1 files changed, 374 insertions, 0 deletions
diff --git a/drivers/pwm/pwm-sifive.c b/drivers/pwm/pwm-sifive.c
new file mode 100644
index 000000000000..4a07315b0744
--- /dev/null
+++ b/drivers/pwm/pwm-sifive.c
@@ -0,0 +1,374 @@
+// 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
+ *
+ * PWM output inversion: According to the SiFive Reference manual
+ * the output of each comparator is high whenever the value of pwms is
+ * greater than or equal to the corresponding pwmcmpX[Reference Manual].
+ *
+ * Figure 29 in the same manual shows that the pwmcmpXcenter bit is
+ * hard-tied to 0 (XNOR), which effectively inverts the comparison so that
+ * the output goes HIGH when  `pwms < pwmcmpX`.
+ *
+ * In other words, each pwmcmp register actually defines the **inactive**
+ * (low) period of the pulse, not the active time exactly opposite to what
+ * the documentation text implies.
+ *
+ * To compensate, this driver always **inverts** the duty value when reading
+ * or writing pwmcmp registers , so that users interact with a conventional
+ * **active-high** PWM interface.
+ *
+ *
+ * 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 0% duty cycle.
+ * - The hardware generates only inverted output.
+ */
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/mod_devicetable.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 device *parent;
+	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 *chip)
+{
+	return pwmchip_get_drvdata(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 = DIV_ROUND_UP_ULL(num, rate);
+	dev_dbg(ddata->parent,
+		"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, inactive;
+
+	inactive = readl(ddata->regs + PWM_SIFIVE_PWMCMP(pwm->hwpwm));
+	/*
+	 * PWM hardware uses 'inactive' counts in pwmcmp, so invert to get actual duty.
+	 * Here, 'inactive' is the low time and we compute duty as max_count - inactive.
+	 */
+	duty = (1U << PWM_SIFIVE_CMPWIDTH) - 1 - inactive;
+
+	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 = DIV_ROUND_UP_ULL((u64)duty * ddata->real_period,
+					     (1U << PWM_SIFIVE_CMPWIDTH));
+	state->polarity = PWM_POLARITY_NORMAL;
+
+	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;
+	u64 frac;
+	u32 inactive;
+
+	if (state->polarity != PWM_POLARITY_NORMAL)
+		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 = num;
+	do_div(frac, state->period);
+	/* The hardware cannot generate a 0% duty cycle */
+	frac = min(frac, (u64)(1U << PWM_SIFIVE_CMPWIDTH) - 1);
+	/* pwmcmp register must be loaded with the inactive(invert the duty) */
+	inactive = (1U << PWM_SIFIVE_CMPWIDTH) - 1 - frac;
+
+	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(pwmchip_parent(chip), "Enable clk failed\n");
+			return ret;
+		}
+	}
+
+	writel(inactive, 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,
+};
+
+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;
+
+	chip = devm_pwmchip_alloc(dev, 4, sizeof(*ddata));
+	if (IS_ERR(chip))
+		return PTR_ERR(chip);
+
+	ddata = pwm_sifive_chip_to_ddata(chip);
+	ddata->parent = dev;
+	mutex_init(&ddata->lock);
+	chip->ops = &pwm_sifive_ops;
+
+	ddata->regs = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(ddata->regs))
+		return PTR_ERR(ddata->regs);
+
+	ddata->clk = devm_clk_get_prepared(dev, NULL);
+	if (IS_ERR(ddata->clk))
+		return dev_err_probe(dev, PTR_ERR(ddata->clk),
+				     "Unable to find controller clock\n");
+
+	ret = clk_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, chip);
+	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;
+	}
+
+	return ret;
+}
+
+static void pwm_sifive_remove(struct platform_device *dev)
+{
+	struct pwm_chip *chip = platform_get_drvdata(dev);
+	struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
+	struct pwm_device *pwm;
+	int ch;
+
+	pwmchip_remove(chip);
+	clk_notifier_unregister(ddata->clk, &ddata->notifier);
+
+	for (ch = 0; ch < chip->npwm; ch++) {
+		pwm = &chip->pwms[ch];
+		if (pwm->state.enabled)
+			clk_disable(ddata->clk);
+	}
+}
+
+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");