// 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 <[email protected]>
*
* 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 {
void __iomem *base;
};
static inline struct visconti_pwm_chip *visconti_pwm_from_chip(struct pwm_chip *chip)
{
return pwmchip_get_drvdata(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,
};
static int visconti_pwm_probe(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
struct pwm_chip *chip;
struct visconti_pwm_chip *priv;
int ret;
chip = devm_pwmchip_alloc(dev, 4, sizeof(*priv));
if (IS_ERR(chip))
return PTR_ERR(chip);
priv = visconti_pwm_from_chip(chip);
priv->base = devm_platform_ioremap_resource(pdev, 0);
if (IS_ERR(priv->base))
return PTR_ERR(priv->base);
chip->ops = &visconti_pwm_ops;
ret = devm_pwmchip_add(&pdev->dev, 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_DESCRIPTION("Toshiba Visconti Pulse Width Modulator driver");
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Nobuhiro Iwamatsu <[email protected]>");
MODULE_ALIAS("platform:pwm-visconti");
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