Re: [PATCH v3 2/3] pwm: iproc: Add support for Broadcom iproc pwm controller

[Scott Branden <scott.branden@broadcom.com>]

Hi Dhananjaya,

One minor comment inline.

On 16-06-20 07:14 AM, Yendapally Reddy Dhananjaya Reddy wrote:
> Add support for the PWM controller present in Broadcom's iProc
> family of SoCs. This driver is derived from the pwm-bcm-kona
> driver, with changes to the register offsets and bit positions.
> It has been tested on the  Northstar+ bcm958625HR board.
>
> Signed-off-by: Yendapally Reddy Dhananjaya Reddy <yendapally.reddy@broadcom.com>
> ---
>   drivers/pwm/Kconfig         |  10 ++
>   drivers/pwm/Makefile        |   1 +
>   drivers/pwm/pwm-bcm-iproc.c | 327 ++++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 338 insertions(+)
>   create mode 100644 drivers/pwm/pwm-bcm-iproc.c
>
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> index c182efc..d298ebd 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -74,6 +74,16 @@ config PWM_ATMEL_TCB
>   	  To compile this driver as a module, choose M here: the module
>   	  will be called pwm-atmel-tcb.
>
> +config PWM_BCM_IPROC
> +	tristate "iProc PWM support"
> +	depends on ARCH_BCM_IPROC
depends on ARCH_BCM_IPROC || COMPILE_TEST
> +	help
> +	  Generic PWM framework driver for Broadcom iProc PWM block. This
> +	  block is used in Broadcom iProc SoC's.
> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called pwm-bcm-iproc.
> +
>   config PWM_BCM_KONA
>   	tristate "Kona PWM support"
>   	depends on ARCH_BCM_MOBILE
> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
> index dd35bc1..a196d79 100644
> --- a/drivers/pwm/Makefile
> +++ b/drivers/pwm/Makefile
> @@ -4,6 +4,7 @@ obj-$(CONFIG_PWM_AB8500)	+= pwm-ab8500.o
>   obj-$(CONFIG_PWM_ATMEL)		+= pwm-atmel.o
>   obj-$(CONFIG_PWM_ATMEL_HLCDC_PWM)	+= pwm-atmel-hlcdc.o
>   obj-$(CONFIG_PWM_ATMEL_TCB)	+= pwm-atmel-tcb.o
> +obj-$(CONFIG_PWM_BCM_IPROC)	+= pwm-bcm-iproc.o
>   obj-$(CONFIG_PWM_BCM_KONA)	+= pwm-bcm-kona.o
>   obj-$(CONFIG_PWM_BCM2835)	+= pwm-bcm2835.o
>   obj-$(CONFIG_PWM_BERLIN)	+= pwm-berlin.o
> diff --git a/drivers/pwm/pwm-bcm-iproc.c b/drivers/pwm/pwm-bcm-iproc.c
> new file mode 100644
> index 0000000..952c457
> --- /dev/null
> +++ b/drivers/pwm/pwm-bcm-iproc.c
> @@ -0,0 +1,327 @@
> +/*
> + * Copyright (C) 2016 Broadcom
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License as
> + * published by the Free Software Foundation version 2.
