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         void __iomem *base;
  38 };
  39
  40 static inline struct visconti_pwm_chip *visconti_pwm_from_chip(struct pwm_chip *chip)
  41 {
  42         return pwmchip_get_drvdata(chip);
  43 }
  44
  45 static 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
 105 static 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
 128 static const struct pwm_ops visconti_pwm_ops = {
 129         .apply = visconti_pwm_apply,
 130         .get_state = visconti_pwm_get_state,
 131 };
 132
 133 static 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
 158 static const struct of_device_id visconti_pwm_of_match[] = {
 159         { .compatible = "toshiba,visconti-pwm", },
 160         { }
 161 };
 162 MODULE_DEVICE_TABLE(of, visconti_pwm_of_match);
 163
 164 static 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 };
 171 module_platform_driver(visconti_pwm_driver);
 172
 173 MODULE_DESCRIPTION("Toshiba Visconti Pulse Width Modulator driver");
 174 MODULE_LICENSE("GPL v2");
 175 MODULE_AUTHOR("Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>");
 176 MODULE_ALIAS("platform:pwm-visconti");