Re: [RFC PATCH] pwm: atmel-pwm: add pwm controller driver

[Nicolas Ferre <nicolas.ferre@atmel.com>]

On 19/08/2013 05:11, Bo Shen :
> add atmel pwm controller driver based on PWM framework
>
> this is basic function implementation of pwm controller
> it can work with pwm based led and backlight
>
> Signed-off-by: Bo Shen <voice.shen@atmel.com>
>
> ---
> This patch is based on Linux v3.11 rc6
> Tested on sama5d31ek and at91sam9m10g45ek board
> ---
>   .../devicetree/bindings/pwm/atmel-pwm.txt          |   19 ++
>   drivers/pwm/Kconfig                                |    9 +
>   drivers/pwm/Makefile                               |    1 +
>   drivers/pwm/pwm-atmel.c                            |  327 ++++++++++++++++++++
>   4 files changed, 356 insertions(+)
>   create mode 100644 Documentation/devicetree/bindings/pwm/atmel-pwm.txt
>   create mode 100644 drivers/pwm/pwm-atmel.c
>
> diff --git a/Documentation/devicetree/bindings/pwm/atmel-pwm.txt b/Documentation/devicetree/bindings/pwm/atmel-pwm.txt
> new file mode 100644
> index 0000000..127fcdb
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/pwm/atmel-pwm.txt
> @@ -0,0 +1,19 @@
> +Atmel PWM controller
> +
> +Required properties:
> +  - compatible: should be one of:
> +    - "atmel,at91sam9rl-pwm"
> +    - "atmel,sama5-pwm"

No, the compatibility string should be: "atmel,sama5d3-pwm"

> +  - reg: physical base address and length of the controller's registers
> +  - #pwm-cells: Should be 3.
> +    - The first cell specifies the per-chip index of the PWM to use
> +    - The second cell is the period in nanoseconds
> +    - The third cell is used to encode the polarity of PWM output
> +
> +Example:
> +
> +	pwm0: pwm@f8034000 {
> +		compatible = "atmel,at91sam9rl-pwm";
> +		reg = <0xf8034000 0x400>;
> +		#pwm-cells = <3>;
> +	};

Can you add an example of consumer: it would make the example much more 
understandable.

> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> index 75840b5..54237b9 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -41,6 +41,15 @@ config PWM_AB8500
>   	  To compile this driver as a module, choose M here: the module
>   	  will be called pwm-ab8500.
>
> +config PWM_ATMEL
> +	tristate "Atmel PWM support"
> +	depends on ARCH_AT91
> +	help
> +	  Generic PWM framework driver for Atmel SoC.
> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called pwm-atmel.
> +
>   config PWM_ATMEL_TCB
>   	tristate "Atmel TC Block PWM support"
>   	depends on ATMEL_TCLIB && OF
> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
> index 77a8c18..5b193f8 100644
> --- a/drivers/pwm/Makefile
> +++ b/drivers/pwm/Makefile
> @@ -1,6 +1,7 @@
>   obj-$(CONFIG_PWM)		+= core.o
>   obj-$(CONFIG_PWM_SYSFS)		+= sysfs.o
>   obj-$(CONFIG_PWM_AB8500)	+= pwm-ab8500.o
> +obj-$(CONFIG_PWM_ATMEL)		+= pwm-atmel.o
>   obj-$(CONFIG_PWM_ATMEL_TCB)	+= pwm-atmel-tcb.o
>   obj-$(CONFIG_PWM_BFIN)		+= pwm-bfin.o
>   obj-$(CONFIG_PWM_IMX)		+= pwm-imx.o
> diff --git a/drivers/pwm/pwm-atmel.c b/drivers/pwm/pwm-atmel.c
> new file mode 100644
> index 0000000..b83d68e
> --- /dev/null
> +++ b/drivers/pwm/pwm-atmel.c
> @@ -0,0 +1,327 @@
> +/*
> + * Driver for Atmel Pulse Width Modulation Controller
> + *
> + * Copyright (C) 2013 Atmel Semiconductor Technology Ltd.

use "Atmel Corporation" in copyright.

