linux-kernel - Re: [PATCH v2 15/15] video: backlight: mt6370: Add Mediatek MT6370 support

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Message-ID: <20220613170853.bffuwkcmflfgg4gt@ash.lan>
Date:   Mon, 13 Jun 2022 18:08:53 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     ChiaEn Wu <peterwu.pub@...il.com>
Cc:     jic23@...nel.org, lars@...afoo.de, matthias.bgg@...il.com,
        lee.jones@...aro.org, jingoohan1@...il.com, pavel@....cz,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        linux-iio@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linux-leds@...r.kernel.org,
        devicetree@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-usb@...r.kernel.org, linux-fbdev@...r.kernel.org,
        szunichen@...il.com, ChiaEn Wu <chiaen_wu@...htek.com>
Subject: Re: [PATCH v2 15/15] video: backlight: mt6370: Add Mediatek MT6370
 support

On Mon, Jun 13, 2022 at 07:11:46PM +0800, ChiaEn Wu wrote:
> +static int mt6370_init_backlight_properties(struct mt6370_priv *priv,
> +					    struct backlight_properties *props)

Most of the changes in this version looks good... but it looks the new
code in this function has a number of problems. See below...


> +{
> +	struct device *dev = priv->dev;
> +	u8 prop_val;
> +	u32 brightness;
> +	unsigned int mask, val;
> +	int ret;
> +
> +	/* Vendor optional properties
> +	 * if property not exist, keep value in default.
> +	 */

That's not the right strategy for booleans. Not existing means false
(e.g. flags should actively be unset).


> +	if (device_property_read_bool(dev, "mediatek,bled-pwm-enable")) {
> +		ret = regmap_update_bits(priv->regmap, MT6370_REG_BL_PWM,
> +					 MT6370_BL_PWM_EN_MASK,
> +					 MT6370_BL_PWM_EN_MASK);
> +		if (ret)
> +			return ret;
> +	}

As above comment... all of the boolean properties are now being read
incorrectly.


> +
> +	if (device_property_read_bool(dev, "mediatek,bled-pwm-hys-enable")) {
> +		ret = regmap_update_bits(priv->regmap, MT6370_REG_BL_PWM,
> +					 MT6370_BL_PWM_HYS_EN_MASK,
> +					 MT6370_BL_PWM_HYS_EN_MASK);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	ret = device_property_read_u8(dev, "mediatek,bled-pwm-hys-input-bit",
> +				      &prop_val);
> +	if (!ret) {
> +		val = min_t(u8, prop_val, 3)
> +		      << (ffs(MT6370_BL_PWM_HYS_SEL_MASK) - 1);
> +		ret = regmap_update_bits(priv->regmap, MT6370_REG_BL_PWM,
> +					 MT6370_BL_PWM_HYS_SEL_MASK, val);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	ret = device_property_read_u8(dev, "mediatek,bled-ovp-microvolt",
> +				      &prop_val);
> +	if (!ret) {
> +		val = min_t(u8, prop_val, 3)
> +		      << (ffs(MT6370_BL_OVP_SEL_MASK) - 1);

This has been renamed but still seems to the using 0, 1, 2, 3 rather
than an actual value in microvolts.


> +		ret = regmap_update_bits(priv->regmap, MT6370_REG_BL_BSTCTRL,
> +					 MT6370_BL_OVP_SEL_MASK, val);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	if (device_property_read_bool(dev, "mediatek,bled-ovp-shutdown")) {
> +		ret = regmap_update_bits(priv->regmap, MT6370_REG_BL_BSTCTRL,
> +					 MT6370_BL_OVP_EN_MASK,
> +					 MT6370_BL_OVP_EN_MASK);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	ret = device_property_read_u8(dev, "mediatek,bled-ocp-microamp",
> +				      &prop_val);
> +	if (!ret) {
> +		val = min_t(u8, prop_val, 3)
> +		      << (ffs(MT6370_BL_OC_SEL_MASK) - 1);

Likewise, should this be accepting a value in microamps?


> +		ret = regmap_update_bits(priv->regmap, MT6370_REG_BL_BSTCTRL,
> +					 MT6370_BL_OC_SEL_MASK, val);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	if (device_property_read_bool(dev, "mediatek,bled-ocp-shutdown")) {
> +		ret = regmap_update_bits(priv->regmap, MT6370_REG_BL_BSTCTRL,
> +					 MT6370_BL_OC_EN_MASK,
> +					 MT6370_BL_OC_EN_MASK);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	/* Common properties */
> +	ret = device_property_read_u32(dev, "max-brightness", &brightness);
> +	if (ret)
> +		brightness = MT6370_BL_MAX_BRIGHTNESS;
> +
> +	props->max_brightness = min_t(u32, brightness,
> +				      MT6370_BL_MAX_BRIGHTNESS);
> +
> +	ret = device_property_read_u32(dev, "default-brightness", &brightness);
> +	if (ret)
> +		brightness = props->max_brightness;
> +
> +	props->brightness = min_t(u32, brightness, props->max_brightness);
> +
> +
> +	ret = device_property_read_u8(dev, "mediatek,bled-channel-use",
> +				      &prop_val);
> +	if (ret) {
> +		dev_err(dev, "mediatek,bled-channel-use DT property missing\n");
> +		return ret;
> +	}
> +
> +	if (!prop_val || prop_val > MT6370_BL_MAX_CH) {
> +		dev_err(dev, "No channel specified (ch_val:%d)\n", prop_val);

Error string has not been updated to match condition that triggers it.


> +		return -EINVAL;
> +	}


Daniel.