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

[kgunda@codeaurora.org]

On 2018-05-08 16:05, Daniel Thompson wrote:
> On Thu, May 03, 2018 at 03:42:30PM +0530, Kiran Gunda wrote:
>> 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
> 
> So we think a short report every quarter second is harmless?
> 
> 
Yes. We wait for the short to report 5 times with in this time. If the 
short
still persists, we go and disable the WLED module to avoid the damage. 
This is
suggested by the HW team.

>> +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,
> 
> NULL? There's no register we can check to make sure the interrupt
> handler did not enter spuriously?
> 
> 
There is FAULT_STATUS register. I will address it in the next series.

>> +				       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);
>> 
>> --
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
>> Forum,
>>  a Linux Foundation Collaborative Project
>>