diff options
Diffstat (limited to 'drivers/pwm/pwm-visconti.c')
| -rw-r--r-- | drivers/pwm/pwm-visconti.c | 177 |
1 files changed, 177 insertions, 0 deletions
diff --git a/drivers/pwm/pwm-visconti.c b/drivers/pwm/pwm-visconti.c new file mode 100644 index 0000000000..7f7591a238 --- /dev/null +++ b/drivers/pwm/pwm-visconti.c @@ -0,0 +1,177 @@ +// 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.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. As period is at most 0xffff << 3, pwmc0 is + * in the intended range [0..3]. + */ + pwmc0 = fls(period >> 16); + if (WARN_ON(pwmc0 > 3)) + return -EINVAL; + + 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 int 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; + + return 0; +} + +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); + + priv->chip.dev = dev; + priv->chip.ops = &visconti_pwm_ops; + priv->chip.npwm = 4; + + ret = devm_pwmchip_add(&pdev->dev, &priv->chip); + if (ret < 0) + return dev_err_probe(&pdev->dev, ret, "Cannot register visconti PWM\n"); + + 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, +}; +module_platform_driver(visconti_pwm_driver); + +MODULE_LICENSE("GPL v2"); +MODULE_AUTHOR("Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>"); +MODULE_ALIAS("platform:pwm-visconti"); |