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Date:   Tue, 8 May 2018 11:39:44 +0100
From:   Daniel Thompson <daniel.thompson@linaro.org>
To:     Kiran Gunda <kgunda@codeaurora.org>
Cc:     bjorn.andersson@linaro.org, Lee Jones <lee.jones@linaro.org>,
        Jingoo Han <jingoohan1@gmail.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org,
        linux-leds@vger.kernel.org
Subject: Re: [PATCH V2 4/5] backlight: qcom-wled: Add support for OVP
 interrupt handling
Message-ID: <20180508103944.qib7ax3sgzhzacmb@holly.lan>
References: <1525342352-25072-1-git-send-email-kgunda@codeaurora.org>
 <1525342352-25072-5-git-send-email-kgunda@codeaurora.org>
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On Thu, May 03, 2018 at 03:42:31PM +0530, Kiran Gunda wrote:
> WLED peripheral has over voltage protection(OVP) circuitry and the OVP
> fault is notified through an interrupt. Though this fault condition rising
> is due to an incorrect hardware configuration is mitigated in the hardware,
> it still needs to be detected and handled. Add support for it.

Why detect and handle it? The interrupt handler doesn't appear to do
anything other than clear the interrupt... and it appears that the 
interrupt can be masked.


> When WLED module is enabled, keep OVP fault interrupt disabled for 10 ms to
> account for soft start delay.
> 
> Signed-off-by: Kiran Gunda <kgunda@codeaurora.org>
> ---
>  drivers/video/backlight/qcom-wled.c | 118 +++++++++++++++++++++++++++++++++++-
>  1 file changed, 116 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/qcom-wled.c
> index 2cfba77..80ae084 100644
> --- a/drivers/video/backlight/qcom-wled.c
> +++ b/drivers/video/backlight/qcom-wled.c
> @@ -23,14 +23,20 @@
>  
>  /* From DT binding */
>  #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_MOD_EN				0x46
>  #define  WLED3_CTRL_REG_MOD_EN_MASK			BIT(7)
> +#define  WLED3_CTRL_REG_MOD_EN_BIT			BIT(7)
>  
>  #define WLED3_CTRL_REG_FREQ				0x4c
>  #define  WLED3_CTRL_REG_FREQ_MASK			GENMASK(3, 0)
> @@ -161,9 +167,12 @@ struct wled {
>  	u32 short_count;
>  	const int *version;
>  	int short_irq;
> +	int ovp_irq;
>  	bool force_mod_disable;
> +	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 +218,32 @@ 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_BIT) {
> +		if (wled->ovp_irq > 0 && wled->ovp_irq_disabled) {
> +			enable_irq(wled->ovp_irq);
> +			wled->ovp_irq_disabled = false;
> +		}
> +	} else {
> +		if (wled->ovp_irq > 0 && !wled->ovp_irq_disabled) {
> +			disable_irq(wled->ovp_irq);
> +			wled->ovp_irq_disabled = true;
> +		}
> +	}
> +}
> +
>  static int wled_module_enable(struct wled *wled, int val)
>  {
>  	int rc;
> @@ -220,7 +255,12 @@ 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;
> +
> +	schedule_delayed_work(&wled->ovp_work, WLED_SOFT_START_DLY_US);
> +
> +	return 0;
>  }
>  
>  static int wled3_sync_toggle(struct wled *wled)
> @@ -346,6 +386,36 @@ static irqreturn_t wled_short_irq_handler(int irq, void *_wled)
>  	return IRQ_HANDLED;
>  }
>  
> +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))
> +		dev_dbg(wled->dev, "WLED OVP fault detected, int_sts=%x fault_sts= %x\n",
> +			int_sts, fault_sts);
> +
> +	return IRQ_HANDLED;
> +}
> +
>  static int wled3_setup(struct wled *wled)
>  {
>  	u16 addr;
> @@ -821,6 +891,44 @@ 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;
> +	u32 val;
> +
> +	if (*wled->version == WLED_PM8941)
> +		return 0;
> +
> +	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);
> +		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)) {
> +		disable_irq(wled->ovp_irq);
> +		wled->ovp_irq_disabled = true;
> +	}
> +
> +	return rc;
> +}
> +
>  static const struct backlight_ops wled_ops = {
>  	.update_status = wled_update_status,
>  };
> @@ -874,10 +982,16 @@ static int wled_probe(struct platform_device *pdev)
>  		}
>  	}
>  
> +	INIT_DELAYED_WORK(&wled->ovp_work, wled_ovp_work);
> +
>  	rc = wled_configure_short_irq(wled, pdev);
>  	if (rc < 0)
>  		return rc;
>  
> +	rc = wled_configure_ovp_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
>