linux-kernel - Re: [PATCH v16] pwm: opencores: Add PWM driver support

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Message-ID: <bfwpcffdrxqjes4atio6deltu5tgmd4ing7j4yewwp6jprqmmc@rv2x3qudlzo3>
Date: Thu, 19 Dec 2024 21:59:56 +0100
From: Uwe Kleine-König <ukleinek@...nel.org>
To: William Qiu <william.qiu@...rfivetech.com>
Cc: linux-kernel@...r.kernel.org, linux-pwm@...r.kernel.org, 
	Hal Feng <hal.feng@...rfivetech.com>, Philipp Zabel <p.zabel@...gutronix.de>
Subject: Re: [PATCH v16] pwm: opencores: Add PWM driver support

Hello,

On Mon, Oct 28, 2024 at 09:46:09AM +0800, William Qiu wrote:
> +static int ocores_pwm_apply(struct pwm_chip *chip,
> +			    struct pwm_device *pwm,
> +			    const struct pwm_state *state)
> +{
> +	struct ocores_pwm_device *ddata = chip_to_ocores(chip);
> +	u32 ctrl_data = 0;
> +	u64 period_data, duty_data;
> +
> +	if (state->polarity != PWM_POLARITY_INVERSED)
> +		return -EINVAL;
> +
> +	period_data = mul_u64_u32_div(state->period, ddata->clk_rate, NSEC_PER_SEC);
> +	if (!period_data)
> +		return -EINVAL;
> +
> +	if (period_data > U32_MAX)
> +		period_data = U32_MAX;
> +
> +	ocores_pwm_writel(ddata, pwm->hwpwm, REG_OCPWM_LRC, period_data);
> +
> +	duty_data = mul_u64_u32_div(state->duty_cycle, ddata->clk_rate, NSEC_PER_SEC);
> +	if (!duty_data)
> +		return -EINVAL;

I can understand that period_data == 0 is an error, but duty_data == 0
could/should just work?!

> +
> +	if (duty_data > U32_MAX)
> +		duty_data = U32_MAX;
> +
> +	ocores_pwm_writel(ddata, pwm->hwpwm, REG_OCPWM_HRC, duty_data);
> +
> +	ctrl_data = ocores_pwm_readl(ddata, pwm->hwpwm, REG_OCPWM_CTRL);
> +	if (state->enabled)
> +		ocores_pwm_writel(ddata, pwm->hwpwm, REG_OCPWM_CTRL,
> +				  ctrl_data | REG_OCPWM_CNTR_EN | REG_OCPWM_CNTR_OE);
> +	else
> +		ocores_pwm_writel(ddata, pwm->hwpwm, REG_OCPWM_CTRL,
> +				  ctrl_data & ~(REG_OCPWM_CNTR_EN | REG_OCPWM_CNTR_OE));
> +
> +	return 0;
> +}
> [...]
> +static int ocores_pwm_probe(struct platform_device *pdev)
> +{
> +	const struct of_device_id *id;
> +	struct device *dev = &pdev->dev;
> +	struct ocores_pwm_device *ddata;
> +	struct pwm_chip *chip;
> +	struct clk *clk;
> +	struct reset_control *rst;
> +	int ret;
> +
> +	id = of_device_get_match_data(&pdev->dev);
> +	if (!id)
> +		return -ENODEV;
> +
> +	chip = devm_pwmchip_alloc(&pdev->dev, 8, sizeof(*ddata));
> +	if (IS_ERR(chip))
> +		return -ENOMEM;
> +
> +	ddata = chip_to_ocores(chip);
> +	ddata->data = id->data;
> +	chip->ops = &ocores_pwm_ops;
> +
> +	ddata->regs = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(ddata->regs))
> +		return dev_err_probe(dev, PTR_ERR(ddata->regs),
> +				     "Unable to map IO resources\n");
> +
> +	clk = devm_clk_get_enabled(dev, NULL);
> +	if (IS_ERR(clk))
> +		return dev_err_probe(dev, PTR_ERR(clk),
> +				     "Unable to get pwm's clock\n");
> +
> +	ret = devm_clk_rate_exclusive_get(dev, clk);
> +	if (ret)
> +		return ret;
> +
> +	rst = devm_reset_control_get_optional_exclusive(dev, NULL);
> +	if (IS_ERR(rst))
> +		return dev_err_probe(dev, PTR_ERR(rst),
> +				     "Unable to get pwm's reset\n");
> +
> +	ret = reset_control_deassert(rst);
> +	if (ret)
> +		return ret;
> +
> +	ret = devm_add_action_or_reset(dev, ocores_pwm_reset_control_assert, rst);
> +	if (ret)
> +		return ret;
> +
> +	ddata->clk_rate = clk_get_rate(clk);
> +	if (ddata->clk_rate > NSEC_PER_SEC)
> +		return -EINVAL;

Missing error messages for the three checks above.

> +	ret = devm_pwmchip_add(dev, chip);
> +	if (ret < 0)
> +		return dev_err_probe(dev, ret, "Could not register PWM chip\n");
> +
> +	return 0;
> +}

Best regards
Uwe

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