Re: [PATCH] pwm: add lpc32xx pwm support

[Thierry Reding <thierry.reding-RM9K5IK7kjKj5M59NBduVrNAH6kLmebB@public.gmane.org>]

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On Mon, Jul 09, 2012 at 04:27:54PM -0300, Alexandre Pereira da Silva wrote:
> Add lpc32xx soc pwm driver.
> 
> Signed-off-by: Alexandre Pereira da Silva <aletes.xgr-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> ---
>  .../devicetree/bindings/pwm/lpc32xx-pwm.txt        |   12 ++
>  drivers/pwm/Kconfig                                |   11 ++
>  drivers/pwm/Makefile                               |    1 +
>  drivers/pwm/pwm-lpc32xx.c                          |  151 ++++++++++++++++++++
>  4 files changed, 175 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/pwm/lpc32xx-pwm.txt
>  create mode 100644 drivers/pwm/pwm-lpc32xx.c

Hi Alexandre,

overall this looks good, just some comments inline. I'd very much
appreciate an Acked-by from Roland on this.

> diff --git a/Documentation/devicetree/bindings/pwm/lpc32xx-pwm.txt b/Documentation/devicetree/bindings/pwm/lpc32xx-pwm.txt
> new file mode 100644
> index 0000000..fb7b3d5
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/pwm/lpc32xx-pwm.txt
> @@ -0,0 +1,12 @@
> +LPC32XX PWM controller
> +
> +Required properties:
> +- compatible: should be "nxp,lpc3220-pwm"

Does the compatible have to be lpc3220-pwm? Can't it be lpc32xx-pwm to
match the driver and binding names?

> +- reg: physical base address and length of the controller's registers
> +
> +Example:
> +
> +pwm: pwm@80064000 {
> +	compatible = "nxp,lpc3220-pwm";
> +	reg = <0x80064000 2000>;

You probably want to specify the size as 0x2000 as well.

> +};
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> index 0b2800f..34086b1 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -28,6 +28,17 @@ config PWM_IMX
>  	  To compile this driver as a module, choose M here: the module
>  	  will be called pwm-imx.
>  
> +config PWM_LPC32XX
> +	tristate "LPC32XX PWM support"
> +	depends on ARCH_LPC32XX
> +	help
> +	  Generic PWM framework driver for LPC32XX. The LPC32XX soc has two
> +	  pwm channels.

Can we keep the spelling consistent here? It should be "PWM" and "SoC".
It'd be nice if you could fix that up in the commit message as well.

> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called pwm-lpc32xx.
> +
> +
>  config PWM_MXS
>  	tristate "Freescale MXS PWM support"
>  	depends on ARCH_MXS && OF
> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
> index cec2500..5459702 100644
> --- a/drivers/pwm/Makefile
> +++ b/drivers/pwm/Makefile
> @@ -1,6 +1,7 @@
>  obj-$(CONFIG_PWM)		+= core.o
>  obj-$(CONFIG_PWM_BFIN)		+= pwm-bfin.o
>  obj-$(CONFIG_PWM_IMX)		+= pwm-imx.o
> +obj-$(CONFIG_PWM_LPC32XX)	+= pwm-lpc32xx.o
>  obj-$(CONFIG_PWM_MXS)		+= pwm-mxs.o
>  obj-$(CONFIG_PWM_PXA)		+= pwm-pxa.o
>  obj-$(CONFIG_PWM_SAMSUNG)	+= pwm-samsung.o
> diff --git a/drivers/pwm/pwm-lpc32xx.c b/drivers/pwm/pwm-lpc32xx.c
> new file mode 100644
> index 0000000..c7fa126
> --- /dev/null
> +++ b/drivers/pwm/pwm-lpc32xx.c
> @@ -0,0 +1,151 @@
> +/*
> + * Copyright 2012 Alexandre Pereira da Silva <aletes.xgr-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> + *
> + * The code contained herein is licensed under the GNU General Public
> + * License. You may obtain a copy of the GNU General Public License
> + * Version 2 or later at the following locations:
> + *
> + * http://www.opensource.org/licenses/gpl-license.html
> + * http://www.gnu.org/copyleft/gpl.html
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/platform_device.h>
> +#include <linux/pwm.h>
> +#include <linux/slab.h>
> +
> +struct lpc32xx_pwm_chip {
> +	struct pwm_chip chip;
> +	struct device *dev;

Can you drop this field? You initialize it, but it is never used
subsequently in the driver.

> +	struct clk *clk;
> +	void __iomem *base;
> +};
> +
> +#define PWM_ENABLE (1<<31)
> +#define PWM_RELOADV(x)	(((x) & 0xFF)<<8)
> +#define PWM_DUTY(x)	((x) & 0xFF)

There should be spaces around <<.

> +
> +#define to_lpc32xx_pwm_chip(_chip) \
> +	container_of(_chip, struct lpc32xx_pwm_chip, chip)
> +
> +static int lpc32xx_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
> +			  int duty_ns, int period_ns)

The alignment looks wrong here. It seems like you aligned properly
before adding the "static".

