1 files changed, 375 insertions, 0 deletions
diff --git a/drivers/pwm/pwm-tegra.c b/drivers/pwm/pwm-tegra.c
new file mode 100644
index 000000000..f3528c56e
--- /dev/null
+++ b/drivers/pwm/pwm-tegra.c
@@ -0,0 +1,375 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * drivers/pwm/pwm-tegra.c
+ *
+ * Tegra pulse-width-modulation controller driver
+ *
+ * Copyright (c) 2010-2020, NVIDIA Corporation.
+ * Based on arch/arm/plat-mxc/pwm.c by Sascha Hauer <s.hauer@pengutronix.de>
+ *
+ * Overview of Tegra Pulse Width Modulator Register:
+ * 1. 13-bit: Frequency division (SCALE)
+ * 2. 8-bit : Pulse division (DUTY)
+ * 3. 1-bit : Enable bit
+ *
+ * The PWM clock frequency is divided by 256 before subdividing it based
+ * on the programmable frequency division value to generate the required
+ * frequency for PWM output. The maximum output frequency that can be
+ * achieved is (max rate of source clock) / 256.
+ * e.g. if source clock rate is 408 MHz, maximum output frequency can be:
+ * 408 MHz/256 = 1.6 MHz.
+ * This 1.6 MHz frequency can further be divided using SCALE value in PWM.
+ *
+ * PWM pulse width: 8 bits are usable [23:16] for varying pulse width.
+ * To achieve 100% duty cycle, program Bit [24] of this register to
+ * 1’b1. In which case the other bits [23:16] are set to don't care.
+ *
+ * Limitations:
+ * -	When PWM is disabled, the output is driven to inactive.
+ * -	It does not allow the current PWM period to complete and
+ *	stops abruptly.
+ *
+ * -	If the register is reconfigured while PWM is running,
+ *	it does not complete the currently running period.
+ *
+ * -	If the user input duty is beyond acceptible limits,
+ *	-EINVAL is returned.
+ */
+
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/pwm.h>
+#include <linux/platform_device.h>
+#include <linux/pinctrl/consumer.h>
+#include <linux/slab.h>
+#include <linux/reset.h>
+
+#define PWM_ENABLE	(1 << 31)
+#define PWM_DUTY_WIDTH	8
+#define PWM_DUTY_SHIFT	16
+#define PWM_SCALE_WIDTH	13
+#define PWM_SCALE_SHIFT	0
+
+struct tegra_pwm_soc {
+	unsigned int num_channels;
+
+	/* Maximum IP frequency for given SoCs */
+	unsigned long max_frequency;
+};
+
+struct tegra_pwm_chip {
+	struct pwm_chip chip;
+	struct device *dev;
+
+	struct clk *clk;
+	struct reset_control*rst;
+
+	unsigned long clk_rate;
+	unsigned long min_period_ns;
+
+	void __iomem *regs;
+
+	const struct tegra_pwm_soc *soc;
+};
+
+static inline struct tegra_pwm_chip *to_tegra_pwm_chip(struct pwm_chip *chip)
+{
+	return container_of(chip, struct tegra_pwm_chip, chip);
+}
+
+static inline u32 pwm_readl(struct tegra_pwm_chip *chip, unsigned int num)
+{
+	return readl(chip->regs + (num << 4));
+}
+
+static inline void pwm_writel(struct tegra_pwm_chip *chip, unsigned int num,
+			     unsigned long val)
+{
+	writel(val, chip->regs + (num << 4));
+}
+
+static int tegra_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
+			    int duty_ns, int period_ns)
+{
+	struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
+	unsigned long long c = duty_ns, hz;
+	unsigned long rate, required_clk_rate;
+	u32 val = 0;
+	int err;
+
+	/*
+	 * Convert from duty_ns / period_ns to a fixed number of duty ticks
+	 * per (1 << PWM_DUTY_WIDTH) cycles and make sure to round to the
+	 * nearest integer during division.
+	 */
+	c *= (1 << PWM_DUTY_WIDTH);
+	c = DIV_ROUND_CLOSEST_ULL(c, period_ns);
+
+	val = (u32)c << PWM_DUTY_SHIFT;
+
+	/*
+	 *  min period = max clock limit >> PWM_DUTY_WIDTH
+	 */
+	if (period_ns < pc->min_period_ns)
+		return -EINVAL;
+
+	/*
+	 * Compute the prescaler value for which (1 << PWM_DUTY_WIDTH)
+	 * cycles at the PWM clock rate will take period_ns nanoseconds.
