diff options
Diffstat (limited to 'drivers/pwm/pwm-sifive.c')
-rw-r--r-- | drivers/pwm/pwm-sifive.c | 353 |
1 files changed, 353 insertions, 0 deletions
diff --git a/drivers/pwm/pwm-sifive.c b/drivers/pwm/pwm-sifive.c new file mode 100644 index 000000000..393a4b97f --- /dev/null +++ b/drivers/pwm/pwm-sifive.c @@ -0,0 +1,353 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2017-2018 SiFive + * For SiFive's PWM IP block documentation please refer Chapter 14 of + * Reference Manual : https://static.dev.sifive.com/FU540-C000-v1.0.pdf + * + * Limitations: + * - When changing both duty cycle and period, we cannot prevent in + * software that the output might produce a period with mixed + * settings (new period length and old duty cycle). + * - The hardware cannot generate a 100% duty cycle. + * - The hardware generates only inverted output. + */ +#include <linux/clk.h> +#include <linux/io.h> +#include <linux/module.h> +#include <linux/platform_device.h> +#include <linux/pwm.h> +#include <linux/slab.h> +#include <linux/bitfield.h> + +/* Register offsets */ +#define PWM_SIFIVE_PWMCFG 0x0 +#define PWM_SIFIVE_PWMCOUNT 0x8 +#define PWM_SIFIVE_PWMS 0x10 +#define PWM_SIFIVE_PWMCMP(i) (0x20 + 4 * (i)) + +/* PWMCFG fields */ +#define PWM_SIFIVE_PWMCFG_SCALE GENMASK(3, 0) +#define PWM_SIFIVE_PWMCFG_STICKY BIT(8) +#define PWM_SIFIVE_PWMCFG_ZERO_CMP BIT(9) +#define PWM_SIFIVE_PWMCFG_DEGLITCH BIT(10) +#define PWM_SIFIVE_PWMCFG_EN_ALWAYS BIT(12) +#define PWM_SIFIVE_PWMCFG_EN_ONCE BIT(13) +#define PWM_SIFIVE_PWMCFG_CENTER BIT(16) +#define PWM_SIFIVE_PWMCFG_GANG BIT(24) +#define PWM_SIFIVE_PWMCFG_IP BIT(28) + +#define PWM_SIFIVE_CMPWIDTH 16 +#define PWM_SIFIVE_DEFAULT_PERIOD 10000000 + +struct pwm_sifive_ddata { + struct pwm_chip chip; + struct mutex lock; /* lock to protect user_count and approx_period */ + struct notifier_block notifier; + struct clk *clk; + void __iomem *regs; + unsigned int real_period; + unsigned int approx_period; + int user_count; +}; + +static inline +struct pwm_sifive_ddata *pwm_sifive_chip_to_ddata(struct pwm_chip *c) +{ + return container_of(c, struct pwm_sifive_ddata, chip); +} + +static int pwm_sifive_request(struct pwm_chip *chip, struct pwm_device *pwm) +{ + struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip); + + mutex_lock(&ddata->lock); + ddata->user_count++; + mutex_unlock(&ddata->lock); + + return 0; +} + +static void pwm_sifive_free(struct pwm_chip *chip, struct pwm_device *pwm) +{ + struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip); + + mutex_lock(&ddata->lock); + ddata->user_count--; + mutex_unlock(&ddata->lock); +} + +/* Called holding ddata->lock */ +static void pwm_sifive_update_clock(struct pwm_sifive_ddata *ddata, + unsigned long rate) +{ + unsigned long long num; + unsigned long scale_pow; + int scale; + u32 val; + /* + * The PWM unit is used with pwmzerocmp=0, so the only way to modify the + * period length is using pwmscale which provides the number of bits the + * counter is shifted before being feed to the comparators. A period + * lasts (1 << (PWM_SIFIVE_CMPWIDTH + pwmscale)) clock ticks. + * (1 << (PWM_SIFIVE_CMPWIDTH + scale)) * 10^9/rate = period + */ + scale_pow = div64_ul(ddata->approx_period * (u64)rate, NSEC_PER_SEC); + scale = clamp(ilog2(scale_pow) - PWM_SIFIVE_CMPWIDTH, 0, 0xf); + + val = PWM_SIFIVE_PWMCFG_EN_ALWAYS | + FIELD_PREP(PWM_SIFIVE_PWMCFG_SCALE, scale); + writel(val, ddata->regs + PWM_SIFIVE_PWMCFG); + + /* As scale <= 15 the shift operation cannot overflow. */ + num = (unsigned long long)NSEC_PER_SEC << (PWM_SIFIVE_CMPWIDTH + scale); + ddata->real_period = div64_ul(num, rate); + dev_dbg(ddata->chip.dev, + "New real_period = %u ns\n", ddata->real_period); +} + +static int pwm_sifive_get_state(struct pwm_chip *chip, struct pwm_device *pwm, + struct pwm_state *state) +{ + struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip); + u32 duty, val; + + duty = readl(ddata->regs + PWM_SIFIVE_PWMCMP(pwm->hwpwm)); + + state->enabled = duty > 0; + + val = readl(ddata->regs + PWM_SIFIVE_PWMCFG); + if (!(val & PWM_SIFIVE_PWMCFG_EN_ALWAYS)) + state->enabled = false; + + state->period = ddata->real_period; + state->duty_cycle = + (u64)duty * ddata->real_period >> PWM_SIFIVE_CMPWIDTH; + state->polarity = PWM_POLARITY_INVERSED; + + return 0; +} + +static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm, + const struct pwm_state *state) +{ + struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip); + struct pwm_state cur_state; + unsigned int duty_cycle; + unsigned long long num; + bool enabled; + int ret = 0; + u32 frac; + + if (state->polarity != PWM_POLARITY_INVERSED) + return -EINVAL; + + cur_state = pwm->state; + enabled = cur_state.enabled; + + duty_cycle = state->duty_cycle; + if (!state->enabled) + duty_cycle = 0; + + /* + * The problem of output producing mixed setting as mentioned at top, + * occurs here. To minimize the window for this problem, we are + * calculating the register values first and then writing them + * consecutively + */ + num = (u64)duty_cycle * (1U << PWM_SIFIVE_CMPWIDTH); + frac = DIV64_U64_ROUND_CLOSEST(num, state->period); + /* The hardware cannot generate a 100% duty cycle */ + frac = min(frac, (1U << PWM_SIFIVE_CMPWIDTH) - 1); + + mutex_lock(&ddata->lock); + if (state->period != ddata->approx_period) { + /* + * Don't let a 2nd user change the period underneath the 1st user. + * However if ddate->approx_period == 0 this is the first time we set + * any period, so let whoever gets here first set the period so other + * users who agree on the period won't fail. + */ + if (ddata->user_count != 1 && ddata->approx_period) { + mutex_unlock(&ddata->lock); + return -EBUSY; + } + ddata->approx_period = state->period; + pwm_sifive_update_clock(ddata, clk_get_rate(ddata->clk)); + } + mutex_unlock(&ddata->lock); + + /* + * If the PWM is enabled the clk is already on. So only enable it + * conditionally to have it on exactly once afterwards independent of + * the PWM state. + */ + if (!enabled) { + ret = clk_enable(ddata->clk); + if (ret) { + dev_err(ddata->chip.dev, "Enable clk failed\n"); + return ret; + } + } + + writel(frac, ddata->regs + PWM_SIFIVE_PWMCMP(pwm->hwpwm)); + + if (!state->enabled) + clk_disable(ddata->clk); + + return 0; +} + +static const struct pwm_ops pwm_sifive_ops = { + .request = pwm_sifive_request, + .free = pwm_sifive_free, + .get_state = pwm_sifive_get_state, + .apply = pwm_sifive_apply, + .owner = THIS_MODULE, +}; + +static int pwm_sifive_clock_notifier(struct notifier_block *nb, + unsigned long event, void *data) +{ + struct clk_notifier_data *ndata = data; + struct pwm_sifive_ddata *ddata = + container_of(nb, struct