> + *
> + * This program is distributed "as is" WITHOUT ANY WARRANTY of any
> + * kind, whether express or implied; without even the implied warranty
> + * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/math64.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/pwm.h>
> +
> +#define IPROC_PWM_CTRL_OFFSET			(0x00)
> +#define IPROC_PWM_CTRL_TYPE_SHIFT(chan)		(15 + (chan))
> +#define IPROC_PWM_CTRL_POLARITY_SHIFT(chan)	(8 + (chan))
> +#define IPROC_PWM_CTRL_EN_SHIFT(chan)		(chan)
> +
> +#define IPROC_PWM_PERIOD_OFFSET(chan)		(0x04 + ((chan) << 3))
> +#define IPROC_PWM_PERIOD_MIN			(0x02)
> +#define IPROC_PWM_PERIOD_MAX			(0xffff)
> +
> +#define IPROC_PWM_DUTY_CYCLE_OFFSET(chan)	(0x08 + ((chan) << 3))
> +#define IPROC_PWM_DUTY_CYCLE_MIN		(0x00)
> +#define IPROC_PWM_DUTY_CYCLE_MAX		(0xffff)
> +
> +#define IPROC_PWM_PRESCALE_OFFSET		(0x24)
> +#define IPROC_PWM_PRESCALE_BITS			(0x06)
> +#define IPROC_PWM_PRESCALE_SHIFT(chan)		((3 - (chan)) *	\
> +						IPROC_PWM_PRESCALE_BITS)
> +#define IPROC_PWM_PRESCALE_MASK(chan)		(IPROC_PWM_PRESCALE_MAX << \
> +						IPROC_PWM_PRESCALE_SHIFT(chan))
> +#define IPROC_PWM_PRESCALE_MIN			(0x00)
> +#define IPROC_PWM_PRESCALE_MAX			(0x3f)
> +
> +#define IPROC_PWM_CHANNEL_COUNT			(0x04)
> +
> +struct iproc_pwmc {
> +	struct pwm_chip chip;
> +	void __iomem *base;
> +	struct clk *clk;
> +};
> +
> +static inline struct iproc_pwmc *to_iproc_pwmc(struct pwm_chip *_chip)
> +{
> +	return container_of(_chip, struct iproc_pwmc, chip);
> +}
> +
> +static void iproc_pwmc_unset_enable_bit(struct iproc_pwmc *ip, u32 chan)
> +{
> +	unsigned int value = readl(ip->base + IPROC_PWM_CTRL_OFFSET);
> +
> +	value &= ~(1 << IPROC_PWM_CTRL_EN_SHIFT(chan));
> +	writel(value, ip->base + IPROC_PWM_CTRL_OFFSET);
> +
> +	/*
> +	 * There must be a min 400ns delay between clearing trigger and setting
> +	 * it. Failing to do this may result in no PWM signal.
> +	 */
> +	ndelay(400);
> +}
> +
> +static void iproc_pwmc_set_enable_bit(struct iproc_pwmc *ip, unsigned int chan)
> +{
> +	unsigned int value = readl(ip->base + IPROC_PWM_CTRL_OFFSET);
> +
> +	/* Set trigger bit to apply new settings */
> +	value |= 1 << IPROC_PWM_CTRL_EN_SHIFT(chan);
> +	writel(value, ip->base + IPROC_PWM_CTRL_OFFSET);
> +
> +	/* Trigger bit must be held high for at least 400 ns. */
> +	ndelay(400);
> +}
> +
> +static int iproc_pwmc_config(struct pwm_chip *chip, struct pwm_device *pwm,
> +			     int duty_ns, int period_ns, bool config_apply)
> +{
> +	unsigned long prescale = IPROC_PWM_PRESCALE_MIN;
> +	struct iproc_pwmc *ip = to_iproc_pwmc(chip);
> +	unsigned int value, chan = pwm->hwpwm;
> +	unsigned long period_cnt, duty_cnt;
> +	u64 val, div, rate;
> +
> +	rate = clk_get_rate(ip->clk);
> +	if (!rate) {
> +		dev_err(pwm->chip->dev, "pwm clock has no frequency\n");
> +		return -EINVAL;
> +	}
> +
> +	/*
> +	 * Find period count, duty count and prescale to suit duty_ns and
> +	 * period_ns. This is done according to formulas described below:
> +	 *
> +	 * period_ns = 10^9 * (PRESCALE + 1) * PC / PWM_CLK_RATE
> +	 * duty_ns = 10^9 * (PRESCALE + 1) * DC / PWM_CLK_RATE
> +	 *
> +	 * PC = (PWM_CLK_RATE * period_ns) / (10^9 * (PRESCALE + 1))
> +	 * DC = (PWM_CLK_RATE * duty_ns) / (10^9 * (PRESCALE + 1))
> +	 */
> +	while (1) {
> +		div = 1000000000;
> +		div *= 1 + prescale;
> +		val = rate * period_ns;
> +		period_cnt = div64_u64(val, div);
> +		val = rate * duty_ns;
> +		duty_cnt = div64_u64(val, div);
> +
> +		if (period_cnt < IPROC_PWM_PERIOD_MIN ||
> +				duty_cnt < IPROC_PWM_DUTY_CYCLE_MIN)
> +			return -EINVAL;
> +
> +		if (period_cnt <= IPROC_PWM_PERIOD_MAX &&
> +				 duty_cnt <= IPROC_PWM_DUTY_CYCLE_MAX)
> +			break;
> +
> +		/* Otherwise, increase prescale and recalculate counts */
> +		if (++prescale > IPROC_PWM_PRESCALE_MAX)
> +			return -EINVAL;
> +	}
> +
> +	/*
> +	 * Don't apply settings if disabled. The period and duty cycle are
> +	 * always calculated above to ensure the new values are
> +	 * validated immediately instead of on enable.