> + *		 Bo Shen <voice.shen@atmel.com>
> + *
> + * GPL v2 or later
> + */

A general remark also pointed out by Thierry: please use more defined 
constants in your code: it makes the code more readable and avoid this 
black magic feeling when we read it.


> +#include <linux/clk.h>
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/pinctrl/consumer.h>
> +#include <linux/platform_device.h>
> +#include <linux/pwm.h>
> +#include <linux/slab.h>
> +
> +#define PWM_MR		0x00
> +#define PWM_ENA		0x04
> +#define PWM_DIS		0x08
> +#define PWM_SR		0x0C
> +
> +#define PWM_CMR		0x00
> +
> +/* The following register for PWM v1 */
> +#define PWMv1_CDTY	0x04
> +#define PWMv1_CPRD	0x08
> +#define PWMv1_CUPD	0x10
> +
> +/* The following register for PWM v2 */
> +#define PWMv2_CDTY	0x04
> +#define PWMv2_CDTYUPD	0x08
> +#define PWMv2_CPRD	0x0C
> +#define PWMv2_CPRDUPD	0x10
> +
> +#define PWM_NUM		4
> +
> +struct atmel_pwm_chip {
> +	struct pwm_chip chip;
> +	struct clk *clk;
> +	void __iomem *base;
> +
> +	void (*config)(struct atmel_pwm_chip *chip, struct pwm_device *pwm,
> +			unsigned int dty, unsigned int prd);
> +};
> +
> +#define to_atmel_pwm_chip(chip) container_of(chip, struct atmel_pwm_chip, chip)
> +
> +static inline u32 atmel_pwm_readl(struct atmel_pwm_chip *chip, int offset)
> +{
> +	return readl(chip->base + offset);
> +}
> +
> +static inline void atmel_pwm_writel(struct atmel_pwm_chip *chip, int offset,
> +		u32 val)
> +{
> +	writel(val, chip->base + offset);
> +}
> +
> +static inline u32 atmel_pwm_ch_readl(struct atmel_pwm_chip *chip, int ch,
> +		int offset)
> +{
> +	return readl(chip->base + 0x200 + ch * 0x20 + offset);

Maybe a constant for this 0x200 value...

> +}
> +
> +static inline void atmel_pwm_ch_writel(struct atmel_pwm_chip *chip, int ch,
> +		int offset, u32 val)
> +{
> +	writel(val, chip->base + 0x200 + ch * 0x20 + offset);
> +}
> +
> +static int atmel_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
> +		int duty_ns, int period_ns)
> +{
> +	struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
> +	unsigned long long val, prd, dty;
> +	unsigned long long div, clk_rate;
> +	int ret, pres = 0;
> +
> +	clk_rate = clk_get_rate(atmel_pwm->clk);
> +
> +	while (1) {

Why not use a proper loop condition here instead of a frightening
while (true) loop? Is it really making the code less readable?

> +		div = 1000000000;

use a constant or at least a comment for this initialization.

> +		div *= 1 << pres;
> +		val = clk_rate * period_ns;
> +		prd = div_u64(val, div);
> +		val = clk_rate * duty_ns;
> +		dty = div_u64(val, div);
> +
> +		if (prd < 0x0001 || dty < 0x0)
> +			return -EINVAL;
> +
> +		if (prd > 0xffff || dty > 0xffff) {

Yes, here define those constants please.

> +			if (++pres > 0x10)
> +				return -EINVAL;
> +			continue;
> +		}
> +
> +		break;
> +	}
> +
> +	/* Enable clock */
> +	ret = clk_prepare_enable(atmel_pwm->clk);
> +	if (ret) {
> +		pr_err("failed to enable pwm clock\n");
> +		return ret;
> +	}
> +
> +	atmel_pwm->config(atmel_pwm, pwm, dty, prd);
> +
> +	/* Check whether need to disable clock */
> +	val = atmel_pwm_readl(atmel_pwm, PWM_SR);
> +	if ((val & 0xf) == 0)

Ditto.

