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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Toshiba Visconti pulse-width-modulation controller driver
4 *
5 * Copyright (c) 2020 - 2021 TOSHIBA CORPORATION
6 * Copyright (c) 2020 - 2021 Toshiba Electronic Devices & Storage Corporation
7 *
8 * Authors: Nobuhiro Iwamatsu <[email protected]>
9 *
10 * Limitations:
11 * - The fixed input clock is running at 1 MHz and is divided by either 1,
12 * 2, 4 or 8.
13 * - When the settings of the PWM are modified, the new values are shadowed
14 * in hardware until the PIPGM_PCSR register is written and the currently
15 * running period is completed. This way the hardware switches atomically
16 * from the old setting to the new.
17 * - Disabling the hardware completes the currently running period and keeps
18 * the output at low level at all times.
19 */
20
21#include <linux/err.h>
22#include <linux/io.h>
23#include <linux/module.h>
24#include <linux/of.h>
25#include <linux/platform_device.h>
26#include <linux/pwm.h>
27
28#define PIPGM_PCSR(ch) (0x400 + 4 * (ch))
29#define PIPGM_PDUT(ch) (0x420 + 4 * (ch))
30#define PIPGM_PWMC(ch) (0x440 + 4 * (ch))
31
32#define PIPGM_PWMC_PWMACT BIT(5)
33#define PIPGM_PWMC_CLK_MASK GENMASK(1, 0)
34#define PIPGM_PWMC_POLARITY_MASK GENMASK(5, 5)
35
36struct visconti_pwm_chip {
37 void __iomem *base;
38};
39
40static inline struct visconti_pwm_chip *visconti_pwm_from_chip(struct pwm_chip *chip)
41{
42 return pwmchip_get_drvdata(chip);
43}
44
45static int visconti_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
46 const struct pwm_state *state)
47{
48 struct visconti_pwm_chip *priv = visconti_pwm_from_chip(chip);
49 u32 period, duty_cycle, pwmc0;
50
51 if (!state->enabled) {
52 writel(0, priv->base + PIPGM_PCSR(pwm->hwpwm));
53 return 0;
54 }
55
56 /*
57 * The biggest period the hardware can provide is
58 * (0xffff << 3) * 1000 ns
59 * This value fits easily in an u32, so simplify the maths by
60 * capping the values to 32 bit integers.
61 */
62 if (state->period > (0xffff << 3) * 1000)
63 period = (0xffff << 3) * 1000;
64 else
65 period = state->period;
66
67 if (state->duty_cycle > period)
68 duty_cycle = period;
69 else
70 duty_cycle = state->duty_cycle;
71
72 /*
73 * The input clock runs fixed at 1 MHz, so we have only
74 * microsecond resolution and so can divide by
75 * NSEC_PER_SEC / CLKFREQ = 1000 without losing precision.
76 */
77 period /= 1000;
78 duty_cycle /= 1000;
79
80 if (!period)
81 return -ERANGE;
82
83 /*
84 * PWMC controls a divider that divides the input clk by a power of two
85 * between 1 and 8. As a smaller divider yields higher precision, pick
86 * the smallest possible one. As period is at most 0xffff << 3, pwmc0 is
87 * in the intended range [0..3].
88 */
89 pwmc0 = fls(period >> 16);
90 if (WARN_ON(pwmc0 > 3))
91 return -EINVAL;
92
93 period >>= pwmc0;
94 duty_cycle >>= pwmc0;
95
96 if (state->polarity == PWM_POLARITY_INVERSED)
97 pwmc0 |= PIPGM_PWMC_PWMACT;
98 writel(pwmc0, priv->base + PIPGM_PWMC(pwm->hwpwm));
99 writel(duty_cycle, priv->base + PIPGM_PDUT(pwm->hwpwm));
100 writel(period, priv->base + PIPGM_PCSR(pwm->hwpwm));
101
102 return 0;
103}
104
105static int visconti_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
106 struct pwm_state *state)
107{
108 struct visconti_pwm_chip *priv = visconti_pwm_from_chip(chip);
109 u32 period, duty, pwmc0, pwmc0_clk;
110
111 period = readl(priv->base + PIPGM_PCSR(pwm->hwpwm));
112 duty = readl(priv->base + PIPGM_PDUT(pwm->hwpwm));
113 pwmc0 = readl(priv->base + PIPGM_PWMC(pwm->hwpwm));
114 pwmc0_clk = pwmc0 & PIPGM_PWMC_CLK_MASK;
115
116 state->period = (period << pwmc0_clk) * NSEC_PER_USEC;
117 state->duty_cycle = (duty << pwmc0_clk) * NSEC_PER_USEC;
118 if (pwmc0 & PIPGM_PWMC_POLARITY_MASK)
119 state->polarity = PWM_POLARITY_INVERSED;
120 else
121 state->polarity = PWM_POLARITY_NORMAL;
122
123 state->enabled = true;
124
125 return 0;
126}
127
128static const struct pwm_ops visconti_pwm_ops = {
129 .apply = visconti_pwm_apply,
130 .get_state = visconti_pwm_get_state,
131};
132
133static int visconti_pwm_probe(struct platform_device *pdev)
134{
135 struct device *dev = &pdev->dev;
136 struct pwm_chip *chip;
137 struct visconti_pwm_chip *priv;
138 int ret;
139
140 chip = devm_pwmchip_alloc(dev, 4, sizeof(*priv));
141 if (IS_ERR(chip))
142 return PTR_ERR(chip);
143 priv = visconti_pwm_from_chip(chip);
144
145 priv->base = devm_platform_ioremap_resource(pdev, 0);
146 if (IS_ERR(priv->base))
147 return PTR_ERR(priv->base);
148
149 chip->ops = &visconti_pwm_ops;
150
151 ret = devm_pwmchip_add(&pdev->dev, chip);
152 if (ret < 0)
153 return dev_err_probe(&pdev->dev, ret, "Cannot register visconti PWM\n");
154
155 return 0;
156}
157
158static const struct of_device_id visconti_pwm_of_match[] = {
159 { .compatible = "toshiba,visconti-pwm" },
160 { }
161};
162MODULE_DEVICE_TABLE(of, visconti_pwm_of_match);
163
164static struct platform_driver visconti_pwm_driver = {
165 .driver = {
166 .name = "pwm-visconti",
167 .of_match_table = visconti_pwm_of_match,
168 },
169 .probe = visconti_pwm_probe,
170};
171module_platform_driver(visconti_pwm_driver);
172
173MODULE_DESCRIPTION("Toshiba Visconti Pulse Width Modulator driver");
174MODULE_LICENSE("GPL v2");
175MODULE_AUTHOR("Nobuhiro Iwamatsu <[email protected]>");
176MODULE_ALIAS("platform:pwm-visconti");