> +	 */
> +	if (pwm_is_enabled(pwm) || config_apply) {
> +		iproc_pwmc_unset_enable_bit(ip, chan);
> +
> +		value = readl(ip->base + IPROC_PWM_PRESCALE_OFFSET);
> +		value &= ~IPROC_PWM_PRESCALE_MASK(chan);
> +		value |= prescale << IPROC_PWM_PRESCALE_SHIFT(chan);
> +
> +		writel(value, ip->base + IPROC_PWM_PRESCALE_OFFSET);
> +		writel(period_cnt, ip->base + IPROC_PWM_PERIOD_OFFSET(chan));
> +		writel(duty_cnt, ip->base + IPROC_PWM_DUTY_CYCLE_OFFSET(chan));
> +
> +		iproc_pwmc_set_enable_bit(ip, chan);
> +	}
> +
> +	return 0;
> +}
> +
> +static int iproc_pwmc_set_polarity(struct pwm_chip *chip,
> +				   struct pwm_device *pwm,
> +				   enum pwm_polarity polarity)
> +{
> +	struct iproc_pwmc *ip = to_iproc_pwmc(chip);
> +	unsigned int chan = pwm->hwpwm;
> +	unsigned int value;
> +	int ret;
> +
> +	ret = clk_prepare_enable(ip->clk);
> +	if (ret < 0) {
> +		dev_err(chip->dev, "failed to enable clock: %d\n", ret);
> +		return ret;
> +	}
> +
> +	iproc_pwmc_unset_enable_bit(ip, chan);
> +
> +	value = readl(ip->base + IPROC_PWM_CTRL_OFFSET);
> +	if (polarity == PWM_POLARITY_NORMAL)
> +		value |= 1 << IPROC_PWM_CTRL_POLARITY_SHIFT(chan);
> +	else
> +		value &= ~(1 << IPROC_PWM_CTRL_POLARITY_SHIFT(chan));
> +	writel(value, ip->base + IPROC_PWM_CTRL_OFFSET);
> +
> +	iproc_pwmc_set_enable_bit(ip, chan);
> +
> +	clk_disable_unprepare(ip->clk);
> +
> +	return 0;
> +}
> +
> +static int iproc_pwmc_enable(struct pwm_chip *chip, struct pwm_device *pwm)
> +{
> +	struct iproc_pwmc *ip = to_iproc_pwmc(chip);
> +	int ret;
> +
> +	ret = clk_prepare_enable(ip->clk);
> +	if (ret < 0) {
> +		dev_err(chip->dev, "failed to enable clock: %d\n", ret);
> +		return ret;
> +	}
> +
> +	ret = iproc_pwmc_config(chip, pwm, pwm_get_duty_cycle(pwm),
> +					pwm_get_period(pwm), true);
> +	if (ret < 0) {
> +		clk_disable_unprepare(ip->clk);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static void iproc_pwmc_disable(struct pwm_chip *chip, struct pwm_device *pwm)
> +{
> +	struct iproc_pwmc *ip = to_iproc_pwmc(chip);
> +	unsigned int chan = pwm->hwpwm;
> +	unsigned int value;
> +
> +	iproc_pwmc_unset_enable_bit(ip, chan);
> +
> +	writel(0, ip->base + IPROC_PWM_DUTY_CYCLE_OFFSET(chan));
> +	writel(0, ip->base + IPROC_PWM_PERIOD_OFFSET(chan));
> +
> +	/* Set prescale to 0 for this channel */
> +	value = readl(ip->base + IPROC_PWM_PRESCALE_OFFSET);
> +	value &= ~IPROC_PWM_PRESCALE_MASK(chan);
> +	writel(value, ip->base + IPROC_PWM_PRESCALE_OFFSET);
> +
> +	iproc_pwmc_set_enable_bit(ip, chan);
> +
> +	clk_disable_unprepare(ip->clk);
> +}
> +
> +static int iproc_pwmc_config_check(struct pwm_chip *chip,
> +				    struct pwm_device *pwm,
> +				    int duty_ns, int period_ns)
> +{
> +	return iproc_pwmc_config(chip, pwm, duty_ns, period_ns, false);
