Re: [PATCH V3 7/7] backlight: qcom-wled: Add auto string detection logic

[Bjorn Andersson]

On Tue 19 Jun 04:13 PDT 2018, Kiran Gunda wrote:

> The auto string detection algorithm checks if the current WLED
> sink configuration is valid. It tries enabling every sink and
> checks if the OVP fault is observed. Based on this information
> it detects and enables the valid sink configuration.
> Auto calibration will be triggered when the OVP fault interrupts
> are seen frequently thereby it tries to fix the sink configuration.
> 
> The auto-detection also kicks in when the connected LED string
> of the display-backlight malfunctions (because of damage) and
> requires the damaged string to be turned off to prevent the
> complete panel and/or board from being damaged.
> 
> Signed-off-by: Kiran Gunda <kgunda@xxxxxxxxxxxxxx>
> ---
>  drivers/video/backlight/qcom-wled.c | 408 +++++++++++++++++++++++++++++++++++-
>  1 file changed, 403 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/qcom-wled.c
> index e87ba70..6bc627c 100644
> --- a/drivers/video/backlight/qcom-wled.c
> +++ b/drivers/video/backlight/qcom-wled.c
> @@ -25,13 +25,23 @@
>  #define WLED_MAX_STRINGS				4
>  
>  #define WLED_DEFAULT_BRIGHTNESS				2048
> -
> +#define WLED_SOFT_START_DLY_US				10000
>  #define WLED3_SINK_REG_BRIGHT_MAX			0xFFF
>  
>  /* WLED3 control registers */
> +#define WLED3_CTRL_REG_FAULT_STATUS			0x08
> +#define  WLED3_CTRL_REG_ILIM_FAULT_BIT			BIT(0)
> +#define  WLED3_CTRL_REG_OVP_FAULT_BIT			BIT(1)
> +#define  WLED4_CTRL_REG_SC_FAULT_BIT			BIT(2)
> +
> +#define WLED3_CTRL_REG_INT_RT_STS			0x10
> +#define  WLED3_CTRL_REG_OVP_FAULT_STATUS		BIT(1)
> +

These seems to be used in both WLED 3 and 4, so please drop the 3 from
the name.

>  #define WLED3_CTRL_REG_MOD_EN				0x46
>  #define  WLED3_CTRL_REG_MOD_EN_MASK			BIT(7)
>  
> +#define WLED3_CTRL_REG_FEEDBACK_CONTROL			0x48
> +
>  #define WLED3_CTRL_REG_FREQ				0x4c
>  #define  WLED3_CTRL_REG_FREQ_MASK			GENMASK(3, 0)
>  
> @@ -146,6 +156,7 @@ struct wled_config {
>  	bool ext_gen;
>  	bool cabc;
>  	bool external_pfet;
> +	bool auto_detection_enabled;
>  };
>  
>  struct wled {
> @@ -154,16 +165,22 @@ struct wled {
>  	struct regmap *regmap;
>  	struct mutex lock;	/* Lock to avoid race from ISR */
>  	ktime_t last_short_event;
> +	ktime_t start_ovp_fault_time;
>  	u16 ctrl_addr;
>  	u16 sink_addr;
> +	u16 auto_detection_ovp_count;
>  	u32 brightness;
>  	u32 max_brightness;
>  	u32 short_count;
> +	u32 auto_detect_count;
>  	const int *version;
>  	bool disabled_by_short;
>  	bool has_short_detect;
> +	int ovp_irq;
> +	bool ovp_irq_disabled;
>  
>  	struct wled_config cfg;
> +	struct delayed_work ovp_work;
>  	int (*wled_set_brightness)(struct wled *wled, u16 brightness);
>  	int (*wled_sync_toggle)(struct wled *wled);
>  };
> @@ -209,6 +226,27 @@ static int wled4_set_brightness(struct wled *wled, u16 brightness)
>  	return 0;
>  }
>  
> +static void wled_ovp_work(struct work_struct *work)
> +{
> +	u32 val;
> +	int rc;
> +
> +	struct wled *wled = container_of(work,
> +					 struct wled, ovp_work.work);
> +
> +	rc = regmap_read(wled->regmap, wled->ctrl_addr + WLED3_CTRL_REG_MOD_EN,
> +			 &val);
> +	if (rc < 0)
> +		return;
> +
> +	if (val & WLED3_CTRL_REG_MOD_EN_MASK) {

The way you implement this now makes this a "delayed enable_irq" worker,
as such you shouldn't need to check if the hardware is enabled here but
just blindly enable_irq() and then in module_enable() you can check the
return value of cancel_delayed_work() to know if enable_irq() has been
called.