pwm_sifive_ddata, notifier); + + if (event == POST_RATE_CHANGE) { + mutex_lock(&ddata->lock); + pwm_sifive_update_clock(ddata, ndata->new_rate); + mutex_unlock(&ddata->lock); + } + + return NOTIFY_OK; +} + +static int pwm_sifive_probe(struct platform_device *pdev) +{ + struct device *dev = &pdev->dev; + struct pwm_sifive_ddata *ddata; + struct pwm_chip *chip; + int ret; + u32 val; + unsigned int enabled_pwms = 0, enabled_clks = 1; + + ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL); + if (!ddata) + return -ENOMEM; + + mutex_init(&ddata->lock); + chip = &ddata->chip; + chip->dev = dev; + chip->ops = &pwm_sifive_ops; + chip->npwm = 4; + + ddata->regs = devm_platform_ioremap_resource(pdev, 0); + if (IS_ERR(ddata->regs)) + return PTR_ERR(ddata->regs); + + ddata->clk = devm_clk_get(dev, NULL); + if (IS_ERR(ddata->clk)) + return dev_err_probe(dev, PTR_ERR(ddata->clk), + "Unable to find controller clock\n"); + + ret = clk_prepare_enable(ddata->clk); + if (ret) { + dev_err(dev, "failed to enable clock for pwm: %d\n", ret); + return ret; + } + + val = readl(ddata->regs + PWM_SIFIVE_PWMCFG); + if (val & PWM_SIFIVE_PWMCFG_EN_ALWAYS) { + unsigned int i; + + for (i = 0; i < chip->npwm; ++i) { + val = readl(ddata->regs + PWM_SIFIVE_PWMCMP(i)); + if (val > 0) + ++enabled_pwms; + } + } + + /* The clk should be on once for each running PWM. */ + if (enabled_pwms) { + while (enabled_clks < enabled_pwms) { + /* This is not expected to fail as the clk is already on */ + ret = clk_enable(ddata->clk); + if (unlikely(ret)) { + dev_err_probe(dev, ret, "Failed to enable clk\n"); + goto disable_clk; + } + ++enabled_clks; + } + } else { + clk_disable(ddata->clk); + enabled_clks = 0; + } + + /* Watch for changes to underlying clock frequency */ + ddata->notifier.notifier_call = pwm_sifive_clock_notifier; + ret = clk_notifier_register(ddata->clk, &ddata->notifier); + if (ret) { + dev_err(dev, "failed to register clock notifier: %d\n", ret); + goto disable_clk; + } + + ret = pwmchip_add(chip); + if (ret < 0) { + dev_err(dev, "cannot register PWM: %d\n", ret); + goto unregister_clk; + } + + platform_set_drvdata(pdev, ddata); + dev_dbg(dev, "SiFive PWM chip registered %d PWMs\n", chip->npwm); + + return 0; + +unregister_clk: + clk_notifier_unregister(ddata->clk, &ddata->notifier); +disable_clk: + while (enabled_clks) { + clk_disable(ddata->clk); + --enabled_clks; + } + clk_unprepare(ddata->clk); + + return ret; +} + +static int pwm_sifive_remove(struct platform_device *dev) +{ + struct pwm_sifive_ddata *ddata = platform_get_drvdata(dev); + struct pwm_device *pwm; + int ch; + + pwmchip_remove(&ddata->chip); + clk_notifier_unregister(ddata->clk, &ddata->notifier); + + for (ch = 0; ch < ddata->chip.npwm; ch++) { + pwm = &ddata->chip.pwms[ch]; + if (pwm->state.enabled) + clk_disable(ddata->clk); + } + + clk_unprepare(ddata->clk); + + return 0; +} + +static const struct of_device_id pwm_sifive_of_match[] = { + { .compatible = "sifive,pwm0" }, + {}, +}; +MODULE_DEVICE_TABLE(of, pwm_sifive_of_match); + +static struct platform_driver pwm_sifive_driver = { + .probe = pwm_sifive_probe, + .remove = pwm_sifive_remove, + .driver = { + .name = "pwm-sifive", + .of_match_table = pwm_sifive_of_match, + }, +}; +module_platform_driver(pwm_sifive_driver); + +MODULE_DESCRIPTION("SiFive PWM driver"); +MODULE_LICENSE("GPL v2"); |