pwm-imx.c

/*
 * simple driver for PWM (Pulse Width Modulator) controller
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Derived from pxa PWM driver by eric miao <eric.miao@marvell.com>
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/io.h>
#include <linux/pwm.h>
#include <linux/of.h>
#include <linux/of_device.h>

/* i.MX1 and i.MX21 share the same PWM function block: */

#define MX1_PWMC			0x00   /* PWM Control Register */
#define MX1_PWMS			0x04   /* PWM Sample Register */
#define MX1_PWMP			0x08   /* PWM Period Register */

#define MX1_PWMC_EN			(1 << 4)

/* i.MX27, i.MX31, i.MX35 share the same PWM function block: */

#define MX3_PWMCR			0x00    /* PWM Control Register */
#define MX3_PWMSR			0x04    /* PWM Status Register */
#define MX3_PWMSAR			0x0C    /* PWM Sample Register */
#define MX3_PWMPR			0x10    /* PWM Period Register */
#define MX3_PWMCR_PRESCALER(x)		((((x) - 1) & 0xFFF) << 4)
#define MX3_PWMCR_DOZEEN		(1 << 24)
#define MX3_PWMCR_WAITEN		(1 << 23)
#define MX3_PWMCR_DBGEN			(1 << 22)
#define MX3_PWMCR_POUTC			(1 << 18)
#define MX3_PWMCR_CLKSRC_IPG_HIGH	(2 << 16)
#define MX3_PWMCR_CLKSRC_IPG		(1 << 16)
#define MX3_PWMCR_SWR			(1 << 3)
#define MX3_PWMCR_EN			(1 << 0)
#define MX3_PWMSR_FIFOAV_4WORDS		0x4
#define MX3_PWMSR_FIFOAV_MASK		0x7

#define MX3_PWM_SWR_LOOP		5

struct imx_chip {
	struct clk	*clk_per;

	void __iomem	*mmio_base;

	struct pwm_chip	chip;
};

#define to_imx_chip(chip)	container_of(chip, struct imx_chip, chip)

static int imx_pwm_config_v1(struct pwm_chip *chip,
		struct pwm_device *pwm, int duty_ns, int period_ns)
{
	struct imx_chip *imx = to_imx_chip(chip);

	/*
	 * The PWM subsystem allows for exact frequencies. However,
	 * I cannot connect a scope on my device to the PWM line and
	 * thus cannot provide the program the PWM controller
	 * exactly. Instead, I'm relying on the fact that the
	 * Bootloader (u-boot or WinCE+haret) has programmed the PWM
	 * function group already. So I'll just modify the PWM sample
	 * register to follow the ratio of duty_ns vs. period_ns
	 * accordingly.
	 *
	 * This is good enough for programming the brightness of
	 * the LCD backlight.
	 *
	 * The real implementation would divide PERCLK[0] first by
	 * both the prescaler (/1 .. /128) and then by CLKSEL
	 * (/2 .. /16).
	 */
	u32 max = readl(imx->mmio_base + MX1_PWMP);
	u32 p = max * duty_ns / period_ns;
	writel(max - p, imx->mmio_base + MX1_PWMS);

	return 0;
}

static int imx_pwm_enable_v1(struct pwm_chip *chip, struct pwm_device *pwm)
{
	struct imx_chip *imx = to_imx_chip(chip);
	u32 val;
	int ret;

	ret = clk_prepare_enable(imx->clk_per);
	if (ret < 0)
		return ret;

	val = readl(imx->mmio_base + MX1_PWMC);
	val |= MX1_PWMC_EN;
	writel(val, imx->mmio_base + MX1_PWMC);

	return 0;
}

static void imx_pwm_disable_v1(struct pwm_chip *chip, struct pwm_device *pwm)
{
	struct imx_chip *imx = to_imx_chip(chip);
	u32 val;

	val = readl(imx->mmio_base + MX1_PWMC);
	val &= ~MX1_PWMC_EN;
	writel(val, imx->mmio_base + MX1_PWMC);

	clk_disable_unprepare(imx->clk_per);
}

static void imx_pwm_sw_reset(struct pwm_chip *chip)
{
	struct imx_chip *imx = to_imx_chip(chip);
	struct device *dev = chip->dev;
	int wait_count = 0;
	u32 cr;

	writel(MX3_PWMCR_SWR, imx->mmio_base + MX3_PWMCR);
	do {
		usleep_range(200, 1000);
		cr = readl(imx->mmio_base + MX3_PWMCR);
	} while ((cr & MX3_PWMCR_SWR) &&
		 (wait_count++ < MX3_PWM_SWR_LOOP));

	if (cr & MX3_PWMCR_SWR)
		dev_warn(dev, "software reset timeout\n");
}

static void imx_pwm_wait_fifo_slot(struct pwm_chip *chip,
				   struct pwm_device *pwm)
{
	struct imx_chip *imx = to_imx_chip(chip);
	struct device *dev = chip->dev;
	unsigned int period_ms;
	int fifoav;
	u32 sr;

	sr = readl(imx->mmio_base + MX3_PWMSR);
	fifoav = sr & MX3_PWMSR_FIFOAV_MASK;
	if (fifoav == MX3_PWMSR_FIFOAV_4WORDS) {
		period_ms = DIV_ROUND_UP(pwm_get_period(pwm),
					 NSEC_PER_MSEC);
		msleep(period_ms);

		sr = readl(imx->mmio_base + MX3_PWMSR);
		if (fifoav == (sr & MX3_PWMSR_FIFOAV_MASK))
			dev_warn(dev, "there is no free FIFO slot\n");
	}
}

