pwm: Add support for Broadcom iProc PWM controller

Add support for the PWM controller present in Broadcom's iProc family of
SoCs. It has been tested on the Northstar+ bcm958625HR board.

Signed-off-by: Yendapally Reddy Dhananjaya Reddy <[e-mail]>
[[e-mail]: bunch of coding style fixes, cleanups]
Signed-off-by: Thierry Reding <[e-mail]>

drivers/pwm/Kconfig

···
 	  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
+	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

drivers/pwm/Makefile

···
 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

drivers/pwm/pwm-bcm-iproc.c

···
+/*
+ * 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(ch)		(15 + (ch))
+#define IPROC_PWM_CTRL_POLARITY_SHIFT(ch)	(8 + (ch))
+#define IPROC_PWM_CTRL_EN_SHIFT(ch)		(ch)
+
+#define IPROC_PWM_PERIOD_OFFSET(ch)		(0x04 + ((ch) << 3))
+#define IPROC_PWM_PERIOD_MIN			0x02
+#define IPROC_PWM_PERIOD_MAX			0xffff
+
+#define IPROC_PWM_DUTY_CYCLE_OFFSET(ch)		(0x08 + ((ch) << 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(ch)		((3 - (ch)) * \
+						 IPROC_PWM_PRESCALE_BITS)
+#define IPROC_PWM_PRESCALE_MASK(ch)		(IPROC_PWM_PRESCALE_MAX << \
+						 IPROC_PWM_PRESCALE_SHIFT(ch))
+#define IPROC_PWM_PRESCALE_MIN			0x00
+#define IPROC_PWM_PRESCALE_MAX			0x3f
+
+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_enable(struct iproc_pwmc *ip, unsigned int channel)
+{
+	u32 value;
+
+	value = readl(ip->base + IPROC_PWM_CTRL_OFFSET);
+	value |= 1 << IPROC_PWM_CTRL_EN_SHIFT(channel);
+	writel(value, ip->base + IPROC_PWM_CTRL_OFFSET);
+
+	/* must be a 400 ns delay between clearing and setting enable bit */
+	ndelay(400);
+}
+
+static void iproc_pwmc_disable(struct iproc_pwmc *ip, unsigned int channel)
+{
+	u32 value;
+
+	value = readl(ip->base + IPROC_PWM_CTRL_OFFSET);
+	value &= ~(1 << IPROC_PWM_CTRL_EN_SHIFT(channel));
+	writel(value, ip->base + IPROC_PWM_CTRL_OFFSET);
+
+	/* must be a 400 ns delay between clearing and setting enable bit */
+	ndelay(400);
+}
+
+static void iproc_pwmc_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+				 struct pwm_state *state)
+{
+	struct iproc_pwmc *ip = to_iproc_pwmc(chip);
+	u64 tmp, multi, rate;
+	u32 value, prescale;
+
+	rate = clk_get_rate(ip->clk);
+
+	value = readl(ip->base + IPROC_PWM_CTRL_OFFSET);
+
+	if (value & BIT(IPROC_PWM_CTRL_EN_SHIFT(pwm->hwpwm)))
+		state->enabled = true;
+	else
+		state->enabled = false;
+
+	if (value & BIT(IPROC_PWM_CTRL_POLARITY_SHIFT(pwm->hwpwm)))
+		state->polarity = PWM_POLARITY_NORMAL;
+	else
+		state->polarity = PWM_POLARITY_INVERSED;
+
+	value = readl(ip->base + IPROC_PWM_PRESCALE_OFFSET);
+	prescale = value >> IPROC_PWM_PRESCALE_SHIFT(pwm->hwpwm);
+	prescale &= IPROC_PWM_PRESCALE_MAX;
+
+	multi = NSEC_PER_SEC * (prescale + 1);
+
+	value = readl(ip->base + IPROC_PWM_PERIOD_OFFSET(pwm->hwpwm));
+	tmp = (value & IPROC_PWM_PERIOD_MAX) * multi;
+	state->period = div64_u64(tmp, rate);
+
+	value = readl(ip->base + IPROC_PWM_DUTY_CYCLE_OFFSET(pwm->hwpwm));
+	tmp = (value & IPROC_PWM_PERIOD_MAX) * multi;
