drivers/pwm/pwm-apple.c

   1 // SPDX-License-Identifier: GPL-2.0 OR MIT
   2 /*
   3  * Driver for the Apple SoC PWM controller
   4  *
   5  * Copyright The Asahi Linux Contributors
   6  *
   7  * Limitations:
   8  * - The writes to cycle registers are shadowed until a write to
   9  *   the control register.
  10  * - If both OFF_CYCLES and ON_CYCLES are set to 0, the output
  11  *   is a constant off signal.
  12  * - When APPLE_PWM_CTRL is set to 0, the output is constant low
  13  */
  14
  15 #include <linux/module.h>
  16 #include <linux/platform_device.h>
  17 #include <linux/pwm.h>
  18 #include <linux/io.h>
  19 #include <linux/clk.h>
  20 #include <linux/math64.h>
  21
  22 #define APPLE_PWM_CTRL        0x00
  23 #define APPLE_PWM_ON_CYCLES   0x1c
  24 #define APPLE_PWM_OFF_CYCLES  0x18
  25
  26 #define APPLE_PWM_CTRL_ENABLE        BIT(0)
  27 #define APPLE_PWM_CTRL_MODE          BIT(2)
  28 #define APPLE_PWM_CTRL_UPDATE        BIT(5)
  29 #define APPLE_PWM_CTRL_TRIGGER       BIT(9)
  30 #define APPLE_PWM_CTRL_INVERT        BIT(10)
  31 #define APPLE_PWM_CTRL_OUTPUT_ENABLE BIT(14)
  32
  33 struct apple_pwm {
  34         struct pwm_chip chip;
  35         void __iomem *base;
  36         u64 clkrate;
  37 };
  38
  39 static inline struct apple_pwm *to_apple_pwm(struct pwm_chip *chip)
  40 {
  41         return container_of(chip, struct apple_pwm, chip);
  42 }
  43
  44 static int apple_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
  45                            const struct pwm_state *state)
  46 {
  47         struct apple_pwm *fpwm;
  48
  49         if (state->polarity == PWM_POLARITY_INVERSED)
  50                 return -EINVAL;
  51
  52         fpwm = to_apple_pwm(chip);
  53         if (state->enabled) {
  54                 u64 on_cycles, off_cycles;
  55
  56                 on_cycles = mul_u64_u64_div_u64(fpwm->clkrate,
  57                                                 state->duty_cycle, NSEC_PER_SEC);
  58                 if (on_cycles > 0xFFFFFFFF)
  59                         on_cycles = 0xFFFFFFFF;
  60
  61                 off_cycles = mul_u64_u64_div_u64(fpwm->clkrate,
  62                                                  state->period, NSEC_PER_SEC) - on_cycles;
  63                 if (off_cycles > 0xFFFFFFFF)
  64                         off_cycles = 0xFFFFFFFF;
  65
  66                 writel(on_cycles, fpwm->base + APPLE_PWM_ON_CYCLES);
  67                 writel(off_cycles, fpwm->base + APPLE_PWM_OFF_CYCLES);
  68                 writel(APPLE_PWM_CTRL_ENABLE | APPLE_PWM_CTRL_OUTPUT_ENABLE | APPLE_PWM_CTRL_UPDATE,
  69                        fpwm->base + APPLE_PWM_CTRL);
  70         } else {
  71                 writel(0, fpwm->base + APPLE_PWM_CTRL);
  72         }
  73         return 0;
  74 }
  75
  76 static int apple_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
  77                            struct pwm_state *state)
  78 {
  79         struct apple_pwm *fpwm;
  80         u32 on_cycles, off_cycles, ctrl;
  81
  82         fpwm = to_apple_pwm(chip);
  83
  84         ctrl = readl(fpwm->base + APPLE_PWM_CTRL);
  85         on_cycles = readl(fpwm->base + APPLE_PWM_ON_CYCLES);
  86         off_cycles = readl(fpwm->base + APPLE_PWM_OFF_CYCLES);
  87
  88         state->enabled = (ctrl & APPLE_PWM_CTRL_ENABLE) && (ctrl & APPLE_PWM_CTRL_OUTPUT_ENABLE);
  89         state->polarity = PWM_POLARITY_NORMAL;
  90         // on_cycles + off_cycles is 33 bits, NSEC_PER_SEC is 30, there is no overflow
  91         state->duty_cycle = DIV64_U64_ROUND_UP((u64)on_cycles * NSEC_PER_SEC, fpwm->clkrate);
  92         state->period = DIV64_U64_ROUND_UP(((u64)off_cycles + (u64)on_cycles) *
  93                                             NSEC_PER_SEC, fpwm->clkrate);
  94
  95         return 0;
  96 }
  97
  98 static const struct pwm_ops apple_pwm_ops = {
  99         .apply = apple_pwm_apply,
 100         .get_state = apple_pwm_get_state,
 101         .owner = THIS_MODULE,
 102 };
 103
 104 static int apple_pwm_probe(struct platform_device *pdev)
 105 {
 106         struct apple_pwm *fpwm;
 107         struct clk *clk;
 108         int ret;
 109
 110         fpwm = devm_kzalloc(&pdev->dev, sizeof(*fpwm), GFP_KERNEL);
 111         if (!fpwm)
 112                 return -ENOMEM;
 113
 114         fpwm->base = devm_platform_ioremap_resource(pdev, 0);
 115         if (IS_ERR(fpwm->base))
 116                 return PTR_ERR(fpwm->base);
 117
 118         clk = devm_clk_get_enabled(&pdev->dev, NULL);
 119         if (IS_ERR(clk))
 120                 return dev_err_probe(&pdev->dev, PTR_ERR(clk), "unable to get the clock");
 121
 122         /*
 123          * Uses the 24MHz system clock on all existing devices, can only
 124          * happen if the device tree is broken
 125          *
 126          * This check is done to prevent an overflow in .apply
 127          */
 128         fpwm->clkrate = clk_get_rate(clk);
 129         if (fpwm->clkrate > NSEC_PER_SEC)
 130                 return dev_err_probe(&pdev->dev, -EINVAL, "pwm clock out of range");
 131
 132         fpwm->chip.dev = &pdev->dev;
 133         fpwm->chip.npwm = 1;
 134         fpwm->chip.ops = &apple_pwm_ops;
 135
 136         ret = devm_pwmchip_add(&pdev->dev, &fpwm->chip);
 137         if (ret < 0)
 138                 return dev_err_probe(&pdev->dev, ret, "unable to add pwm chip");
 139
 140         return 0;
 141 }
 142
 143 static const struct of_device_id apple_pwm_of_match[] = {
 144         { .compatible = "apple,s5l-fpwm" },
 145         {}
 146 };
 147 MODULE_DEVICE_TABLE(of, apple_pwm_of_match);
 148
 149 static struct platform_driver apple_pwm_driver = {
 150         .probe = apple_pwm_probe,
 151         .driver = {
 152                 .name = "apple-pwm",
 153                 .of_match_table = apple_pwm_of_match,
 154         },
 155 };
 156 module_platform_driver(apple_pwm_driver);
 157
 158 MODULE_DESCRIPTION("Apple SoC PWM driver");
 159 MODULE_LICENSE("Dual MIT/GPL");