1/*
  2 * drivers/pwm/pwm-tegra.c
  3 *
  4 * Tegra pulse-width-modulation controller driver
  5 *
  6 * Copyright (c) 2010, NVIDIA Corporation.
  7 * Based on arch/arm/plat-mxc/pwm.c by Sascha Hauer <s.hauer@pengutronix.de>
  8 *
  9 * This program is free software; you can redistribute it and/or modify
 10 * it under the terms of the GNU General Public License as published by
 11 * the Free Software Foundation; either version 2 of the License, or
 12 * (at your option) any later version.
 13 *
 14 * This program is distributed in the hope that it will be useful, but WITHOUT
 15 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 16 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 17 * more details.
 18 *
 19 * You should have received a copy of the GNU General Public License along
 20 * with this program; if not, write to the Free Software Foundation, Inc.,
 21 * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 22 */
 23
 24#include <linux/clk.h>
 25#include <linux/err.h>
 26#include <linux/io.h>
 27#include <linux/module.h>
 28#include <linux/of.h>
 29#include <linux/pwm.h>
 30#include <linux/platform_device.h>
 31#include <linux/slab.h>
 32
 33#define PWM_ENABLE	(1 << 31)
 34#define PWM_DUTY_WIDTH	8
 35#define PWM_DUTY_SHIFT	16
 36#define PWM_SCALE_WIDTH	13
 37#define PWM_SCALE_SHIFT	0
 38
 39#define NUM_PWM 4
 40
 41struct tegra_pwm_chip {
 42	struct pwm_chip		chip;
 43	struct device		*dev;
 44
 45	struct clk		*clk;
 46
 47	void __iomem		*mmio_base;
 48};
 49
 50static inline struct tegra_pwm_chip *to_tegra_pwm_chip(struct pwm_chip *chip)
 51{
 52	return container_of(chip, struct tegra_pwm_chip, chip);
 53}
 54
 55static inline u32 pwm_readl(struct tegra_pwm_chip *chip, unsigned int num)
 56{
 57	return readl(chip->mmio_base + (num << 4));
 58}
 59
 60static inline void pwm_writel(struct tegra_pwm_chip *chip, unsigned int num,
 61			     unsigned long val)
 62{
 63	writel(val, chip->mmio_base + (num << 4));
 64}
 65
 66static int tegra_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
 67			    int duty_ns, int period_ns)
 68{
 69	struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
 70	unsigned long long c;
 71	unsigned long rate, hz;
 72	u32 val = 0;
 73	int err;
 74
 75	/*
 76	 * Convert from duty_ns / period_ns to a fixed number of duty ticks
 77	 * per (1 << PWM_DUTY_WIDTH) cycles and make sure to round to the
 78	 * nearest integer during division.
 79	 */
 80	c = duty_ns * ((1 << PWM_DUTY_WIDTH) - 1) + period_ns / 2;
 81	do_div(c, period_ns);
 82
 83	val = (u32)c << PWM_DUTY_SHIFT;
 84
 85	/*
 86	 * Compute the prescaler value for which (1 << PWM_DUTY_WIDTH)
 87	 * cycles at the PWM clock rate will take period_ns nanoseconds.
 88	 */
 89	rate = clk_get_rate(pc->clk) >> PWM_DUTY_WIDTH;
 90	hz = 1000000000ul / period_ns;
 91
 92	rate = (rate + (hz / 2)) / hz;
 93
 94	/*
 95	 * Since the actual PWM divider is the register's frequency divider
 96	 * field minus 1, we need to decrement to get the correct value to
 97	 * write to the register.
 98	 */
 99	if (rate > 0)
100		rate--;
101
102	/*
103	 * Make sure that the rate will fit in the register's frequency
104	 * divider field.
105	 */
106	if (rate >> PWM_SCALE_WIDTH)
107		return -EINVAL;
108
109	val |= rate << PWM_SCALE_SHIFT;
110
111	/*
112	 * If the PWM channel is disabled, make sure to turn on the clock
113	 * before writing the register. Otherwise, keep it enabled.
