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// SPDX-License-Identifier: GPL-2.0
/*
* STM32 Low-Power Timer PWM driver
*
* Copyright (C) STMicroelectronics 2017
*
* Author: Gerald Baeza <gerald.baeza@st.com>
*
* Inspired by Gerald Baeza's pwm-stm32 driver
*/
#include <linux/bitfield.h>
#include <linux/mfd/stm32-lptimer.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>
struct stm32_pwm_lp {
struct pwm_chip chip;
struct clk *clk;
struct regmap *regmap;
};
static inline struct stm32_pwm_lp *to_stm32_pwm_lp(struct pwm_chip *chip)
{
return container_of(chip, struct stm32_pwm_lp, chip);
}
/* STM32 Low-Power Timer is preceded by a configurable power-of-2 prescaler */
#define STM32_LPTIM_MAX_PRESCALER 128
static int stm32_pwm_lp_apply(struct pwm_chip *chip, struct pwm_device *pwm,
struct pwm_state *state)
{
struct stm32_pwm_lp *priv = to_stm32_pwm_lp(chip);
unsigned long long prd, div, dty;
struct pwm_state cstate;
u32 val, mask, cfgr, presc = 0;
bool reenable;
int ret;
pwm_get_state(pwm, &cstate);
reenable = !cstate.enabled;
if (!state->enabled) {
if (cstate.enabled) {
/* Disable LP timer */
ret = regmap_write(priv->regmap, STM32_LPTIM_CR, 0);
if (ret)
return ret;
/* disable clock to PWM counter */
clk_disable(priv->clk);
}
return 0;
}
/* Calculate the period and prescaler value */
div = (unsigned long long)clk_get_rate(priv->clk) * state->period;
do_div(div, NSEC_PER_SEC);
if (!div) {
/* Clock is too slow to achieve requested period. */
dev_dbg(priv->chip.dev, "Can't reach %u ns\n", state->period);
return -EINVAL;
}
prd = div;
while (div > STM32_LPTIM_MAX_ARR) {
presc++;
if ((1 << presc) > STM32_LPTIM_MAX_PRESCALER) {
dev_err(priv->chip.dev, "max prescaler exceeded\n");
return -EINVAL;
}
div = prd >> presc;
}
prd = div;
/* Calculate the duty cycle */
dty = prd * state->duty_cycle;
do_div(dty, state->period);
if (!cstate.enabled) {
/* enable clock to drive PWM counter */
ret = clk_enable(priv->clk);
if (ret)
return ret;
}
ret = regmap_read(priv->regmap, STM32_LPTIM_CFGR, &cfgr);
if (ret)
goto err;
if ((FIELD_GET(STM32_LPTIM_PRESC, cfgr) != presc) ||
(FIELD_GET(STM32_LPTIM_WAVPOL, cfgr) != state->polarity)) {
val = FIELD_PREP(STM32_LPTIM_PRESC, presc);
val |= FIELD_PREP(STM32_LPTIM_WAVPOL, state->polarity);
mask = STM32_LPTIM_PRESC | STM32_LPTIM_WAVPOL;
/* Must disable LP timer to modify CFGR */
reenable = true;
ret = regmap_write(priv->regmap, STM32_LPTIM_CR, 0);
if (ret)
goto err;
ret = regmap_update_bits(priv->regmap, STM32_LPTIM_CFGR, mask,
val);
if (ret)
goto err;
}
if (reenable) {
/* Must (re)enable LP timer to modify CMP & ARR */
ret = regmap_write(priv->regmap, STM32_LPTIM_CR,
STM32_LPTIM_ENABLE);
if (ret)
goto err;
}
ret = regmap_write(priv->regmap, STM32_LPTIM_ARR, prd - 1);
if (ret)
goto err;
ret = regmap_write(priv->regmap, STM32_LPTIM_CMP, prd - (1 + dty));
if (ret)
goto err;
/* ensure CMP & ARR registers are properly written */
ret = regmap_read_poll_timeout(priv->regmap, STM32_LPTIM_ISR, val,
