drivers/pwm/pwm-bcm-kona.c

   1 /*
   2  * Copyright (C) 2014 Broadcom Corporation
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License as
   6  * published by the Free Software Foundation version 2.
   7  *
   8  * This program is distributed "as is" WITHOUT ANY WARRANTY of any
   9  * kind, whether express or implied; without even the implied warranty
  10  * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  */
  13
  14 #include <linux/clk.h>
  15 #include <linux/delay.h>
  16 #include <linux/err.h>
  17 #include <linux/io.h>
  18 #include <linux/ioport.h>
  19 #include <linux/math64.h>
  20 #include <linux/module.h>
  21 #include <linux/of.h>
  22 #include <linux/platform_device.h>
  23 #include <linux/pwm.h>
  24 #include <linux/slab.h>
  25 #include <linux/types.h>
  26
  27 /*
  28  * The Kona PWM has some unusual characteristics.  Here are the main points.
  29  *
  30  * 1) There is no disable bit and the hardware docs advise programming a zero
  31  *    duty to achieve output equivalent to that of a normal disable operation.
  32  *
  33  * 2) Changes to prescale, duty, period, and polarity do not take effect until
  34  *    a subsequent rising edge of the trigger bit.
  35  *
  36  * 3) If the smooth bit and trigger bit are both low, the output is a constant
  37  *    high signal.  Otherwise, the earlier waveform continues to be output.
  38  *
  39  * 4) If the smooth bit is set on the rising edge of the trigger bit, output
  40  *    will transition to the new settings on a period boundary (which could be
  41  *    seconds away).  If the smooth bit is clear, new settings will be applied
  42  *    as soon as possible (the hardware always has a 400ns delay).
  43  *
  44  * 5) When the external clock that feeds the PWM is disabled, output is pegged
  45  *    high or low depending on its state at that exact instant.
  46  */
  47
  48 #define PWM_CONTROL_OFFSET                      (0x00000000)
  49 #define PWM_CONTROL_SMOOTH_SHIFT(chan)          (24 + (chan))
  50 #define PWM_CONTROL_TYPE_SHIFT(chan)            (16 + (chan))
  51 #define PWM_CONTROL_POLARITY_SHIFT(chan)        (8 + (chan))
  52 #define PWM_CONTROL_TRIGGER_SHIFT(chan)         (chan)
  53
  54 #define PRESCALE_OFFSET                         (0x00000004)
  55 #define PRESCALE_SHIFT(chan)                    ((chan) << 2)
  56 #define PRESCALE_MASK(chan)                     (0x7 << PRESCALE_SHIFT(chan))
  57 #define PRESCALE_MIN                            (0x00000000)
  58 #define PRESCALE_MAX                            (0x00000007)
  59
  60 #define PERIOD_COUNT_OFFSET(chan)               (0x00000008 + ((chan) << 3))
  61 #define PERIOD_COUNT_MIN                        (0x00000002)
  62 #define PERIOD_COUNT_MAX                        (0x00ffffff)
  63
  64 #define DUTY_CYCLE_HIGH_OFFSET(chan)            (0x0000000c + ((chan) << 3))
  65 #define DUTY_CYCLE_HIGH_MIN                     (0x00000000)
  66 #define DUTY_CYCLE_HIGH_MAX                     (0x00ffffff)
  67
  68 struct kona_pwmc {
  69         struct pwm_chip chip;
  70         void __iomem *base;
  71         struct clk *clk;
  72 };
  73
  74 static inline struct kona_pwmc *to_kona_pwmc(struct pwm_chip *_chip)
  75 {
  76         return container_of(_chip, struct kona_pwmc, chip);
  77 }
  78
  79 static void kona_pwmc_apply_settings(struct kona_pwmc *kp, unsigned int chan)
  80 {
  81         unsigned int value = readl(kp->base + PWM_CONTROL_OFFSET);
  82
  83         /* Clear trigger bit but set smooth bit to maintain old output */
  84         value |= 1 << PWM_CONTROL_SMOOTH_SHIFT(chan);
  85         value &= ~(1 << PWM_CONTROL_TRIGGER_SHIFT(chan));
  86         writel(value, kp->base + PWM_CONTROL_OFFSET);
  87
  88         /* Set trigger bit and clear smooth bit to apply new settings */
  89         value &= ~(1 << PWM_CONTROL_SMOOTH_SHIFT(chan));
  90         value |= 1 << PWM_CONTROL_TRIGGER_SHIFT(chan);
  91         writel(value, kp->base + PWM_CONTROL_OFFSET);
  92 }
  93
  94 static int kona_pwmc_config(struct pwm_chip *chip, struct pwm_device *pwm,