> +		if (wled->ovp_irq > 0 && wled->ovp_irq_disabled) {
> +			enable_irq(wled->ovp_irq);
> +			wled->ovp_irq_disabled = false;
> +		}
> +	}
> +}
> +
>  static int wled_module_enable(struct wled *wled, int val)
>  {
>  	int rc;
> @@ -220,7 +258,20 @@ static int wled_module_enable(struct wled *wled, int val)
>  				WLED3_CTRL_REG_MOD_EN,
>  				WLED3_CTRL_REG_MOD_EN_MASK,
>  				WLED3_CTRL_REG_MOD_EN_MASK);
> -	return rc;
> +	if (rc < 0)
> +		return rc;
> +
> +	if (val) {
> +		schedule_delayed_work(&wled->ovp_work, WLED_SOFT_START_DLY_US);
> +	} else {
> +		cancel_delayed_work(&wled->ovp_work);

I recommend using cancel_delayed_work_sync() to ensure that htis isn't
racing with the worker.

> +		if (wled->ovp_irq > 0 && !wled->ovp_irq_disabled) {
> +			disable_irq(wled->ovp_irq);
> +			wled->ovp_irq_disabled = true;
> +		}
> +	}
> +
> +	return 0;
>  }
>  
>  static int wled3_sync_toggle(struct wled *wled)
> @@ -346,6 +397,305 @@ static irqreturn_t wled_short_irq_handler(int irq, void *_wled)
>  	return IRQ_HANDLED;
>  }
>  
> +#define AUTO_DETECT_BRIGHTNESS		200
> +static int wled_auto_string_detection(struct wled *wled)

You don't care about the return value of this function in any of the
callers.

> +{
> +	int rc = 0, i;
> +	u32 sink_config = 0, int_sts;
> +	u8 sink_test = 0, sink_valid = 0, val;
> +
> +	/* read configured sink configuration */
> +	rc = regmap_read(wled->regmap, wled->sink_addr +
> +			 WLED4_SINK_REG_CURR_SINK, &sink_config);
> +	if (rc < 0) {
> +		pr_err("Failed to read SINK configuration rc=%d\n", rc);
> +		goto failed_detect;
> +	}
> +
> +	/* disable the module before starting detection */
> +	rc = regmap_update_bits(wled->regmap,
> +				wled->ctrl_addr + WLED3_CTRL_REG_MOD_EN,
> +				WLED3_CTRL_REG_MOD_EN_MASK, 0);
> +	if (rc < 0) {
> +		pr_err("Failed to disable WLED module rc=%d\n", rc);
> +		goto failed_detect;
> +	}
> +
> +	/* set low brightness across all sinks */
> +	rc = wled4_set_brightness(wled, AUTO_DETECT_BRIGHTNESS);
> +	if (rc < 0) {
> +		pr_err("Failed to set brightness for auto detection rc=%d\n",
> +		       rc);
> +		goto failed_detect;
> +	}
> +
> +	if (wled->cfg.cabc) {
> +		for (i = 0; i < wled->cfg.num_strings; i++) {
> +			rc = regmap_update_bits(wled->regmap, wled->sink_addr +
> +						WLED4_SINK_REG_STR_CABC(i),
> +						WLED4_SINK_REG_STR_CABC_MASK,
> +						0);
> +			if (rc < 0)
> +				goto failed_detect;
> +		}
> +	}
> +
> +	/* disable all sinks */
> +	rc = regmap_write(wled->regmap,
> +			  wled->sink_addr + WLED4_SINK_REG_CURR_SINK, 0);
> +	if (rc < 0) {
> +		pr_err("Failed to disable all sinks rc=%d\n", rc);
> +		goto failed_detect;
> +	}
> +
> +	/* iterate through the strings one by one */
> +	for (i = 0; i < wled->cfg.num_strings; i++) {
> +		sink_test = BIT((WLED4_SINK_REG_CURR_SINK_SHFT + i));
> +
> +		/* Enable feedback control */
> +		rc = regmap_write(wled->regmap, wled->ctrl_addr +
> +				  WLED3_CTRL_REG_FEEDBACK_CONTROL, i + 1);
> +		if (rc < 0) {
> +			pr_err("Failed to enable feedback for SINK %d rc = %d\n",
> +			       i + 1, rc);
> +			goto failed_detect;
> +		}
> +
> +		/* enable the sink */
> +		rc = regmap_write(wled->regmap, wled->sink_addr +
> +				  WLED4_SINK_REG_CURR_SINK, sink_test);
> +		if (rc < 0) {
> +			pr_err("Failed to configure SINK %d rc=%d\n", i + 1,
> +			       rc);
> +			goto failed_detect;
> +		}
> +
> +		/* Enable the module */
> +		rc = regmap_update_bits(wled->regmap, wled->ctrl_addr +
> +					WLED3_CTRL_REG_MOD_EN,
> +					WLED3_CTRL_REG_MOD_EN_MASK,
> +					WLED3_CTRL_REG_MOD_EN_MASK);
> +		if (rc < 0) {
> +			pr_err("Failed to enable WLED module rc=%d\n", rc);
> +			goto failed_detect;
> +		}
> +
> +		usleep_range(WLED_SOFT_START_DLY_US,
> +			     WLED_SOFT_START_DLY_US + 1000);
> +
> +		rc = regmap_read(wled->regmap, wled->ctrl_addr +
> +				 WLED3_CTRL_REG_INT_RT_STS, &int_sts);
> +		if (rc < 0) {
> +			pr_err("Error in reading WLED3_CTRL_INT_RT_STS rc=%d\n",
> +			       rc);