(val & STM32_LPTIM_CMPOK_ARROK) == STM32_LPTIM_CMPOK_ARROK,
100, 1000);
if (ret) {
dev_err(priv->chip.dev, "ARR/CMP registers write issue\n");
goto err;
}
ret = regmap_write(priv->regmap, STM32_LPTIM_ICR,
STM32_LPTIM_CMPOKCF_ARROKCF);
if (ret)
goto err;
if (reenable) {
/* Start LP timer in continuous mode */
ret = regmap_update_bits(priv->regmap, STM32_LPTIM_CR,
STM32_LPTIM_CNTSTRT,
STM32_LPTIM_CNTSTRT);
if (ret) {
regmap_write(priv->regmap, STM32_LPTIM_CR, 0);
goto err;
}
}
return 0;
err:
if (!cstate.enabled)
clk_disable(priv->clk);
return ret;
}
static void stm32_pwm_lp_get_state(struct pwm_chip *chip,
struct pwm_device *pwm,
struct pwm_state *state)
{
struct stm32_pwm_lp *priv = to_stm32_pwm_lp(chip);
unsigned long rate = clk_get_rate(priv->clk);
u32 val, presc, prd;
u64 tmp;
regmap_read(priv->regmap, STM32_LPTIM_CR, &val);
state->enabled = !!FIELD_GET(STM32_LPTIM_ENABLE, val);
/* Keep PWM counter clock refcount in sync with PWM initial state */
if (state->enabled)
clk_enable(priv->clk);
regmap_read(priv->regmap, STM32_LPTIM_CFGR, &val);
presc = FIELD_GET(STM32_LPTIM_PRESC, val);
state->polarity = FIELD_GET(STM32_LPTIM_WAVPOL, val);
regmap_read(priv->regmap, STM32_LPTIM_ARR, &prd);
tmp = prd + 1;
tmp = (tmp << presc) * NSEC_PER_SEC;
state->period = DIV_ROUND_CLOSEST_ULL(tmp, rate);
regmap_read(priv->regmap, STM32_LPTIM_CMP, &val);
tmp = prd - val;
tmp = (tmp << presc) * NSEC_PER_SEC;
state->duty_cycle = DIV_ROUND_CLOSEST_ULL(tmp, rate);
}
static const struct pwm_ops stm32_pwm_lp_ops = {
.owner = THIS_MODULE,
.apply = stm32_pwm_lp_apply,
.get_state = stm32_pwm_lp_get_state,
};
static int stm32_pwm_lp_probe(struct platform_device *pdev)
{
struct stm32_lptimer *ddata = dev_get_drvdata(pdev->dev.parent);
struct stm32_pwm_lp *priv;
int ret;
priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
if (!priv)
return -ENOMEM;
priv->regmap = ddata->regmap;
priv->clk = ddata->clk;
priv->chip.base = -1;
priv->chip.dev = &pdev->dev;
priv->chip.ops = &stm32_pwm_lp_ops;
priv->chip.npwm = 1;
priv->chip.of_xlate = of_pwm_xlate_with_flags;
priv->chip.of_pwm_n_cells = 3;
ret = pwmchip_add(&priv->chip);
if (ret < 0)
return ret;
platform_set_drvdata(pdev, priv);
return 0;
}
static int stm32_pwm_lp_remove(struct platform_device *pdev)
{
struct stm32_pwm_lp *priv = platform_get_drvdata(pdev);
return pwmchip_remove(&priv->chip);
}
static const struct of_device_id stm32_pwm_lp_of_match[] = {
{ .compatible = "st,stm32-pwm-lp", },
{},
};
MODULE_DEVICE_TABLE(of, stm32_pwm_lp_of_match);
static struct platform_driver stm32_pwm_lp_driver = {
.probe = stm32_pwm_lp_probe,
.remove = stm32_pwm_lp_remove,
.driver = {
.name = "stm32-pwm-lp",
.of_match_table = of_match_ptr(stm32_pwm_lp_of_match),
},
};
module_platform_driver(stm32_pwm_lp_driver);
MODULE_ALIAS("platform:stm32-pwm-lp");
MODULE_DESCRIPTION("STMicroelectronics STM32 PWM LP driver");
MODULE_LICENSE("GPL v2");
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