  95                             int duty_ns, int period_ns)
  96 {
  97         struct kona_pwmc *kp = to_kona_pwmc(chip);
  98         u64 val, div, rate;
  99         unsigned long prescale = PRESCALE_MIN, pc, dc;
 100         unsigned int value, chan = pwm->hwpwm;
 101
 102         /*
 103          * Find period count, duty count and prescale to suit duty_ns and
 104          * period_ns. This is done according to formulas described below:
 105          *
 106          * period_ns = 10^9 * (PRESCALE + 1) * PC / PWM_CLK_RATE
 107          * duty_ns = 10^9 * (PRESCALE + 1) * DC / PWM_CLK_RATE
 108          *
 109          * PC = (PWM_CLK_RATE * period_ns) / (10^9 * (PRESCALE + 1))
 110          * DC = (PWM_CLK_RATE * duty_ns) / (10^9 * (PRESCALE + 1))
 111          */
 112
 113         rate = clk_get_rate(kp->clk);
 114
 115         while (1) {
 116                 div = 1000000000;
 117                 div *= 1 + prescale;
 118                 val = rate * period_ns;
 119                 pc = div64_u64(val, div);
 120                 val = rate * duty_ns;
 121                 dc = div64_u64(val, div);
 122
 123                 /* If duty_ns or period_ns are not achievable then return */
 124                 if (pc < PERIOD_COUNT_MIN || dc < DUTY_CYCLE_HIGH_MIN)
 125                         return -EINVAL;
 126
 127                 /* If pc and dc are in bounds, the calculation is done */
 128                 if (pc <= PERIOD_COUNT_MAX && dc <= DUTY_CYCLE_HIGH_MAX)
 129                         break;
 130
 131                 /* Otherwise, increase prescale and recalculate pc and dc */
 132                 if (++prescale > PRESCALE_MAX)
 133                         return -EINVAL;
 134         }
 135
 136         /* If the PWM channel is enabled, write the settings to the HW */
 137         if (test_bit(PWMF_ENABLED, &pwm->flags)) {
 138                 value = readl(kp->base + PRESCALE_OFFSET);
 139                 value &= ~PRESCALE_MASK(chan);
 140                 value |= prescale << PRESCALE_SHIFT(chan);
 141                 writel(value, kp->base + PRESCALE_OFFSET);
 142
 143                 writel(pc, kp->base + PERIOD_COUNT_OFFSET(chan));
 144
 145                 writel(dc, kp->base + DUTY_CYCLE_HIGH_OFFSET(chan));
 146
 147                 kona_pwmc_apply_settings(kp, chan);
 148         }
 149
 150         return 0;
 151 }
 152
 153 static int kona_pwmc_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
 154                                   enum pwm_polarity polarity)
 155 {
 156         struct kona_pwmc *kp = to_kona_pwmc(chip);
 157         unsigned int chan = pwm->hwpwm;
 158         unsigned int value;
 159         int ret;
 160
 161         ret = clk_prepare_enable(kp->clk);
 162         if (ret < 0) {
 163                 dev_err(chip->dev, "failed to enable clock: %d\n", ret);
 164                 return ret;
 165         }
 166
 167         value = readl(kp->base + PWM_CONTROL_OFFSET);
 168
 169         if (polarity == PWM_POLARITY_NORMAL)
 170                 value |= 1 << PWM_CONTROL_POLARITY_SHIFT(chan);
 171         else
 172                 value &= ~(1 << PWM_CONTROL_POLARITY_SHIFT(chan));
 173
 174         writel(value, kp->base + PWM_CONTROL_OFFSET);
 175
 176         kona_pwmc_apply_settings(kp, chan);
 177
 178         /* Wait for waveform to settle before gating off the clock */
 179         ndelay(400);
 180
 181         clk_disable_unprepare(kp->clk);
 182
 183         return 0;
 184 }
 185
 186 static int kona_pwmc_enable(struct pwm_chip *chip, struct pwm_device *pwm)
 187 {
 188         struct kona_pwmc *kp = to_kona_pwmc(chip);
 189         int ret;
 190
 191         ret = clk_prepare_enable(kp->clk);
 192         if (ret < 0) {
 193                 dev_err(chip->dev, "failed to enable clock: %d\n", ret);
 194                 return ret;
 195         }
 196
 197         ret = kona_pwmc_config(chip, pwm, pwm->duty_cycle, pwm->period);
 198         if (ret < 0) {
 199                 clk_disable_unprepare(kp->clk);