+	 *
+	 * num_channels: If single instance of PWM controller has multiple
+	 * channels (e.g. Tegra210 or older) then it is not possible to
+	 * configure separate clock rates to each of the channels, in such
+	 * case the value stored during probe will be referred.
+	 *
+	 * If every PWM controller instance has one channel respectively, i.e.
+	 * nums_channels == 1 then only the clock rate can be modified
+	 * dynamically (e.g. Tegra186 or Tegra194).
+	 */
+	if (pc->soc->num_channels == 1) {
+		/*
+		 * Rate is multiplied with 2^PWM_DUTY_WIDTH so that it matches
+		 * with the maximum possible rate that the controller can
+		 * provide. Any further lower value can be derived by setting
+		 * PFM bits[0:12].
+		 *
+		 * required_clk_rate is a reference rate for source clock and
+		 * it is derived based on user requested period. By setting the
+		 * source clock rate as required_clk_rate, PWM controller will
+		 * be able to configure the requested period.
+		 */
+		required_clk_rate = DIV_ROUND_UP_ULL((u64)NSEC_PER_SEC << PWM_DUTY_WIDTH,
+						     period_ns);
+
+		err = clk_set_rate(pc->clk, required_clk_rate);
+		if (err < 0)
+			return -EINVAL;
+
+		/* Store the new rate for further references */
+		pc->clk_rate = clk_get_rate(pc->clk);
+	}
+
+	rate = pc->clk_rate >> PWM_DUTY_WIDTH;
+
+	/* Consider precision in PWM_SCALE_WIDTH rate calculation */
+	hz = DIV_ROUND_CLOSEST_ULL(100ULL * NSEC_PER_SEC, period_ns);
+	rate = DIV_ROUND_CLOSEST_ULL(100ULL * rate, hz);
+
+	/*
+	 * Since the actual PWM divider is the register's frequency divider
+	 * field plus 1, we need to decrement to get the correct value to
+	 * write to the register.
+	 */
+	if (rate > 0)
+		rate--;
+
+	/*
+	 * Make sure that the rate will fit in the register's frequency
+	 * divider field.
+	 */
+	if (rate >> PWM_SCALE_WIDTH)
+		return -EINVAL;
+
+	val |= rate << PWM_SCALE_SHIFT;
+
+	/*
+	 * If the PWM channel is disabled, make sure to turn on the clock
+	 * before writing the register. Otherwise, keep it enabled.
+	 */
+	if (!pwm_is_enabled(pwm)) {
+		err = clk_prepare_enable(pc->clk);
+		if (err < 0)
+			return err;
+	} else
+		val |= PWM_ENABLE;
+
+	pwm_writel(pc, pwm->hwpwm, val);
+
+	/*
+	 * If the PWM is not enabled, turn the clock off again to save power.
+	 */
+	if (!pwm_is_enabled(pwm))
+		clk_disable_unprepare(pc->clk);
+
+	return 0;
+}
+
+static int tegra_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
+	int rc = 0;
+	u32 val;
+
+	rc = clk_prepare_enable(pc->clk);
+	if (rc < 0)
+		return rc;
+
+	val = pwm_readl(pc, pwm->hwpwm);
+	val |= PWM_ENABLE;
+	pwm_writel(pc, pwm->hwpwm, val);
+
+	return 0;
+}
+
+static void tegra_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
+	u32 val;
+
+	val = pwm_readl(pc, pwm->hwpwm);
+	val &= ~PWM_ENABLE;
+	pwm_writel(pc, pwm->hwpwm, val);
+
+	clk_disable_unprepare(pc->clk);
+}
+
+static const struct pwm_ops tegra_pwm_ops = {
+	.config = tegra_pwm_config,
+	.enable = tegra_pwm_enable,
+	.disable = tegra_pwm_disable,
+	.owner = THIS_MODULE,
+};
+
+static int tegra_pwm_probe(struct platform_device *pdev)
+{
+	struct tegra_pwm_chip *pwm;
+	struct resource *r;
+	int ret;
+
+	pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);
+	if (!pwm)
+		return -ENOMEM;
+
+	pwm->soc = of_device_get_match_data(&pdev->dev);
+	pwm->dev = &pdev->dev;
+
+	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	pwm->regs = devm_ioremap_resource(&pdev->dev, r);
+	if (IS_ERR(pwm->regs))
+		return PTR_ERR(pwm->regs);
+
+	platform_set_drvdata(pdev, pwm);
+
+	pwm->clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(pwm->clk))
+		return PTR_ERR(pwm->clk);
+
+	/* Set maximum frequency of the IP */
+	ret = clk_set_rate(pwm->clk, pwm->soc->max_frequency);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "Failed to set max frequency: %d\n", ret);
+		return ret;
+	}
+
+	/*
+	 * The requested and configured frequency may differ due to
+	 * clock register resolutions. Get the configured frequency
+	 * so that PWM period can be calculated more accurately.