> +		clk_disable_unprepare(atmel_pwm->clk);
> +
> +	return 0;
> +}
> +
> +static void atmel_pwm_config_v1(struct atmel_pwm_chip *atmel_pwm,
> +		struct pwm_device *pwm, unsigned int dty, unsigned int prd)
> +{
> +	unsigned int val;
> +
> +	/*
> +	 * if the pwm channel is enabled, using update register to update
> +	 * related register value, or else write it directly
> +	 */
> +	if (test_bit(PWMF_ENABLED, &pwm->flags)) {
> +		atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWMv1_CUPD, dty);
> +
> +		val = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm, PWM_CMR);
> +		val &= ~(1 << 10);
> +		atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWM_CMR, val);
> +	} else {
> +		atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWMv1_CDTY, dty);
> +		atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWMv1_CPRD, prd);
> +	}
> +}
> +
> +static void atmel_pwm_config_v2(struct atmel_pwm_chip *atmel_pwm,
> +		struct pwm_device *pwm, unsigned int dty, unsigned int prd)
> +{
> +	/*
> +	 * if the pwm channel is enabled, using update register to update
> +	 * related register value, or else write it directly
> +	 */
> +	if (test_bit(PWMF_ENABLED, &pwm->flags)) {
> +		atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWMv2_CDTYUPD, dty);
> +		atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWMv2_CPRDUPD, prd);
> +	} else {
> +		atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWMv2_CDTY, dty);
> +		atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWMv2_CPRD, prd);
> +	}
> +}
> +
> +static int atmel_pwm_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
> +		enum pwm_polarity polarity)
> +{
> +	struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
> +	u32 val = 0;
> +	int ret;
> +
> +	/* Enable clock */
> +	ret = clk_prepare_enable(atmel_pwm->clk);
> +	if (ret) {
> +		pr_err("failed to enable pwm clock\n");
> +		return ret;
> +	}
> +
> +	if (polarity == PWM_POLARITY_NORMAL)
> +		val &= ~(1 << 9);
> +	else
> +		val |= 1 << 9;

Ditto.

> +
> +	atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWM_CMR, val);
> +
> +	/* Disable clock */
> +	clk_disable_unprepare(atmel_pwm->clk);
> +
> +	return 0;
> +}
> +
> +static int atmel_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
> +{
> +	struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
> +
> +	clk_prepare_enable(atmel_pwm->clk);
> +
> +	atmel_pwm_writel(atmel_pwm, PWM_ENA, 1 << pwm->hwpwm);
> +
> +	return 0;
> +}
> +
> +static void atmel_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
> +{
> +	struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
> +	u32 val;
> +
> +	atmel_pwm_writel(atmel_pwm, PWM_DIS, 1 << pwm->hwpwm);
> +
> +	/* Disable clock */
> +	val = atmel_pwm_readl(atmel_pwm, PWM_SR);
> +	if ((val & 0xf) == 0)
> +		clk_disable_unprepare(atmel_pwm->clk);
> +}
> +
> +static const struct pwm_ops atmel_pwm_ops = {
> +	.config = atmel_pwm_config,
> +	.set_polarity = atmel_pwm_set_polarity,
> +	.enable = atmel_pwm_enable,
> +	.disable = atmel_pwm_disable,
> +	.owner = THIS_MODULE,
> +};
> +
> +struct atmel_pwm_data {
> +	void (*config)(struct atmel_pwm_chip *chip, struct pwm_device *pwm,
> +			unsigned int dty, unsigned int prd);
> +};
> +
> +static struct atmel_pwm_data atmel_pwm_data_v1 = {
> +	.config = atmel_pwm_config_v1,
> +};
> +
> +static struct atmel_pwm_data atmel_pwm_data_v2 = {
> +	.config = atmel_pwm_config_v2,
> +};
> +
> +static const struct of_device_id atmel_pwm_dt_ids[] = {
> +	{
> +		.compatible = "atmel,at91sam9rl-pwm",
> +		.data = &atmel_pwm_data_v1,
> +	}, {
> +		.compatible = "atmel,sama5-pwm",
> +		.data = &atmel_pwm_data_v2,
> +	}, {
> +		/* sentinel */
> +	},
> +};
> +MODULE_DEVICE_TABLE(of, atmel_pwm_dt_ids);
> +
> +static int atmel_pwm_probe(struct platform_device *pdev)
> +{
> +	const struct of_device_id *of_id =
> +		of_match_device(atmel_pwm_dt_ids, &pdev->dev);
> +	const struct atmel_pwm_data *data;
> +	struct atmel_pwm_chip *atmel_pwm;
> +	struct resource *res;
> +	struct pinctrl *pinctrl;
> +	int ret;
> +
> +	pinctrl = devm_pinctrl_get_select_default(&pdev->dev);
> +	if (IS_ERR(pinctrl)) {
> +		dev_err(&pdev->dev, "failed get pinctrl\n");
> +		return PTR_ERR(pinctrl);
> +	}