 200                 return ret;
 201         }
 202
 203         return 0;
 204 }
 205
 206 static void kona_pwmc_disable(struct pwm_chip *chip, struct pwm_device *pwm)
 207 {
 208         struct kona_pwmc *kp = to_kona_pwmc(chip);
 209         unsigned int chan = pwm->hwpwm;
 210
 211         /* Simulate a disable by configuring for zero duty */
 212         writel(0, kp->base + DUTY_CYCLE_HIGH_OFFSET(chan));
 213         kona_pwmc_apply_settings(kp, chan);
 214
 215         /* Wait for waveform to settle before gating off the clock */
 216         ndelay(400);
 217
 218         clk_disable_unprepare(kp->clk);
 219 }
 220
 221 static const struct pwm_ops kona_pwm_ops = {
 222         .config = kona_pwmc_config,
 223         .set_polarity = kona_pwmc_set_polarity,
 224         .enable = kona_pwmc_enable,
 225         .disable = kona_pwmc_disable,
 226         .owner = THIS_MODULE,
 227 };
 228
 229 static int kona_pwmc_probe(struct platform_device *pdev)
 230 {
 231         struct kona_pwmc *kp;
 232         struct resource *res;
 233         unsigned int chan;
 234         unsigned int value = 0;
 235         int ret = 0;
 236
 237         kp = devm_kzalloc(&pdev->dev, sizeof(*kp), GFP_KERNEL);
 238         if (kp == NULL)
 239                 return -ENOMEM;
 240
 241         platform_set_drvdata(pdev, kp);
 242
 243         kp->chip.dev = &pdev->dev;
 244         kp->chip.ops = &kona_pwm_ops;
 245         kp->chip.base = -1;
 246         kp->chip.npwm = 6;
 247         kp->chip.of_xlate = of_pwm_xlate_with_flags;
 248         kp->chip.of_pwm_n_cells = 3;
 249         kp->chip.can_sleep = true;
 250
 251         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 252         kp->base = devm_ioremap_resource(&pdev->dev, res);
 253         if (IS_ERR(kp->base))
 254                 return PTR_ERR(kp->base);
 255
 256         kp->clk = devm_clk_get(&pdev->dev, NULL);
 257         if (IS_ERR(kp->clk)) {
 258                 dev_err(&pdev->dev, "failed to get clock: %ld\n",
 259                         PTR_ERR(kp->clk));
 260                 return PTR_ERR(kp->clk);
 261         }
 262
 263         ret = clk_prepare_enable(kp->clk);
 264         if (ret < 0) {
 265                 dev_err(&pdev->dev, "failed to enable clock: %d\n", ret);
 266                 return ret;
 267         }
 268
 269         /* Set push/pull for all channels */
 270         for (chan = 0; chan < kp->chip.npwm; chan++)
 271                 value |= (1 << PWM_CONTROL_TYPE_SHIFT(chan));
 272
 273         writel(value, kp->base + PWM_CONTROL_OFFSET);
 274
 275         clk_disable_unprepare(kp->clk);
 276
 277         ret = pwmchip_add_with_polarity(&kp->chip, PWM_POLARITY_INVERSED);
 278         if (ret < 0)
 279                 dev_err(&pdev->dev, "failed to add PWM chip: %d\n", ret);
 280
 281         return ret;
 282 }
 283
 284 static int kona_pwmc_remove(struct platform_device *pdev)
 285 {
 286         struct kona_pwmc *kp = platform_get_drvdata(pdev);
 287         unsigned int chan;
 288
 289         for (chan = 0; chan < kp->chip.npwm; chan++)
 290                 if (test_bit(PWMF_ENABLED, &kp->chip.pwms[chan].flags))
 291                         clk_disable_unprepare(kp->clk);
 292
 293         return pwmchip_remove(&kp->chip);
 294 }
 295
 296 static const struct of_device_id bcm_kona_pwmc_dt[] = {
 297         { .compatible = "brcm,kona-pwm" },
 298         { },
 299 };
 300 MODULE_DEVICE_TABLE(of, bcm_kona_pwmc_dt);
 301
 302 static struct platform_driver kona_pwmc_driver = {
 303         .driver = {
 304                 .name = "bcm-kona-pwm",
 305                 .of_match_table = bcm_kona_pwmc_dt,
 306         },
 307         .probe = kona_pwmc_probe,
 308         .remove = kona_pwmc_remove,
 309 };
 310 module_platform_driver(kona_pwmc_driver);
 311
 312 MODULE_AUTHOR("Broadcom Corporation <bcm-kernel-feedback-list@broadcom.com>");
 313 MODULE_AUTHOR("Tim Kryger <tkryger@broadcom.com>");
 314 MODULE_DESCRIPTION("Broadcom Kona PWM driver");
 315 MODULE_LICENSE("GPL v2");