[resend rfc] pwm: add BCM2835 PWM driver

[Stefan Wahren]

Hi Bart,

if you make a new version of the driver, then it would be helpful to
have a changelog and a version number.
Also never forget the "signed-off-by".

Am 25.04.2014 12:35, schrieb Bart Tanghe:
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> index 22f2f28..2c93109 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -62,6 +62,17 @@ config PWM_ATMEL_TCB
>  	  To compile this driver as a module, choose M here: the module
>  	  will be called pwm-atmel-tcb.
>  
> +config PWM_BCM2835
> +	tristate "BCM2835 PWM support"
> +	depends on MACH_BCM2835 || MACH_BCM2708
> +	help
> +	  PWM framework driver for BCM2835 controller (raspberry pi)
> +
> +	  The pwm core frequency is set on 1Mhz, period above 1000 are
> +	  accepted.

Please add the unit behind 1000.

> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called pwm-bcm2835.
> +
>  config PWM_BFIN
>  	tristate "Blackfin PWM support"
>  	depends on BFIN_GPTIMERS
> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
> index d8906ec..9863590 100644
> --- a/drivers/pwm/Makefile
> +++ b/drivers/pwm/Makefile
> @@ -3,6 +3,7 @@ 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-$(CONFIG_PWM_BCM2835)	+= pwm-bcm2835.o
>  obj-$(CONFIG_PWM_BFIN)		+= pwm-bfin.o
>  obj-$(CONFIG_PWM_EP93XX)	+= pwm-ep93xx.o
>  obj-$(CONFIG_PWM_IMX)		+= pwm-imx.o
> diff --git a/drivers/pwm/pwm-bcm2835.c b/drivers/pwm/pwm-bcm2835.c
> new file mode 100644
> index 0000000..86bdbd1
> --- /dev/null
> +++ b/drivers/pwm/pwm-bcm2835.c
> @@ -0,0 +1,192 @@
> +/*
> + * pwm-bcm2835 driver
> + * Standard raspberry pi (gpio18 - pwm0)
> + *
> + * Copyright (C) 2014 Thomas more
> + *

Please add a short license text here.

> + */
> +
> +#include <linux/clk.h>
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/pwm.h>
> +
> +/*mmio regiser mapping*/
> +
> +#define DUTY			0x14
> +#define PERIOD			0x10
> +#define CHANNEL		0x10
> +
> +#define PWM_ENABLE	0x00000001
> +#define PWM_POLARITY	0x00000010
> +
> +#define MASK_CTL_PWM	0x000000FF
> +#define CTL_PWM		0x00000081
> +
> +#define DRIVER_AUTHOR "Bart Tanghe <bart.tanghe at thomasmore.be>"
> +#define DRIVER_DESC "A bcm2835 pwm driver -raspberry pi development platform"
> +
> +struct bcm2835_pwm_chip {
> +	struct pwm_chip chip;
> +	struct device *dev;
> +	int channel;
> +	int scaler;
> +	void __iomem *mmio_base;
> +};
> +
> +static inline struct bcm2835_pwm_chip *to_bcm2835_pwm_chip(
> +					struct pwm_chip *chip){
> +
> +	return container_of(chip, struct bcm2835_pwm_chip, chip);
> +}
> +
> +static int bcm2835_pwm_config(struct pwm_chip *chip,
> +			      struct pwm_device *pwm,
> +			      int duty_ns, int period_ns){
> +
> +	struct bcm2835_pwm_chip *pc;
> +
> +	pc = container_of(chip, struct bcm2835_pwm_chip, chip);
> +
> +	iowrite32(duty_ns/pc->scaler, pc->mmio_base + DUTY);
> +	iowrite32(period_ns/pc->scaler, pc->mmio_base + PERIOD);
> +
> +	return 0;
> +}
> +
> +static int bcm2835_pwm_enable(struct pwm_chip *chip,
> +			      struct pwm_device *pwm){
> +
> +	struct bcm2835_pwm_chip *pc;
> +
> +	pc = container_of(chip, struct bcm2835_pwm_chip, chip);
> +
> +	iowrite32(ioread32(pc->mmio_base) | PWM_ENABLE, pc->mmio_base);
> +	return 0;
> +}
> +
> +static void bcm2835_pwm_disable(struct pwm_chip *chip,
> +				struct pwm_device *pwm)
> +{
> +	struct bcm2835_pwm_chip *pc;
> +
> +	pc = to_bcm2835_pwm_chip(chip);
> +
> +	iowrite32(ioread32(pc->mmio_base) & ~PWM_ENABLE, pc->mmio_base);
> +}
> +
> +static int bcm2835_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
> +				enum pwm_polarity polarity)
> +{
> +	struct bcm2835_pwm_chip *pc;
> +
> +	pc = to_bcm2835_pwm_chip(chip);
> +
> +	if (polarity == PWM_POLARITY_NORMAL)
> +		iowrite32((ioread32(pc->mmio_base) & ~PWM_POLARITY),
> +						pc->mmio_base);
> +	else if (polarity == PWM_POLARITY_INVERSED)
> +		iowrite32((ioread32(pc->mmio_base) | PWM_POLARITY),
> +						pc->mmio_base);
> +
> +	return 0;
> +}
> +
> +static const struct pwm_ops bcm2835_pwm_ops = {
> +	.config = bcm2835_pwm_config,
> +	.enable = bcm2835_pwm_enable,
> +	.disable = bcm2835_pwm_disable,
> +	.set_polarity = bcm2835_set_polarity,
> +	.owner = THIS_MODULE,
> +};
> +
> +static int bcm2835_pwm_probe(struct platform_device *pdev)
> +{
> +	struct bcm2835_pwm_chip *pwm;
> +
> +	int ret;
> +	struct resource *r;
> +	u32 start, end;
> +	struct clk *clk;
> +
> +	pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);
> +	if (!pwm) {
> +		dev_err(&pdev->dev, "failed to allocate memory\n");
> +		return -ENOMEM;
> +	}
> +
> +	pwm->dev = &pdev->dev;
> +
> +	clk = clk_get(&pdev->dev, NULL);
> +	if (IS_ERR(clk)) {
> +		dev_err(&pdev->dev, "could not find clk: %ld\n", PTR_ERR(clk));