> +}
> +
> +static const struct pwm_ops iproc_pwm_ops = {
> +	.config = iproc_pwmc_config_check,
> +	.set_polarity = iproc_pwmc_set_polarity,
> +	.enable = iproc_pwmc_enable,
> +	.disable = iproc_pwmc_disable,
> +	.owner = THIS_MODULE,
> +};
> +
> +static int iproc_pwmc_probe(struct platform_device *pdev)
> +{
> +	struct iproc_pwmc *ip;
> +	struct resource *res;
> +	unsigned int value;
> +	unsigned int chan;
> +	int ret;
> +
> +	ip = devm_kzalloc(&pdev->dev, sizeof(*ip), GFP_KERNEL);
> +	if (ip == NULL)
> +		return -ENOMEM;
> +
> +	platform_set_drvdata(pdev, ip);
> +
> +	ip->chip.dev = &pdev->dev;
> +	ip->chip.ops = &iproc_pwm_ops;
> +	ip->chip.base = -1;
> +	ip->chip.npwm = IPROC_PWM_CHANNEL_COUNT;
> +	ip->chip.of_xlate = of_pwm_xlate_with_flags;
> +	ip->chip.of_pwm_n_cells = 3;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	ip->base = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(ip->base))
> +		return PTR_ERR(ip->base);
> +
> +	ip->clk = devm_clk_get(&pdev->dev, NULL);
> +	if (IS_ERR(ip->clk)) {
> +		dev_err(&pdev->dev, "failed to get clock: %ld\n",
> +			PTR_ERR(ip->clk));
> +		return PTR_ERR(ip->clk);
> +	}
> +
> +	ret = clk_prepare_enable(ip->clk);
> +	if (ret < 0) {
> +		dev_err(&pdev->dev, "failed to enable clock: %d\n", ret);
> +		return ret;
> +	}
> +
> +	/* Set full drive and normal polarity for all channels */
> +	value = readl(ip->base + IPROC_PWM_CTRL_OFFSET);
> +	for (chan = 0; chan < ip->chip.npwm; chan++) {
> +		value &= ~(1 << IPROC_PWM_CTRL_TYPE_SHIFT(chan));
> +		value |= 1 << IPROC_PWM_CTRL_POLARITY_SHIFT(chan);
> +	}
> +	writel(value, ip->base + IPROC_PWM_CTRL_OFFSET);
> +
> +	clk_disable_unprepare(ip->clk);
> +
> +	ret = pwmchip_add(&ip->chip);
> +	if (ret < 0)
> +		dev_err(&pdev->dev, "failed to add PWM chip: %d\n", ret);
> +
> +	return ret;
> +}
> +
> +static int iproc_pwmc_remove(struct platform_device *pdev)
> +{
> +	struct iproc_pwmc *ip = platform_get_drvdata(pdev);
> +	unsigned int chan;
> +
> +	for (chan = 0; chan < ip->chip.npwm; chan++)
> +		if (pwm_is_enabled(&ip->chip.pwms[chan]))
> +			clk_disable_unprepare(ip->clk);
> +
> +	return pwmchip_remove(&ip->chip);
> +}
> +
> +static const struct of_device_id bcm_iproc_pwmc_dt[] = {
> +	{ .compatible = "brcm,iproc-pwm" },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, bcm_iproc_pwmc_dt);
> +
> +static struct platform_driver iproc_pwmc_driver = {
> +	.driver = {
> +		.name = "bcm-iproc-pwm",
> +		.of_match_table = bcm_iproc_pwmc_dt,
> +	},
> +	.probe = iproc_pwmc_probe,
> +	.remove = iproc_pwmc_remove,
> +};
> +module_platform_driver(iproc_pwmc_driver);
> +
> +MODULE_AUTHOR("Broadcom Corporation");
> +MODULE_DESCRIPTION("Broadcom iProc PWM driver");
> +MODULE_LICENSE("GPL v2");
>