You should probably do something about the state of the hardware if it
fail here.

> +			goto failed_detect;
> +		}
> +
> +		if (int_sts & WLED3_CTRL_REG_OVP_FAULT_STATUS)
> +			pr_debug("WLED OVP fault detected with SINK %d\n",
> +				 i + 1);
> +		else
> +			sink_valid |= sink_test;
> +
> +		/* Disable the module */
> +		rc = regmap_update_bits(wled->regmap,
> +					wled->ctrl_addr + WLED3_CTRL_REG_MOD_EN,
> +					WLED3_CTRL_REG_MOD_EN_MASK, 0);
> +		if (rc < 0) {
> +			pr_err("Failed to disable WLED module rc=%d\n", rc);
> +			goto failed_detect;
> +		}
> +	}
> +
> +	if (sink_valid == sink_config) {
> +		pr_debug("WLED auto-detection complete, default sink-config=%x OK!\n",
> +			 sink_config);

It's not the "default" sink config we're using, it's whatever was
configured before this function was called.

> +	} else {
> +		pr_warn("Invalid WLED default sink config=%x changing it to=%x\n",

Use dev_warn(), and as it's not the "default sink config" that's invalid
write something like "New WLED string configuration found: %x". Perhaps
you can print it using %*pbl ? 

> +			sink_config, sink_valid);
> +		sink_config = sink_valid;
> +	}
> +
> +	if (!sink_config) {
> +		pr_err("No valid WLED sinks found\n");

dev_err() and move this above the other prints, there's no reason to
first say that you found an "invalid WLED default" and then say that you
didn't findd a valid config.

> +		wled->disabled_by_short = true;
> +		goto failed_detect;
> +	}
> +
> +	/* write the new sink configuration */
> +	rc = regmap_write(wled->regmap,
> +			  wled->sink_addr + WLED4_SINK_REG_CURR_SINK,
> +			  sink_config);
> +	if (rc < 0) {
> +		pr_err("Failed to reconfigure the default sink rc=%d\n", rc);
> +		goto failed_detect;
> +	}
> +
> +	/* Enable valid sinks */
> +	for (i = 0; i < wled->cfg.num_strings; i++) {
> +		if (wled->cfg.cabc) {
> +			rc = regmap_update_bits(wled->regmap, wled->sink_addr +
> +						WLED4_SINK_REG_STR_CABC(i),
> +						WLED4_SINK_REG_STR_CABC_MASK,
> +						WLED4_SINK_REG_STR_CABC_MASK);
> +			if (rc < 0)
> +				goto failed_detect;
> +		}
> +
> +		if (sink_config & BIT(WLED4_SINK_REG_CURR_SINK_SHFT + i))
> +			val = WLED4_SINK_REG_STR_MOD_MASK;
> +		else
> +			val = 0x0; /* disable modulator_en for unused sink */
> +
> +		rc = regmap_write(wled->regmap, wled->sink_addr +
> +				  WLED4_SINK_REG_STR_MOD_EN(i), val);
> +		if (rc < 0) {
> +			pr_err("Failed to configure MODULATOR_EN rc=%d\n", rc);
> +			goto failed_detect;
> +		}
> +	}
> +
> +	/* restore the feedback setting */
> +	rc = regmap_write(wled->regmap,
> +			  wled->ctrl_addr + WLED3_CTRL_REG_FEEDBACK_CONTROL, 0);
> +	if (rc < 0) {
> +		pr_err("Failed to restore feedback setting rc=%d\n", rc);
> +		goto failed_detect;
> +	}
> +
> +	/* restore  brightness */