114	 */
115	if (!test_bit(PWMF_ENABLED, &pwm->flags)) {
116		err = clk_prepare_enable(pc->clk);
117		if (err < 0)
118			return err;
119	} else
120		val |= PWM_ENABLE;
121
122	pwm_writel(pc, pwm->hwpwm, val);
123
124	/*
125	 * If the PWM is not enabled, turn the clock off again to save power.
126	 */
127	if (!test_bit(PWMF_ENABLED, &pwm->flags))
128		clk_disable_unprepare(pc->clk);
129
130	return 0;
131}
132
133static int tegra_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
134{
135	struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
136	int rc = 0;
137	u32 val;
138
139	rc = clk_prepare_enable(pc->clk);
140	if (rc < 0)
141		return rc;
142
143	val = pwm_readl(pc, pwm->hwpwm);
144	val |= PWM_ENABLE;
145	pwm_writel(pc, pwm->hwpwm, val);
146
147	return 0;
148}
149
150static void tegra_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
151{
152	struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
153	u32 val;
154
155	val = pwm_readl(pc, pwm->hwpwm);
156	val &= ~PWM_ENABLE;
157	pwm_writel(pc, pwm->hwpwm, val);
158
159	clk_disable_unprepare(pc->clk);
160}
161
162static const struct pwm_ops tegra_pwm_ops = {
163	.config = tegra_pwm_config,
164	.enable = tegra_pwm_enable,
165	.disable = tegra_pwm_disable,
166	.owner = THIS_MODULE,
167};
168
169static int tegra_pwm_probe(struct platform_device *pdev)
170{
171	struct tegra_pwm_chip *pwm;
172	struct resource *r;
173	int ret;
174
175	pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);
176	if (!pwm) {
177		dev_err(&pdev->dev, "failed to allocate memory\n");
178		return -ENOMEM;
179	}
180
181	pwm->dev = &pdev->dev;
182
183	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
184	pwm->mmio_base = devm_ioremap_resource(&pdev->dev, r);
185	if (IS_ERR(pwm->mmio_base))
186		return PTR_ERR(pwm->mmio_base);
187
188	platform_set_drvdata(pdev, pwm);
189
190	pwm->clk = devm_clk_get(&pdev->dev, NULL);
191	if (IS_ERR(pwm->clk))
192		return PTR_ERR(pwm->clk);
193
194	pwm->chip.dev = &pdev->dev;
195	pwm->chip.ops = &tegra_pwm_ops;
196	pwm->chip.base = -1;
197	pwm->chip.npwm = NUM_PWM;
198
199	ret = pwmchip_add(&pwm->chip);
200	if (ret < 0) {
201		dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
202		return ret;
203	}
204
205	return 0;
206}
207
208static int tegra_pwm_remove(struct platform_device *pdev)
209{
210	struct tegra_pwm_chip *pc = platform_get_drvdata(pdev);
211	int i;
212
213	if (WARN_ON(!pc))
214		return -ENODEV;
215
216	for (i = 0; i < NUM_PWM; i++) {
217		struct pwm_device *pwm = &pc->chip.pwms[i];
218
219		if (!test_bit(PWMF_ENABLED, &pwm->flags))
220			if (clk_prepare_enable(pc->clk) < 0)
221				continue;
222
223		pwm_writel(pc, i, 0);
224
225		clk_disable_unprepare(pc->clk);
226	}
227
228	return pwmchip_remove(&pc->chip);
229}
230
231static const struct of_device_id tegra_pwm_of_match[] = {
232	{ .compatible = "nvidia,tegra20-pwm" },
233	{ .compatible = "nvidia,tegra30-pwm" },
234	{ }
235};
236
237MODULE_DEVICE_TABLE(of, tegra_pwm_of_match);
238
239static struct platform_driver tegra_pwm_driver = {
240	.driver = {
241		.name = "tegra-pwm",
242		.owner = THIS_MODULE,
243		.of_match_table = tegra_pwm_of_match,
244	},
245	.probe = tegra_pwm_probe,
246	.remove = tegra_pwm_remove,
247};
248
249module_platform_driver(tegra_pwm_driver);
250
251MODULE_LICENSE("GPL");
252MODULE_AUTHOR("NVIDIA Corporation");
253MODULE_ALIAS("platform:tegra-pwm");