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Date:   Thu, 17 Oct 2019 13:26:53 +0100
From:   Lee Jones <lee.jones@linaro.org>
To:     Kiran Gunda <kgunda@codeaurora.org>
Cc:     bjorn.andersson@linaro.org, jingoohan1@gmail.com,
        b.zolnierkie@samsung.com, dri-devel@lists.freedesktop.org,
        daniel.thompson@linaro.org, jacek.anaszewski@gmail.com,
        pavel@ucw.cz, robh+dt@kernel.org, mark.rutland@arm.com,
        linux-leds@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, Andy Gross <agross@kernel.org>,
        linux-arm-msm@vger.kernel.org, linux-fbdev@vger.kernel.org
Subject: Re: [PATCH V7 6/6] backlight: qcom-wled: Add auto string detection
 logic
Message-ID: <20191017122653.GO4365@dell>
References: <1571220826-7740-1-git-send-email-kgunda@codeaurora.org>
 <1571220826-7740-7-git-send-email-kgunda@codeaurora.org>
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On Wed, 16 Oct 2019, 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@codeaurora.org>
> ---
>  drivers/video/backlight/qcom-wled.c | 410 +++++++++++++++++++++++++++++++++++-
>  1 file changed, 404 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/qcom-wled.c
> index b5b125c..ff7c409 100644
> --- a/drivers/video/backlight/qcom-wled.c
> +++ b/drivers/video/backlight/qcom-wled.c


[...]

> +	/* iterate through the strings one by one */

Please use proper English in comments (less a full stop).

In this case, just s/iterate/Iterate/.

> +	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) {
> +			dev_err(wled->dev, "Failed to enable feedback for SINK %d rc = %d\n",
> +				i + 1, rc);
> +			goto failed_detect;
> +		}
> +
> +		/* enable the sink */

Here too.  And everywhere else.

> +		rc = regmap_write(wled->regmap, wled->sink_addr +
> +				  WLED4_SINK_REG_CURR_SINK, sink_test);
> +		if (rc < 0) {
> +			dev_err(wled->dev, "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) {
> +			dev_err(wled->dev, "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) {
> +			dev_err(wled->dev, "Error in reading WLED3_CTRL_INT_RT_STS rc=%d\n",
> +				rc);
> +			goto failed_detect;
> +		}
> +
> +		if (int_sts & WLED3_CTRL_REG_OVP_FAULT_STATUS)
> +			dev_dbg(wled->dev, "WLED OVP fault detected with SINK %d\n",
> +				i + 1);

I haven't reviewed the whole patch, but this caught my eye.

I think this should be upgraded to dev_warn().

> +		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) {
> +			dev_err(wled->dev, "Failed to disable WLED module rc=%d\n",
> +				rc);
> +			goto failed_detect;
> +		}
> +	}
> +
> +	if (!sink_valid) {
> +		dev_err(wled->dev, "No valid WLED sinks found\n");
> +		wled->disabled_by_short = true;
> +		goto failed_detect;
> +	}
> +
> +	if (sink_valid == sink_config) {
> +		dev_dbg(wled->dev, "WLED auto-detection complete, sink-config=%x OK!\n",
> +			sink_config);

Does this really need to be placed in the kernel log?

> +	} else {
> +		dev_warn(wled->dev, "New WLED string configuration found %x\n",
> +			 sink_valid);

Why would the user care about this?  Is it not normal?

> +		sink_config = sink_valid;
> +	}

[...]

> +static irqreturn_t wled_ovp_irq_handler(int irq, void *_wled)
> +{
> +	struct wled *wled = _wled;
> +	int rc;
> +	u32 int_sts, fault_sts;
> +
> +	rc = regmap_read(wled->regmap,
> +			 wled->ctrl_addr + WLED3_CTRL_REG_INT_RT_STS, &int_sts);
> +	if (rc < 0) {
> +		dev_err(wled->dev, "Error in reading WLED3_INT_RT_STS rc=%d\n",
> +			rc);
> +		return IRQ_HANDLED;
> +	}
> +
> +	rc = regmap_read(wled->regmap, wled->ctrl_addr +
> +			 WLED3_CTRL_REG_FAULT_STATUS, &fault_sts);
> +	if (rc < 0) {
> +		dev_err(wled->dev, "Error in reading WLED_FAULT_STATUS rc=%d\n",
> +			rc);
> +		return IRQ_HANDLED;
> +	}
> +
> +	if (fault_sts &
> +		(WLED3_CTRL_REG_OVP_FAULT_BIT | WLED3_CTRL_REG_ILIM_FAULT_BIT))

Break the line at the '|'.

> +		dev_dbg(wled->dev, "WLED OVP fault detected, int_sts=%x fault_sts= %x\n",
> +			int_sts, fault_sts);

dev_warn().

> +	if (fault_sts & WLED3_CTRL_REG_OVP_FAULT_BIT) {
> +		mutex_lock(&wled->lock);
> +		disable_irq_nosync(wled->ovp_irq);
> +
> +		if (wled_auto_detection_required(wled))
> +			wled_auto_string_detection(wled);
> +
> +		enable_irq(wled->ovp_irq);
> +
> +		mutex_unlock(&wled->lock);
> +	}
> +
> +	return IRQ_HANDLED;
> +}
> +
>  static int wled3_setup(struct wled *wled)
>  {
>  	u16 addr;
> @@ -435,8 +775,10 @@ static int wled4_setup(struct wled *wled)
>  		sink_en |= 1 << temp;
>  	}
>  
> -	if (sink_cfg == sink_en)
> -		return 0;
> +	if (sink_cfg == sink_en) {
> +		rc = wled_auto_detection_at_init(wled);
> +		return rc;
> +	}
>  
>  	rc = regmap_update_bits(wled->regmap,
>  				wled->sink_addr + WLED4_SINK_REG_CURR_SINK,
> @@ -499,7 +841,9 @@ static int wled4_setup(struct wled *wled)
>  		return rc;
>  	}
>  
> -	return 0;
> +	rc = wled_auto_detection_at_init(wled);
> +
> +	return rc;
>  }
>  
>  static const struct wled_config wled4_config_defaults = {
> @@ -510,6 +854,7 @@ static int wled4_setup(struct wled *wled)
>  	.switch_freq = 11,
>  	.cabc = false,
>  	.external_pfet = false,
> +	.auto_detection_enabled = false,
>  };
>  
>  static const u32 wled3_boost_i_limit_values[] = {
> @@ -676,6 +1021,7 @@ static int wled_configure(struct wled *wled, int version)
>  		{ "qcom,ext-gen", &cfg->ext_gen, },
>  		{ "qcom,cabc", &cfg->cabc, },
>  		{ "qcom,external-pfet", &cfg->external_pfet, },
> +		{ "qcom,auto-string-detection", &cfg->auto_detection_enabled, },
>  	};
>  
>  	prop_addr = of_get_address(dev->of_node, 0, NULL, NULL);
> @@ -796,6 +1142,40 @@ 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;
> +	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");

I assume this is optional.  What happens if no IRQ is provided?

If, for instance, polling mode is enabled, maybe something like this
would be better?

      dev_warn(&pdev->dev, "No IRQ found, falling back to polling mode\n");

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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