linux-kernel - Re: [PATCH 02/10] pwm: Add SI-EN SN3112 PWM support

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Date: Wed, 24 Apr 2024 21:37:25 +0200
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: wuxilin123@...il.com, Uwe Kleine-König
 <u.kleine-koenig@...gutronix.de>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Junhao Xie <bigfoot@...ssfun.cn>,
 Neil Armstrong <neil.armstrong@...aro.org>,
 Jessica Zhang <quic_jesszhan@...cinc.com>, Sam Ravnborg <sam@...nborg.org>,
 David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 Bjorn Andersson <andersson@...nel.org>,
 Tengfei Fan <quic_tengfan@...cinc.com>,
 Molly Sophia <mollysophia379@...il.com>
Cc: linux-pwm@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 02/10] pwm: Add SI-EN SN3112 PWM support



On 4/24/24 17:29, Xilin Wu via B4 Relay wrote:
> From: Junhao Xie <bigfoot@...ssfun.cn>
> 
> Add a new driver for the SI-EN SN3112 12-channel 8-bit PWM LED controller.
> 
> Signed-off-by: Junhao Xie <bigfoot@...ssfun.cn>
> ---

[...]

> +static int sn3112_set_en_reg(struct sn3112 *priv, unsigned int channel,
> +			     bool enabled, bool write)
> +{
> +	unsigned int reg, bit;
> +
> +	if (channel >= SN3112_CHANNELS)
> +		return -EINVAL;
> +
> +	/* LED_EN1: BIT5:BIT3 = OUT3:OUT1 */
> +	if (channel >= 0 && channel <= 2)
> +		reg = 0, bit = channel + 3;
> +	/* LED_EN2: BIT5:BIT0 = OUT9:OUT4 */
> +	else if (channel >= 3 && channel <= 8)
> +		reg = 1, bit = channel - 3;
> +	/* LED_EN3: BIT2:BIT0 = OUT12:OUT10 */
> +	else if (channel >= 9 && channel <= 11)
> +		reg = 2, bit = channel - 9;
> +	else
> +		return -EINVAL;
> +
> +	dev_dbg(priv->pdev, "channel %u enabled %u\n", channel, enabled);
> +	dev_dbg(priv->pdev, "reg %u bit %u\n", reg, bit);
> +	if (enabled)
> +		set_bit(bit, (ulong *)&priv->pwm_en_reg[reg]);
> +	else
> +		clear_bit(bit, (ulong *)&priv->pwm_en_reg[reg]);
> +	dev_dbg(priv->pdev, "set enable reg %u to %u\n", reg,
> +		priv->pwm_en_reg[reg]);
> +
> +	if (!write)
> +		return 0;
> +	return sn3112_write_reg(priv, SN3112_REG_PWM_EN + reg,
> +				priv->pwm_en_reg[reg]);

This looks like a weird reimplementation of regmap_update_bits


> +}
> +
> +static int sn3112_set_val_reg(struct sn3112 *priv, unsigned int channel,
> +			      uint8_t val, bool write)
> +{
> +	if (channel >= SN3112_CHANNELS)
> +		return -EINVAL;
> +	priv->pwm_val[channel] = val;
> +	dev_dbg(priv->pdev, "set value reg %u to %u\n", channel,
> +		priv->pwm_val[channel]);
> +
> +	if (!write)
> +		return 0;

There's only a single call, with write == true

> +	return sn3112_write_reg(priv, SN3112_REG_PWM_VAL + channel,
> +				priv->pwm_val[channel]);
> +}
> +
> +static int sn3112_write_all(struct sn3112 *priv)
> +{
> +	int i, ret;
> +
> +	/* regenerate enable register values */
> +	for (i = 0; i < SN3112_CHANNELS; i++) {
> +		ret = sn3112_set_en_reg(priv, i, priv->pwm_en[i], false);
> +		if (ret != 0)
> +			return ret;
> +	}
> +
> +	/* use random value to clear all registers */
> +	ret = sn3112_write_reg(priv, SN3112_REG_RESET, 0x66);
> +	if (ret != 0)

if (ret) is the same as if (ret != 0)

[...]

> +
> +	/* use random value to apply changes */
> +	ret = sn3112_write_reg(priv, SN3112_REG_APPLY, 0x66);

"a random value"? sounds suspicious..

> +	if (ret != 0)
> +		return ret;
> +
> +	dev_dbg(priv->pdev, "reinitialized\n");

Please remove such "got here" messages once you're done with testing
the driver locally

[...]

> +
> +#if IS_ENABLED(CONFIG_GPIOLIB)

I'm not sure this would be ever disabled on any embedded system nowadays.
Especially with I2C.

[...]

> +
> +	dev_info(&client->dev,
> +		 "Found SI-EN SN3112 12-channel 8-bit PWM LED controller\n");

This sort of message only makes sense if there's a CHIP_ID register that
you can actually validate. If you bind this driver to a device at the same
expected address, it will say it's there even if it's not.


> +	return 0;
> +}
> +
> +static void sn3112_pwm_remove(struct i2c_client *client)
> +{
> +	struct pwm_chip *chip = i2c_get_clientdata(client);
> +	struct sn3112 *priv = pwmchip_get_drvdata(chip);
> +
> +	dev_dbg(priv->pdev, "remove\n");
> +
> +	/* set software enable register */
> +	sn3112_write_reg(priv, SN3112_REG_ENABLE, 0);
> +
> +	/* use random value to apply changes */
> +	sn3112_write_reg(priv, SN3112_REG_APPLY, 0x66);
> +
> +#if IS_ENABLED(CONFIG_GPIOLIB)
> +	/* enable hardware shutdown pin */
> +	if (priv->sdb)
> +		gpiod_set_value(priv->sdb, 1);
> +#endif
> +
> +	/* power-off sn5112 power vdd */
> +	regulator_disable(priv->vdd);
> +
> +	pwmchip_remove(chip);

devm_pwmchip_add?

Konrad