drivers/pwm/pwm-visconti.c

   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 <nobuhiro1.iwamatsu@toshiba.co.jp>
   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
  36 struct visconti_pwm_chip {
  37         struct pwm_chip chip;
  38         void __iomem *base;
  39 };
  40
  41 static inline struct visconti_pwm_chip *visconti_pwm_from_chip(struct pwm_chip *chip)
  42 {
  43         return container_of(chip, struct visconti_pwm_chip, chip);
  44 }
  45
  46 static int visconti_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
  47                               const struct pwm_state *state)
  48 {
  49         struct visconti_pwm_chip *priv = visconti_pwm_from_chip(chip);
  50         u32 period, duty_cycle, pwmc0;
  51
  52         if (!state->enabled) {
  53                 writel(0, priv->base + PIPGM_PCSR(pwm->hwpwm));
  54                 return 0;
  55         }
  56
  57         /*
  58          * The biggest period the hardware can provide is
  59          *      (0xffff << 3) * 1000 ns
  60          * This value fits easily in an u32, so simplify the maths by
  61          * capping the values to 32 bit integers.
  62          */
  63         if (state->period > (0xffff << 3) * 1000)
  64                 period = (0xffff << 3) * 1000;
  65         else
  66                 period = state->period;
  67
  68         if (state->duty_cycle > period)
  69                 duty_cycle = period;
  70         else
  71                 duty_cycle = state->duty_cycle;
  72
  73         /*
  74          * The input clock runs fixed at 1 MHz, so we have only
  75          * microsecond resolution and so can divide by
  76          * NSEC_PER_SEC / CLKFREQ = 1000 without losing precision.
  77          */
  78         period /= 1000;
  79         duty_cycle /= 1000;
  80
  81         if (!period)
  82                 return -ERANGE;
  83
  84         /*
  85          * PWMC controls a divider that divides the input clk by a power of two
  86          * between 1 and 8. As a smaller divider yields higher precision, pick
  87          * the smallest possible one. As period is at most 0xffff << 3, pwmc0 is
  88          * in the intended range [0..3].
  89          */
  90         pwmc0 = fls(period >> 16);
  91         if (WARN_ON(pwmc0 > 3))
  92                 return -EINVAL;
  93
  94         period >>= pwmc0;
  95         duty_cycle >>= pwmc0;
  96
  97         if (state->polarity == PWM_POLARITY_INVERSED)
  98                 pwmc0 |= PIPGM_PWMC_PWMACT;
  99         writel(pwmc0, priv->base + PIPGM_PWMC(pwm->hwpwm));
 100         writel(duty_cycle, priv->base + PIPGM_PDUT(pwm->hwpwm));
 101         writel(period, priv->base + PIPGM_PCSR(pwm->hwpwm));
 102
 103         return 0;
 104 }
 105
 106 static int visconti_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 107                                   struct pwm_state *state)
 108 {
 109         struct visconti_pwm_chip *priv = visconti_pwm_from_chip(chip);
 110         u32 period, duty, pwmc0, pwmc0_clk;
 111
 112         period = readl(priv->base + PIPGM_PCSR(pwm->hwpwm));
 113         duty = readl(priv->base + PIPGM_PDUT(pwm->hwpwm));
 114         pwmc0 = readl(priv->base + PIPGM_PWMC(pwm->hwpwm));
 115         pwmc0_clk = pwmc0 & PIPGM_PWMC_CLK_MASK;
 116
 117         state->period = (period << pwmc0_clk) * NSEC_PER_USEC;
 118         state->duty_cycle = (duty << pwmc0_clk) * NSEC_PER_USEC;
 119         if (pwmc0 & PIPGM_PWMC_POLARITY_MASK)
 120                 state->polarity = PWM_POLARITY_INVERSED;
 121         else
 122                 state->polarity = PWM_POLARITY_NORMAL;
 123
 124         state->enabled = true;
 125
 126         return 0;
 127 }
 128
 129 static const struct pwm_ops visconti_pwm_ops = {
 130         .apply = visconti_pwm_apply,
 131         .get_state = visconti_pwm_get_state,
 132         .owner = THIS_MODULE,
 133 };
 134
 135 static int visconti_pwm_probe(struct platform_device *pdev)
 136 {
 137         struct device *dev = &pdev->dev;
 138         struct visconti_pwm_chip *priv;
 139         int ret;
 140
 141         priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 142         if (!priv)
 143                 return -ENOMEM;
 144
 145         priv->base = devm_platform_ioremap_resource(pdev, 0);
 146         if (IS_ERR(priv->base))
 147                 return PTR_ERR(priv->base);
 148
 149         priv->chip.dev = dev;
 150         priv->chip.ops = &visconti_pwm_ops;
 151         priv->chip.npwm = 4;
 152
 153         ret = devm_pwmchip_add(&pdev->dev, &priv->chip);
 154         if (ret < 0)
 155                 return dev_err_probe(&pdev->dev, ret, "Cannot register visconti PWM\n");
 156
 157         return 0;
 158 }
 159
 160 static const struct of_device_id visconti_pwm_of_match[] = {
 161         { .compatible = "toshiba,visconti-pwm", },
 162         { }
 163 };
 164 MODULE_DEVICE_TABLE(of, visconti_pwm_of_match);
 165
 166 static struct platform_driver visconti_pwm_driver = {
 167         .driver = {
 168                 .name = "pwm-visconti",
 169                 .of_match_table = visconti_pwm_of_match,
 170         },
 171         .probe = visconti_pwm_probe,
 172 };
 173 module_platform_driver(visconti_pwm_driver);
 174
 175 MODULE_LICENSE("GPL v2");
 176 MODULE_AUTHOR("Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>");
 177 MODULE_ALIAS("platform:pwm-visconti");