Extra space

> +	rc = wled4_set_brightness(wled, wled->brightness);
> +	if (rc < 0) {
> +		pr_err("Failed to set brightness after auto detection rc=%d\n",
> +		       rc);
> +		goto failed_detect;
> +	}
> +
> +	rc = regmap_update_bits(wled->regmap,
> +				wled->ctrl_addr + WLED3_CTRL_REG_MOD_EN,
> +				WLED3_CTRL_REG_MOD_EN_MASK,
> +				WLED3_CTRL_REG_MOD_EN_MASK);
> +	if (rc < 0) {
> +		pr_err("Failed to enable WLED module rc=%d\n", rc);
> +		goto failed_detect;
> +	}
> +
> +failed_detect:
> +	return rc;
> +}
> +
> +#define WLED_AUTO_DETECT_OVP_COUNT		5
> +#define WLED_AUTO_DETECT_CNT_DLY_US		USEC_PER_SEC
> +static bool wled_auto_detection_required(struct wled *wled)
> +{
> +	s64 elapsed_time_us;
> +
> +	if (*wled->version == WLED_PM8941 || !wled->cfg.auto_detection_enabled)

Ensure that auto_detection_enabled can't be enabled for pm8941, so that
you don't need to check the first part.

> +		return false;
> +
> +	/*
> +	 * Check if the OVP fault was an occasional one
> +	 * or if it's firing continuously, the latter qualifies
> +	 * for an auto-detection check.
> +	 */
> +	if (!wled->auto_detection_ovp_count) {
> +		wled->start_ovp_fault_time = ktime_get();
> +		wled->auto_detection_ovp_count++;
> +	} else {
> +		elapsed_time_us = ktime_us_delta(ktime_get(),
> +						 wled->start_ovp_fault_time);
> +		if (elapsed_time_us > WLED_AUTO_DETECT_CNT_DLY_US)
> +			wled->auto_detection_ovp_count = 0;
> +		else
> +			wled->auto_detection_ovp_count++;
> +
> +		if (wled->auto_detection_ovp_count >=
> +				WLED_AUTO_DETECT_OVP_COUNT) {
> +			wled->auto_detection_ovp_count = 0;
> +			return true;
> +		}
> +	}
> +
> +	return false;
> +}
> +
> +static int wled_auto_detection_at_init(struct wled *wled)
> +{
> +	int rc;
> +	u32 fault_status = 0, rt_status = 0;

No need to initialize these, they will be filled out if regmap_read
return successfully.

> +
> +	if (!wled->cfg.auto_detection_enabled)
> +		return 0;
> +
[..]
> @@ -836,6 +1192,42 @@ static int wled_configure_short_irq(struct wled *wled,
>  	return rc;
>  }
>  
> +static int wled_configure_ovp_irq(struct wled *wled,
> +				  struct platform_device *pdev)
> +{
> +	int rc = 0;

No need to initialize rc here.

> +	u32 val;
> +
> +	wled->ovp_irq = platform_get_irq_byname(pdev, "ovp");
> +	if (wled->ovp_irq < 0) {
> +		dev_dbg(&pdev->dev, "ovp irq is not used\n");
> +		return 0;
> +	}
> +
> +	rc = devm_request_threaded_irq(wled->dev, wled->ovp_irq, NULL,
> +				       wled_ovp_irq_handler, IRQF_ONESHOT,
> +				       "wled_ovp_irq", wled);
> +	if (rc < 0) {
> +		dev_err(wled->dev, "Unable to request ovp_irq (err:%d)\n",
> +			rc);
> +		wled->ovp_irq = 0;
> +		return 0;
> +	}
> +
> +	rc = regmap_read(wled->regmap, wled->ctrl_addr +
> +			 WLED3_CTRL_REG_MOD_EN, &val);
> +	if (rc < 0)
> +		return rc;
> +
> +	/* Keep OVP irq disabled until module is enabled */
> +	if (!rc && !(val & WLED3_CTRL_REG_MOD_EN_MASK)) {

If rc isn't 0 we returned above.

> +		disable_irq(wled->ovp_irq);
> +		wled->ovp_irq_disabled = true;
> +	}
> +
> +	return rc;

As such, it is always 0 here.

> +}
> +

Regards,
Bjorn