linux-kernel - Re: [PATCH v5 2/2] pwm: Add clock based PWM output driver

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Message-ID: <e1f2f9c4-a597-2c8f-df0c-4ae30a5ad594@canonical.com>
Date:   Mon, 14 Feb 2022 12:19:04 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
To:     Nikita Travkin <nikita@...n.ru>, thierry.reding@...il.com,
        lee.jones@...aro.org
Cc:     u.kleine-koenig@...gutronix.de, robh+dt@...nel.org,
        sboyd@...nel.org, linus.walleij@...aro.org, masneyb@...tation.org,
        sean.anderson@...o.com, linux-pwm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        ~postmarketos/upstreaming@...ts.sr.ht
Subject: Re: [PATCH v5 2/2] pwm: Add clock based PWM output driver

On 12/02/2022 17:23, Nikita Travkin wrote:
> Some systems have clocks exposed to external devices. If the clock
> controller supports duty-cycle configuration, such clocks can be used as
> pwm outputs. In fact PWM and CLK subsystems are interfaced with in a
> similar way and an "opposite" driver already exists (clk-pwm). Add a
> driver that would enable pwm devices to be used via clk subsystem.
> 
> Signed-off-by: Nikita Travkin <nikita@...n.ru>
> --
> 

(...)

> +
> +static int pwm_clk_probe(struct platform_device *pdev)
> +{
> +	struct pwm_clk_chip *chip;
> +	int ret;
> +
> +	chip = devm_kzalloc(&pdev->dev, sizeof(*chip), GFP_KERNEL);
> +	if (!chip)
> +		return -ENOMEM;
> +
> +	chip->clk = devm_clk_get(&pdev->dev, NULL);
> +	if (IS_ERR(chip->clk))
> +		return dev_err_probe(&pdev->dev, PTR_ERR(chip->clk),
> +				     "Failed to get clock\n");
> +
> +	chip->chip.dev = &pdev->dev;
> +	chip->chip.ops = &pwm_clk_ops;
> +	chip->chip.npwm = 1;
> +
> +	ret = clk_prepare(chip->clk);
> +	if (ret < 0)
> +		return dev_err_probe(&pdev->dev, ret, "Failed to prepare clock\n");
> +
> +	ret = pwmchip_add(&chip->chip);
> +	if (ret < 0)
> +		return dev_err_probe(&pdev->dev, ret, "Failed to add pwm chip\n");

You need to cleanup - unprepare the clock.

> +
> +	platform_set_drvdata(pdev, chip);
> +	return 0;
> +}
> +


Best regards,
Krzysztof