED3_SINK_REG_SYNC				0x47
 #define  WLED3_SINK_REG_SYNC_MASK			GENMASK(2, 0)
 #define  WLED4_SINK_REG_SYNC_MASK			GENMASK(3, 0)
@@ -130,17 +145,23 @@ 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 ISR */
+	ktime_t last_short_event;
 	u16 ctrl_addr;
 	u16 sink_addr;
 	u32 brightness;
 	u32 max_brightness;
+	u32 short_count;
 	const int *version;
+	int short_irq;
+	bool force_mod_disable;
 
 	struct wled_config cfg;
 	int (*wled_set_brightness)(struct wled *wled, u16 brightness);
@@ -192,6 +213,9 @@ static int wled_module_enable(struct wled *wled, int val)
 {
 	int rc;
 
+	if (wled->force_mod_disable)
+		return 0;
+
 	rc = regmap_update_bits(wled->regmap, wled->ctrl_addr +
 				WLED3_CTRL_REG_MOD_EN,
 				WLED3_CTRL_REG_MOD_EN_MASK,
@@ -248,12 +272,13 @@ 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->wled_sync_toggle(wled);
@@ -267,15 +292,60 @@ 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	HZ
+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 = 0;
+
+	if (wled->short_count > WLED_SHORT_CNT_MAX) {
+		dev_err(wled->dev, "Short trigged %d times, disabling WLED forever!\n",
+			wled->short_count);
+		wled->force_mod_disable = 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;
@@ -435,6 +505,21 @@ static int wled4_setup(struct wled *wled)
 		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;
+	}
+
 	return 0;
 }
 
@@ -446,6 +531,7 @@ static int wled4_setup(struct wled *wled)
 	.switch_freq = 11,
 	.enabled_strings = 0xf,
 	.cabc = false,
+	.external_pfet = true,
 };
 
 static const u32 wled3_boost_i_limit_values[] = {
@@ -628,6 +714,7 @@ static int wled_configure(struct wled *wled)
 		{ "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);
@@ -701,6 +788,39 @@ static int wled_configure(struct wled *wled)
 	return 0;
 }
 
+static int wled_configure_short_irq(struct wled *wled,
+				    struct platform_device *pdev)
+{
+	int rc = 0;
+
+	/* PM8941 doesn't have the short detection support */
+	if (*wled->version == WLED_PM8941)
+		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,
 };
@@ -733,6 +853,8 @@ static int wled_probe(struct platform_device *pdev)
 		return -ENODEV;
 	}
 
+	mutex_init(&wled->lock);
+
 	rc = wled_configure(wled);
 	if (rc)
 		return rc;
@@ -752,6 +874,10 @@ static int wled_probe(struct platform_device *pdev)
 		}
 	}
 
+	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);
 
-- 
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