--- /dev/null
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Toshiba Visconti pulse-width-modulation controller driver
+ *
+ * Copyright (c) 2020 - 2021 TOSHIBA CORPORATION
+ * Copyright (c) 2020 - 2021 Toshiba Electronic Devices & Storage Corporation
+ *
+ * Authors: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>
+ *
+ * Limitations:
+ * - The fixed input clock is running at 1 MHz and is divided by either 1,
+ * 2, 4 or 8.
+ * - When the settings of the PWM are modified, the new values are shadowed
+ * in hardware until the PIPGM_PCSR register is written and the currently
+ * running period is completed. This way the hardware switches atomically
+ * from the old setting to the new.
+ * - Disabling the hardware completes the currently running period and keeps
+ * the output at low level at all times.
+ */
+
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+
+#define PIPGM_PCSR(ch) (0x400 + 4 * (ch))
+#define PIPGM_PDUT(ch) (0x420 + 4 * (ch))
+#define PIPGM_PWMC(ch) (0x440 + 4 * (ch))
+
+#define PIPGM_PWMC_PWMACT BIT(5)
+#define PIPGM_PWMC_CLK_MASK GENMASK(1, 0)
+#define PIPGM_PWMC_POLARITY_MASK GENMASK(5, 5)
+
+struct visconti_pwm_chip {
+ struct pwm_chip chip;
+ void __iomem *base;
+};
+
+static inline struct visconti_pwm_chip *visconti_pwm_from_chip(struct pwm_chip *chip)
+{
+ return container_of(chip, struct visconti_pwm_chip, chip);
+}
+
+static int visconti_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+ const struct pwm_state *state)
+{
+ struct visconti_pwm_chip *priv = visconti_pwm_from_chip(chip);
+ u32 period, duty_cycle, pwmc0;
+
+ if (!state->enabled) {
+ writel(0, priv->base + PIPGM_PCSR(pwm->hwpwm));
+ return 0;
+ }
+
+ /*
+ * The biggest period the hardware can provide is
+ * (0xffff << 3) * 1000 ns
+ * This value fits easily in an u32, so simplify the maths by
+ * capping the values to 32 bit integers.
+ */
+ if (state->period > (0xffff << 3) * 1000)
+ period = (0xffff << 3) * 1000;
+ else
+ period = state->period;
+
+ if (state->duty_cycle > period)
+ duty_cycle = period;
+ else
+ duty_cycle = state->duty_cycle;
+
+ /*
+ * The input clock runs fixed at 1 MHz, so we have only
+ * microsecond resolution and so can divide by
+ * NSEC_PER_SEC / CLKFREQ = 1000 without losing precision.
+ */
+ period /= 1000;
+ duty_cycle /= 1000;
+
+ if (!period)
+ return -ERANGE;
+
+ /*
+ * PWMC controls a divider that divides the input clk by a
+ * power of two between 1 and 8. As a smaller divider yields
+ * higher precision, pick the smallest possible one.
+ */
+ if (period > 0xffff) {
+ pwmc0 = ilog2(period >> 16);
+ if (WARN_ON(pwmc0 > 3))
+ return -EINVAL;
+ } else {
+ pwmc0 = 0;
+ }
+
+ period >>= pwmc0;
+ duty_cycle >>= pwmc0;
+
+ if (state->polarity == PWM_POLARITY_INVERSED)
+ pwmc0 |= PIPGM_PWMC_PWMACT;
+ writel(pwmc0, priv->base + PIPGM_PWMC(pwm->hwpwm));
+ writel(duty_cycle, priv->base + PIPGM_PDUT(pwm->hwpwm));
+ writel(period, priv->base + PIPGM_PCSR(pwm->hwpwm));
+
+ return 0;
+}
+
+static void visconti_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+ struct pwm_state *state)
+{
+ struct visconti_pwm_chip *priv = visconti_pwm_from_chip(chip);
+ u32 period, duty, pwmc0, pwmc0_clk;
+
+ period = readl(priv->base + PIPGM_PCSR(pwm->hwpwm));
+ duty = readl(priv->base + PIPGM_PDUT(pwm->hwpwm));
+ pwmc0 = readl(priv->base + PIPGM_PWMC(pwm->hwpwm));
+ pwmc0_clk = pwmc0 & PIPGM_PWMC_CLK_MASK;
+
+ state->period = (period << pwmc0_clk) * NSEC_PER_USEC;
+ state->duty_cycle = (duty << pwmc0_clk) * NSEC_PER_USEC;
+ if (pwmc0 & PIPGM_PWMC_POLARITY_MASK)
+ state->polarity = PWM_POLARITY_INVERSED;
+ else
+ state->polarity = PWM_POLARITY_NORMAL;
+
+ state->enabled = true;
+}
+
+static const struct pwm_ops visconti_pwm_ops = {
+ .apply = visconti_pwm_apply,
+ .get_state = visconti_pwm_get_state,
+ .owner = THIS_MODULE,
+};
+
+static int visconti_pwm_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct visconti_pwm_chip *priv;
+ int ret;
+
+ priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+ if (!priv)
+ return -ENOMEM;
+
+ priv->base = devm_platform_ioremap_resource(pdev, 0);
+ if (IS_ERR(priv->base))
+ return PTR_ERR(priv->base);
+
+ platform_set_drvdata(pdev, priv);
+
+ priv->chip.dev = dev;
+ priv->chip.ops = &visconti_pwm_ops;
+ priv->chip.npwm = 4;
+
+ ret = pwmchip_add(&priv->chip);
+ if (ret < 0)
+ return dev_err_probe(&pdev->dev, ret, "Cannot register visconti PWM\n");
+
+ return 0;
+}
+
+static int visconti_pwm_remove(struct platform_device *pdev)
+{
+ struct visconti_pwm_chip *priv = platform_get_drvdata(pdev);
+
+ pwmchip_remove(&priv->chip);
+
+ return 0;
+}
+
+static const struct of_device_id visconti_pwm_of_match[] = {
+ { .compatible = "toshiba,visconti-pwm", },
+ { }
+};
+MODULE_DEVICE_TABLE(of, visconti_pwm_of_match);
+
+static struct platform_driver visconti_pwm_driver = {
+ .driver = {
+ .name = "pwm-visconti",
+ .of_match_table = visconti_pwm_of_match,
+ },
+ .probe = visconti_pwm_probe,
+ .remove = visconti_pwm_remove,
+};
+module_platform_driver(visconti_pwm_driver);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>");
+MODULE_ALIAS("platform:pwm-visconti");
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