static int imx_pwm_apply_v2(struct pwm_chip *chip, struct pwm_device *pwm,
			    struct pwm_state *state)
{
	unsigned long period_cycles, duty_cycles, prescale;
	struct imx_chip *imx = to_imx_chip(chip);
	struct pwm_state cstate;
	unsigned long long c;
	int ret;
	u32 cr;

	pwm_get_state(pwm, &cstate);

	if (state->enabled) {
		c = clk_get_rate(imx->clk_per);
		c *= state->period;

		do_div(c, 1000000000);
		period_cycles = c;

		prescale = period_cycles / 0x10000 + 1;

		period_cycles /= prescale;
		c = (unsigned long long)period_cycles * state->duty_cycle;
		do_div(c, state->period);
		duty_cycles = c;

		/*
		 * according to imx pwm RM, the real period value should be
		 * PERIOD value in PWMPR plus 2.
		 */
		if (period_cycles > 2)
			period_cycles -= 2;
		else
			period_cycles = 0;

		/*
		 * Wait for a free FIFO slot if the PWM is already enabled, and
		 * flush the FIFO if the PWM was disabled and is about to be
		 * enabled.
		 */
		if (cstate.enabled) {
			imx_pwm_wait_fifo_slot(chip, pwm);
		} else {
			ret = clk_prepare_enable(imx->clk_per);
			if (ret)
				return ret;

			imx_pwm_sw_reset(chip);
		}

		writel(duty_cycles, imx->mmio_base + MX3_PWMSAR);
		writel(period_cycles, imx->mmio_base + MX3_PWMPR);

		cr = MX3_PWMCR_PRESCALER(prescale) |
		     MX3_PWMCR_DOZEEN | MX3_PWMCR_WAITEN |
		     MX3_PWMCR_DBGEN | MX3_PWMCR_CLKSRC_IPG_HIGH |
		     MX3_PWMCR_EN;

		if (state->polarity == PWM_POLARITY_INVERSED)
			cr |= MX3_PWMCR_POUTC;

		writel(cr, imx->mmio_base + MX3_PWMCR);
	} else if (cstate.enabled) {
		writel(0, imx->mmio_base + MX3_PWMCR);

		clk_disable_unprepare(imx->clk_per);
	}

	return 0;
}

static const struct pwm_ops imx_pwm_ops_v1 = {
	.enable = imx_pwm_enable_v1,
	.disable = imx_pwm_disable_v1,
	.config = imx_pwm_config_v1,
	.owner = THIS_MODULE,
};

static const struct pwm_ops imx_pwm_ops_v2 = {
	.apply = imx_pwm_apply_v2,
	.owner = THIS_MODULE,
};

struct imx_pwm_data {
	bool polarity_supported;
	const struct pwm_ops *ops;
};

static struct imx_pwm_data imx_pwm_data_v1 = {
	.ops = &imx_pwm_ops_v1,
};

static struct imx_pwm_data imx_pwm_data_v2 = {
	.polarity_supported = true,
	.ops = &imx_pwm_ops_v2,
};

static const struct of_device_id imx_pwm_dt_ids[] = {
	{ .compatible = "fsl,imx1-pwm", .data = &imx_pwm_data_v1, },
	{ .compatible = "fsl,imx27-pwm", .data = &imx_pwm_data_v2, },
	{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, imx_pwm_dt_ids);

static int imx_pwm_probe(struct platform_device *pdev)
{
	const struct of_device_id *of_id =
			of_match_device(imx_pwm_dt_ids, &pdev->dev);
	const struct imx_pwm_data *data;
	struct imx_chip *imx;
	struct resource *r;
	int ret = 0;

	if (!of_id)
		return -ENODEV;

	data = of_id->data;

	imx = devm_kzalloc(&pdev->dev, sizeof(*imx), GFP_KERNEL);
	if (imx == NULL)
		return -ENOMEM;

	imx->clk_per = devm_clk_get(&pdev->dev, "per");
	if (IS_ERR(imx->clk_per)) {
		dev_err(&pdev->dev, "getting per clock failed with %ld\n",
				PTR_ERR(imx->clk_per));
		return PTR_ERR(imx->clk_per);
	}

	imx->chip.ops = data->ops;
	imx->chip.dev = &pdev->dev;
	imx->chip.base = -1;
	imx->chip.npwm = 1;

	if (data->polarity_supported) {
		dev_dbg(&pdev->dev, "PWM supports output inversion\n");
		imx->chip.of_xlate = of_pwm_xlate_with_flags;
		imx->chip.of_pwm_n_cells = 3;
	}

	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	imx->mmio_base = devm_ioremap_resource(&pdev->dev, r);
	if (IS_ERR(imx->mmio_base))
		return PTR_ERR(imx->mmio_base);

	ret = pwmchip_add(&imx->chip);
	if (ret < 0)
		return ret;

	platform_set_drvdata(pdev, imx);
	return 0;
}

static int imx_pwm_remove(struct platform_device *pdev)
{
	struct imx_chip *imx;

	imx = platform_get_drvdata(pdev);
	if (imx == NULL)
		return -ENODEV;

	return pwmchip_remove(&imx->chip);
}

static struct platform_driver imx_pwm_driver = {
	.driver		= {
		.name	= "imx-pwm",
		.of_match_table = imx_pwm_dt_ids,
	},
	.probe		= imx_pwm_probe,
	.remove		= imx_pwm_remove,
};

module_platform_driver(imx_pwm_driver);

MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");