[PATCH v2 2/3] pwm: iproc: Add support for Broadcom iproc pwm controller

[Yendapally Reddy Dhananjaya Reddy]

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@xxxxxxxxxxxx>
---
 drivers/pwm/Kconfig         |  10 ++
 drivers/pwm/Makefile        |   1 +
 drivers/pwm/pwm-bcm-iproc.c | 320 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 331 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
+	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..3ba3ca5
--- /dev/null
+++ b/drivers/pwm/pwm-bcm-iproc.c
@@ -0,0 +1,320 @@
+/*
+ * 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)
+{
+	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)) {
+		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));
+	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 const struct pwm_ops iproc_pwm_ops = {
+	.config = iproc_pwmc_config,
+	.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");
-- 
2.1.0