linuxdebug/drivers/pwm/pwm-sifive.c

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2024-07-16 15:50:57 +02:00
// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2017-2018 SiFive
* For SiFive's PWM IP block documentation please refer Chapter 14 of
* Reference Manual : https://static.dev.sifive.com/FU540-C000-v1.0.pdf
*
* Limitations:
* - When changing both duty cycle and period, we cannot prevent in
* software that the output might produce a period with mixed
* settings (new period length and old duty cycle).
* - The hardware cannot generate a 100% duty cycle.
* - The hardware generates only inverted output.
*/
#include <linux/clk.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>
#include <linux/slab.h>
#include <linux/bitfield.h>
/* Register offsets */
#define PWM_SIFIVE_PWMCFG 0x0
#define PWM_SIFIVE_PWMCOUNT 0x8
#define PWM_SIFIVE_PWMS 0x10
#define PWM_SIFIVE_PWMCMP(i) (0x20 + 4 * (i))
/* PWMCFG fields */
#define PWM_SIFIVE_PWMCFG_SCALE GENMASK(3, 0)
#define PWM_SIFIVE_PWMCFG_STICKY BIT(8)
#define PWM_SIFIVE_PWMCFG_ZERO_CMP BIT(9)
#define PWM_SIFIVE_PWMCFG_DEGLITCH BIT(10)
#define PWM_SIFIVE_PWMCFG_EN_ALWAYS BIT(12)
#define PWM_SIFIVE_PWMCFG_EN_ONCE BIT(13)
#define PWM_SIFIVE_PWMCFG_CENTER BIT(16)
#define PWM_SIFIVE_PWMCFG_GANG BIT(24)
#define PWM_SIFIVE_PWMCFG_IP BIT(28)
#define PWM_SIFIVE_CMPWIDTH 16
#define PWM_SIFIVE_DEFAULT_PERIOD 10000000
struct pwm_sifive_ddata {
struct pwm_chip chip;
struct mutex lock; /* lock to protect user_count and approx_period */
struct notifier_block notifier;
struct clk *clk;
void __iomem *regs;
unsigned int real_period;
unsigned int approx_period;
int user_count;
};
static inline
struct pwm_sifive_ddata *pwm_sifive_chip_to_ddata(struct pwm_chip *c)
{
return container_of(c, struct pwm_sifive_ddata, chip);
}
static int pwm_sifive_request(struct pwm_chip *chip, struct pwm_device *pwm)
{
struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
mutex_lock(&ddata->lock);
ddata->user_count++;
mutex_unlock(&ddata->lock);
return 0;
}
static void pwm_sifive_free(struct pwm_chip *chip, struct pwm_device *pwm)
{
struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
mutex_lock(&ddata->lock);
ddata->user_count--;
mutex_unlock(&ddata->lock);
}
/* Called holding ddata->lock */
static void pwm_sifive_update_clock(struct pwm_sifive_ddata *ddata,
unsigned long rate)
{
unsigned long long num;
unsigned long scale_pow;
int scale;
u32 val;
/*
* The PWM unit is used with pwmzerocmp=0, so the only way to modify the
* period length is using pwmscale which provides the number of bits the
* counter is shifted before being feed to the comparators. A period
* lasts (1 << (PWM_SIFIVE_CMPWIDTH + pwmscale)) clock ticks.
