linux-kernel - Re: [PATCH v7 1/4] pwm: Imagination Technologies PWM DAC driver

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Message-ID: <54AEA727.40100@mentor.com>
Date:	Thu, 8 Jan 2015 17:49:59 +0200
From:	Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>
To:	Ezequiel Garcia <ezequiel.garcia@...tec.com>,
	Andrew Bresticker <abrestic@...omium.org>,
	Thierry Reding <thierry.reding@...il.com>,
	James Hartley <james.hartley@...tec.com>,
	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:	<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-pwm@...r.kernel.org>,
	Naidu Tellapati <Naidu.Tellapati@...tec.com>,
	Sai Masarapu <Sai.Masarapu@...tec.com>
Subject: Re: [PATCH v7 1/4] pwm: Imagination Technologies PWM DAC driver

Hi Ezequiel,

On 07.01.2015 19:20, Ezequiel Garcia wrote:
> From: Naidu Tellapati <Naidu.Tellapati@...tec.com>
> 
> The Pistachio SOC from Imagination Technologies includes a Pulse Width
> Modulation DAC which produces 1 to 4 digital bit-outputs which represent
> digital waveforms. These PWM outputs are primarily in charge of controlling
> backlight LED devices.
> 
> Reviewed-by: Andrew Bresticker <abrestic@...omium.org>
> Signed-off-by: Naidu Tellapati <Naidu.Tellapati@...tec.com>
> Signed-off-by: Sai Masarapu <Sai.Masarapu@...tec.com>
> Signed-off-by: Ezequiel Garcia <ezequiel.garcia@...tec.com>
> ---
>  drivers/pwm/Kconfig   |  13 +++
>  drivers/pwm/Makefile  |   1 +
>  drivers/pwm/pwm-img.c | 250 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 264 insertions(+)
>  create mode 100644 drivers/pwm/pwm-img.c
> 

[snip]

> +static int img_pwm_probe(struct platform_device *pdev)
> +{
> +	int ret;
> +	struct resource *res;
> +	struct img_pwm_chip *pwm;
> +
> +	pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);
> +	if (!pwm)
> +		return -ENOMEM;
> +
> +	pwm->dev = &pdev->dev;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	pwm->base = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(pwm->base))
> +		return PTR_ERR(pwm->base);
> +
> +	pwm->periph_regs = syscon_regmap_lookup_by_phandle(pdev->dev.of_node,
> +							   "img,cr-periph");
> +	if (IS_ERR(pwm->periph_regs))
> +		return PTR_ERR(pwm->periph_regs);
> +
> +	pwm->sys_clk = devm_clk_get(&pdev->dev, "sys");
> +	if (IS_ERR(pwm->sys_clk)) {
> +		dev_err(&pdev->dev, "failed to get system clock\n");
> +		return PTR_ERR(pwm->sys_clk);
> +	}
> +
> +	pwm->pwm_clk = devm_clk_get(&pdev->dev, "pwm");
> +	if (IS_ERR(pwm->pwm_clk)) {
> +		dev_err(&pdev->dev, "failed to get pwm clock\n");
> +		return PTR_ERR(pwm->pwm_clk);
> +	}
> +
> +	ret = clk_prepare_enable(pwm->sys_clk);
> +	if (ret < 0) {
> +		dev_err(&pdev->dev, "could not prepare or enable sys clock\n");
> +		return ret;
> +	}
> +
> +	ret = clk_prepare_enable(pwm->pwm_clk);
> +	if (ret < 0) {
> +		dev_err(&pdev->dev, "could not prepare or enable pwm clock\n");
> +		goto disable_sysclk;
> +	}
> +
> +	pwm->chip.dev = &pdev->dev;
> +	pwm->chip.ops = &img_pwm_ops;
> +	pwm->chip.base = -1;
> +	pwm->chip.npwm = 4;
> +
> +	ret = pwmchip_add(&pwm->chip);
> +	if (ret < 0) {
> +		dev_err(&pdev->dev, "pwmchip_add failed: %d\n", ret);
> +		goto disable_pwmclk;
> +	}
> +
> +	platform_set_drvdata(pdev, pwm);
> +
> +disable_pwmclk:
> +	clk_disable_unprepare(pwm->pwm_clk);
> +disable_sysclk:
> +	clk_disable_unprepare(pwm->sys_clk);
> +
> +	return 0;

return ret on error paths?

Also should you reenable sys and pwm clocks after successful driver
registration?

> +}
> +

--
With best wishes,
Vladimir
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