As said by Thierry: already done in core driver code.

> +
> +	atmel_pwm = devm_kzalloc(&pdev->dev, sizeof(*atmel_pwm), GFP_KERNEL);
> +	if (!atmel_pwm) {
> +		dev_err(&pdev->dev, "out of memory\n");
> +		return -ENOMEM;
> +	}
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (!res) {
> +		dev_err(&pdev->dev, "no memory resource defined\n");
> +		return -ENODEV;
> +	}
> +
> +	atmel_pwm->base = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(atmel_pwm->base)) {
> +		dev_err(&pdev->dev, "ioremap failed\n");
> +		return PTR_ERR(atmel_pwm->base);
> +	}
> +
> +	atmel_pwm->clk = devm_clk_get(&pdev->dev, "pwm_clk");
> +	if (IS_ERR(atmel_pwm->clk)) {
> +		dev_err(&pdev->dev, "clk get failed\n");
> +		return PTR_ERR(atmel_pwm->clk);
> +	}
> +
> +	atmel_pwm->chip.dev = &pdev->dev;
> +	atmel_pwm->chip.ops = &atmel_pwm_ops;
> +	atmel_pwm->chip.of_xlate = of_pwm_xlate_with_flags;
> +	atmel_pwm->chip.of_pwm_n_cells = 3;
> +	atmel_pwm->chip.base = -1;
> +	atmel_pwm->chip.npwm = PWM_NUM;
> +
> +	data = of_id->data;
> +	atmel_pwm->config = data->config;
> +
> +	ret = pwmchip_add(&atmel_pwm->chip);
> +	if (ret < 0) {
> +		dev_err(&pdev->dev, "failed to add pwm chip %d\n", ret);
> +		return ret;
> +	}
> +
> +	platform_set_drvdata(pdev, atmel_pwm);
> +
> +	dev_info(&pdev->dev, "successfully register pwm\n");
> +
> +	return 0;
> +}
> +
> +static int atmel_pwm_remove(struct platform_device *pdev)
> +{
> +	struct atmel_pwm_chip *atmel_pwm = platform_get_drvdata(pdev);
> +
> +	return pwmchip_remove(&atmel_pwm->chip);
> +}
> +
> +static struct platform_driver atmel_pwm_driver = {
> +	.driver = {
> +		.name = "atmel-pwm",
> +		.of_match_table = of_match_ptr(atmel_pwm_dt_ids),
> +	},
> +	.probe = atmel_pwm_probe,
> +	.remove = atmel_pwm_remove,
> +};
> +module_platform_driver(atmel_pwm_driver);
> +
> +MODULE_ALIAS("platform:atmel-pwm");
> +MODULE_AUTHOR("Bo Shen <voice.shen@atmel.com>");
> +MODULE_DESCRIPTION("Atmel PWM driver");
> +MODULE_LICENSE("GPL v2");
>


-- 
Nicolas Ferre