> +{
> +	struct lpc32xx_pwm_chip *lpc32xx = to_lpc32xx_pwm_chip(chip);
> +	unsigned long long c;
> +	int period_cycles, duty_cycles;
> +
> +	c = clk_get_rate(lpc32xx->clk)/256;

Spaces around /.

> +	c = c * period_ns;
> +	do_div(c, NSEC_PER_SEC);
> +
> +	/* Handle high and low extremes */
> +	if (c == 0)
> +		c = 1;
> +	if (c > 255)
> +		c = 0; /* 0 set division by 256 */
> +	period_cycles = c;
> +
> +	c = 256*duty_ns;

Spaces around *.

> +	do_div(c, period_ns);
> +	duty_cycles = c;
> +
> +	writel(PWM_ENABLE | PWM_RELOADV(period_cycles) | PWM_DUTY(duty_cycles),
> +		lpc32xx->base);
> +
> +	return 0;
> +}
> +
> +static int lpc32xx_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
> +{
> +	struct lpc32xx_pwm_chip *lpc32xx = to_lpc32xx_pwm_chip(chip);
> +
> +	clk_enable(lpc32xx->clk);
> +	return 0;
> +}
> +
> +static void lpc32xx_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
> +{
> +	struct lpc32xx_pwm_chip *lpc32xx = to_lpc32xx_pwm_chip(chip);
> +
> +	writel(0, lpc32xx->base);
> +	clk_disable(lpc32xx->clk);
> +}
> +
> +static const struct pwm_ops lpc32xx_pwm_ops = {
> +	.config = lpc32xx_pwm_config,
> +	.enable = lpc32xx_pwm_enable,
> +	.disable = lpc32xx_pwm_disable,
> +	.owner = THIS_MODULE,
> +};
> +
> +static int lpc32xx_pwm_probe(struct platform_device *pdev)
> +{
> +	struct lpc32xx_pwm_chip *lpc32xx;
> +	struct resource *res;
> +	int ret;
> +
> +	lpc32xx = devm_kzalloc(&pdev->dev, sizeof(*lpc32xx), GFP_KERNEL);
> +	if (!lpc32xx)
> +		return -ENOMEM;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);

You should probably check for res != NULL.

> +	lpc32xx->base = devm_request_and_ioremap(&pdev->dev, res);
> +	if (!lpc32xx->base)
> +		return -EADDRNOTAVAIL;
> +
> +	lpc32xx->clk = devm_clk_get(&pdev->dev, NULL);
> +	if (IS_ERR(lpc32xx->clk))
> +		return PTR_ERR(lpc32xx->clk);
> +
> +	lpc32xx->chip.dev = &pdev->dev;
> +	lpc32xx->chip.ops = &lpc32xx_pwm_ops;
> +	lpc32xx->chip.npwm = 1;

The Kconfig help text says that the lpc32xx PWM controller has two
channels. Why is npwm set to 1 here?

> +
> +	ret = pwmchip_add(&lpc32xx->chip);
> +	if (ret < 0) {
> +		dev_err(&pdev->dev, "failed to add pwm chip %d\n", ret);

You should probably separate the error code, to make it obvious what it
is. Otherwise one might mistake this as an index. While at it, please
make PWM uppercase.

> +		return ret;
> +	}
> +
> +	lpc32xx->dev = &pdev->dev;

As I mentioned above, this is unused so it can probably be dropped.

> +	platform_set_drvdata(pdev, lpc32xx);
> +
> +	return 0;
> +}
> +
> +static int __devexit lpc32xx_pwm_remove(struct platform_device *pdev)
> +{
> +	struct lpc32xx_pwm_chip *lpc32xx = platform_get_drvdata(pdev);
> +
> +	pwmchip_remove(&lpc32xx->chip);

You should propagate potential errors from pwmchip_remove(). There are
situations where it can actually fail.

Thierry

> +
> +	return 0;
> +}
> +
> +static struct of_device_id lpc32xx_pwm_dt_ids[] = {
> +	{ .compatible = "nxp,lpc3220-pwm", },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, lpc32xx_pwm_dt_ids);
> +
> +static struct platform_driver lpc32xx_pwm_driver = {
> +	.driver = {
> +		.name = "lpc32xx-pwm",
> +		.of_match_table = of_match_ptr(lpc32xx_pwm_dt_ids),
> +	},
> +	.probe = lpc32xx_pwm_probe,
> +	.remove = __devexit_p(lpc32xx_pwm_remove),
> +};
> +module_platform_driver(lpc32xx_pwm_driver);
> +
> +MODULE_ALIAS("platform:lpc32xx-pwm");
> +MODULE_AUTHOR("Alexandre Pereira da Silva <aletes.xgr-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>");
> +MODULE_DESCRIPTION("LPC32XX PWM Driver");
> +MODULE_LICENSE("GPL v2");
> -- 
> 1.7.10
> 
> 
> 

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