+	state->duty_cycle = div64_u64(tmp, rate);
+}
+
+static int iproc_pwmc_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			    struct pwm_state *state)
+{
+	unsigned long prescale = IPROC_PWM_PRESCALE_MIN;
+	struct iproc_pwmc *ip = to_iproc_pwmc(chip);
+	u32 value, period, duty;
+	u64 rate;
+
+	rate = clk_get_rate(ip->clk);
+
+	/*
+	 * Find period count, duty count and prescale to suit duty_cycle and
+	 * period. 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) {
+		u64 value, div;
+
+		div = NSEC_PER_SEC * (prescale + 1);
+		value = rate * state->period;
+		period = div64_u64(value, div);
+		value = rate * state->duty_cycle;
+		duty = div64_u64(value, div);
+
+		if (period < IPROC_PWM_PERIOD_MIN ||
+		    duty < IPROC_PWM_DUTY_CYCLE_MIN)
+			return -EINVAL;
+
+		if (period <= IPROC_PWM_PERIOD_MAX &&
+		     duty <= IPROC_PWM_DUTY_CYCLE_MAX)
+			break;
+
+		/* Otherwise, increase prescale and recalculate counts */
+		if (++prescale > IPROC_PWM_PRESCALE_MAX)
+			return -EINVAL;
+	}
+
+	iproc_pwmc_disable(ip, pwm->hwpwm);
+
+	/* Set prescale */
+	value = readl(ip->base + IPROC_PWM_PRESCALE_OFFSET);
+	value &= ~IPROC_PWM_PRESCALE_MASK(pwm->hwpwm);
+	value |= prescale << IPROC_PWM_PRESCALE_SHIFT(pwm->hwpwm);
+	writel(value, ip->base + IPROC_PWM_PRESCALE_OFFSET);
+
+	/* set period and duty cycle */
+	writel(period, ip->base + IPROC_PWM_PERIOD_OFFSET(pwm->hwpwm));
+	writel(duty, ip->base + IPROC_PWM_DUTY_CYCLE_OFFSET(pwm->hwpwm));
+
+	/* set polarity */
+	value = readl(ip->base + IPROC_PWM_CTRL_OFFSET);
+
+	if (state->polarity == PWM_POLARITY_NORMAL)
+		value |= 1 << IPROC_PWM_CTRL_POLARITY_SHIFT(pwm->hwpwm);
+	else
+		value &= ~(1 << IPROC_PWM_CTRL_POLARITY_SHIFT(pwm->hwpwm));
+
+	writel(value, ip->base + IPROC_PWM_CTRL_OFFSET);
+
+	if (state->enabled)
+		iproc_pwmc_enable(ip, pwm->hwpwm);
+
+	return 0;
+}
+
+static const struct pwm_ops iproc_pwm_ops = {
+	.apply = iproc_pwmc_apply,
+	.get_state = iproc_pwmc_get_state,
+};
+
+static int iproc_pwmc_probe(struct platform_device *pdev)
+{
+	struct iproc_pwmc *ip;
+	struct resource *res;
+	unsigned int i;
+	u32 value;
+	int ret;
+
+	ip = devm_kzalloc(&pdev->dev, sizeof(*ip), GFP_KERNEL);
+	if (!ip)
+		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 = 4;
+	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 (i = 0; i < ip->chip.npwm; i++) {
+		value &= ~(1 << IPROC_PWM_CTRL_TYPE_SHIFT(i));
+		value |= 1 << IPROC_PWM_CTRL_POLARITY_SHIFT(i);
+	}
+
+	writel(value, ip->base + IPROC_PWM_CTRL_OFFSET);
+
+	ret = pwmchip_add(&ip->chip);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "failed to add PWM chip: %d\n", ret);
+		clk_disable_unprepare(ip->clk);
+	}
+
+	return ret;
+}
+
+static int iproc_pwmc_remove(struct platform_device *pdev)
+{
+	struct iproc_pwmc *ip = platform_get_drvdata(pdev);
+
+	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("Yendapally Reddy Dhananjaya Reddy <[e-mail]>");
+MODULE_DESCRIPTION("Broadcom iProc PWM driver");
+MODULE_LICENSE("GPL v2");