I'm not sure. Shouldn't be the pwm freed at this point?

> +		return PTR_ERR(clk);
> +	}
> +
> +	pwm->scaler = (int)1000000000/clk_get_rate(clk);
> +
> +	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	pwm->mmio_base = devm_ioremap_resource(&pdev->dev, r);
> +	if (IS_ERR(pwm->mmio_base))
> +		return PTR_ERR(pwm->mmio_base);
> +
> +	start = r->start;
> +	end = r->end;
> +
> +	platform_set_drvdata(pdev, pwm);

I think it's better to call this, if nothing can't go wrong anymore
(before last return).

> +
> +	pwm->chip.dev = &pdev->dev;
> +	pwm->chip.ops = &bcm2835_pwm_ops;
> +	pwm->chip.npwm = 2;
> +
> +	ret = pwmchip_add(&pwm->chip);
> +	if (ret < 0) {
> +		dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
> +		goto chip_failed;
> +	}
> +
> +	/*set the pwm0 configuration*/
> +	iowrite32((ioread32(pwm->mmio_base) & ~MASK_CTL_PWM)
> +				| CTL_PWM, pwm->mmio_base);
> +
> +	return 0;
> +
> +chip_failed:
> +	devm_kfree(&pdev->dev, pwm);
> +	return -1;
> +
> +}
> +
> +static int bcm2835_pwm_remove(struct platform_device *pdev)
> +{
> +
> +	struct bcm2835_pwm_chip *pc;
> +	pc  = platform_get_drvdata(pdev);
> +
> +	if (WARN_ON(!pc))
> +		return -ENODEV;
> +
> +	return pwmchip_remove(&pc->chip);
> +}
> +
> +static const struct of_device_id bcm2835_pwm_of_match[] = {
> +	{ .compatible = "rpi,pwm-bcm2835" },

A vendor 'rpi' doesn't exists, this should be 'bcrm'.

> +	{ }
> +};

I think MODULE_DEVICE_TABLE() is missing after the structure.

> +
> +static struct platform_driver bcm2835_pwm_driver = {
> +	.driver = {
> +		.name = "pwm-bcm2835",
> +		.owner = THIS_MODULE,
> +		.of_match_table = bcm2835_pwm_of_match,
> +	},
> +	.probe = bcm2835_pwm_probe,
> +	.remove = bcm2835_pwm_remove,
> +};
> +module_platform_driver(bcm2835_pwm_driver);
> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_AUTHOR(DRIVER_AUTHOR);

Please make use of MODULE_DESCRIPTION since you already have a define
for the description. A binding documentation
(Documentation/devicetree/bindings/pwm/) is still missing.

Kind regards
Stefan Wahren