+	 */
+	pwm->clk_rate = clk_get_rate(pwm->clk);
+
+	/* Set minimum limit of PWM period for the IP */
+	pwm->min_period_ns =
+	    (NSEC_PER_SEC / (pwm->soc->max_frequency >> PWM_DUTY_WIDTH)) + 1;
+
+	pwm->rst = devm_reset_control_get_exclusive(&pdev->dev, "pwm");
+	if (IS_ERR(pwm->rst)) {
+		ret = PTR_ERR(pwm->rst);
+		dev_err(&pdev->dev, "Reset control is not found: %d\n", ret);
+		return ret;
+	}
+
+	reset_control_deassert(pwm->rst);
+
+	pwm->chip.dev = &pdev->dev;
+	pwm->chip.ops = &tegra_pwm_ops;
+	pwm->chip.base = -1;
+	pwm->chip.npwm = pwm->soc->num_channels;
+
+	ret = pwmchip_add(&pwm->chip);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
+		reset_control_assert(pwm->rst);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int tegra_pwm_remove(struct platform_device *pdev)
+{
+	struct tegra_pwm_chip *pc = platform_get_drvdata(pdev);
+	int err;
+
+	if (WARN_ON(!pc))
+		return -ENODEV;
+
+	err = clk_prepare_enable(pc->clk);
+	if (err < 0)
+		return err;
+
+	reset_control_assert(pc->rst);
+	clk_disable_unprepare(pc->clk);
+
+	return pwmchip_remove(&pc->chip);
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int tegra_pwm_suspend(struct device *dev)
+{
+	return pinctrl_pm_select_sleep_state(dev);
+}
+
+static int tegra_pwm_resume(struct device *dev)
+{
+	return pinctrl_pm_select_default_state(dev);
+}
+#endif
+
+static const struct tegra_pwm_soc tegra20_pwm_soc = {
+	.num_channels = 4,
+	.max_frequency = 48000000UL,
+};
+
+static const struct tegra_pwm_soc tegra186_pwm_soc = {
+	.num_channels = 1,
+	.max_frequency = 102000000UL,
+};
+
+static const struct tegra_pwm_soc tegra194_pwm_soc = {
+	.num_channels = 1,
+	.max_frequency = 408000000UL,
+};
+
+static const struct of_device_id tegra_pwm_of_match[] = {
+	{ .compatible = "nvidia,tegra20-pwm", .data = &tegra20_pwm_soc },
+	{ .compatible = "nvidia,tegra186-pwm", .data = &tegra186_pwm_soc },
+	{ .compatible = "nvidia,tegra194-pwm", .data = &tegra194_pwm_soc },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, tegra_pwm_of_match);
+
+static const struct dev_pm_ops tegra_pwm_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(tegra_pwm_suspend, tegra_pwm_resume)
+};
+
+static struct platform_driver tegra_pwm_driver = {
+	.driver = {
+		.name = "tegra-pwm",
+		.of_match_table = tegra_pwm_of_match,
+		.pm = &tegra_pwm_pm_ops,
+	},
+	.probe = tegra_pwm_probe,
+	.remove = tegra_pwm_remove,
+};
+
+module_platform_driver(tegra_pwm_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Sandipan Patra <spatra@nvidia.com>");
+MODULE_DESCRIPTION("Tegra PWM controller driver");
+MODULE_ALIAS("platform:tegra-pwm");