* (1 << (PWM_SIFIVE_CMPWIDTH + scale)) * 10^9/rate = period
*/
scale_pow = div64_ul(ddata->approx_period * (u64)rate, NSEC_PER_SEC);
scale = clamp(ilog2(scale_pow) - PWM_SIFIVE_CMPWIDTH, 0, 0xf);
val = PWM_SIFIVE_PWMCFG_EN_ALWAYS |
FIELD_PREP(PWM_SIFIVE_PWMCFG_SCALE, scale);
writel(val, ddata->regs + PWM_SIFIVE_PWMCFG);
/* As scale <= 15 the shift operation cannot overflow. */
num = (unsigned long long)NSEC_PER_SEC << (PWM_SIFIVE_CMPWIDTH + scale);
ddata->real_period = div64_ul(num, rate);
dev_dbg(ddata->chip.dev,
"New real_period = %u ns\n", ddata->real_period);
}
static int pwm_sifive_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
struct pwm_state *state)
{
struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
u32 duty, val;
duty = readl(ddata->regs + PWM_SIFIVE_PWMCMP(pwm->hwpwm));
state->enabled = duty > 0;
val = readl(ddata->regs + PWM_SIFIVE_PWMCFG);
if (!(val & PWM_SIFIVE_PWMCFG_EN_ALWAYS))
state->enabled = false;
state->period = ddata->real_period;
state->duty_cycle =
(u64)duty * ddata->real_period >> PWM_SIFIVE_CMPWIDTH;
state->polarity = PWM_POLARITY_INVERSED;
return 0;
}
static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm,
const struct pwm_state *state)
{
struct pwm_sifive_ddata *ddata = pwm_sifive_chip_to_ddata(chip);
struct pwm_state cur_state;
unsigned int duty_cycle;
unsigned long long num;
bool enabled;
int ret = 0;
u32 frac;
if (state->polarity != PWM_POLARITY_INVERSED)
return -EINVAL;
cur_state = pwm->state;
enabled = cur_state.enabled;
duty_cycle = state->duty_cycle;
if (!state->enabled)
duty_cycle = 0;
/*
* The problem of output producing mixed setting as mentioned at top,
* occurs here. To minimize the window for this problem, we are
* calculating the register values first and then writing them
* consecutively
*/
num = (u64)duty_cycle * (1U << PWM_SIFIVE_CMPWIDTH);
frac = DIV64_U64_ROUND_CLOSEST(num, state->period);
/* The hardware cannot generate a 100% duty cycle */
frac = min(frac, (1U << PWM_SIFIVE_CMPWIDTH) - 1);
mutex_lock(&ddata->lock);
if (state->period != ddata->approx_period) {
/*
* Don't let a 2nd user change the period underneath the 1st user.
* However if ddate->approx_period == 0 this is the first time we set
* any period, so let whoever gets here first set the period so other
* users who agree on the period won't fail.
*/
if (ddata->user_count != 1 && ddata->approx_period) {
mutex_unlock(&ddata->lock);
return -EBUSY;
}
ddata->approx_period = state->period;
pwm_sifive_update_clock(ddata, clk_get_rate(ddata->clk));
}
mutex_unlock(&ddata->lock);
/*
* If the PWM is enabled the clk is already on. So only enable it
* conditionally to have it on exactly once afterwards independent of
* the PWM state.
*/
if (!enabled) {
ret = clk_enable(ddata->clk);
if (ret) {
dev_err(ddata->chip.dev, "Enable clk failed\n");
return ret;
}
}
writel(frac, ddata->regs + PWM_SIFIVE_PWMCMP(pwm->hwpwm));
if (!state->enabled)
clk_disable(ddata->clk);
return 0;
}
static const struct pwm_ops pwm_sifive_ops = {
.request = pwm_sifive_request,
.free = pwm_sifive_free,
.get_state = pwm_sifive_get_state,
.apply = pwm_sifive_apply,
.owner = THIS_MODULE,
};
static int pwm_sifive_clock_notifier(struct notifier_block *nb,
unsigned long event, void *data)
{
struct clk_notifier_data *ndata = data;
struct pwm_sifive_ddata *ddata =
container_of(nb, struct pwm_sifive_ddata, notifier);
if (event == POST_RATE_CHANGE) {
mutex_lock(&ddata->lock);
pwm_sifive_update_clock(ddata, ndata->new_rate);
mutex_unlock(&ddata->lock);
}
return NOTIFY_OK;
}
static int pwm_sifive_probe(struct platform_device *pdev)
{
struct device *dev = &pdev->dev;
struct pwm_sifive_ddata *ddata;
struct pwm_chip *chip;
int ret;
u32 val;
unsigned int enabled_pwms = 0, enabled_clks = 1;
ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL);
if (!ddata)
return -ENOMEM;
mutex_init(&ddata->lock);
chip = &ddata->chip;
chip->dev = dev;
chip->ops = &pwm_sifive_ops;
chip->npwm = 4;
ddata->regs = devm_platform_ioremap_resource(pdev, 0);
if (IS_ERR(ddata->regs))
return PTR_ERR(ddata->regs);
ddata->clk = devm_clk_get(dev, NULL);
if (IS_ERR(ddata->clk))
return dev_err_probe(dev, PTR_ERR(ddata->clk),
"Unable to find controller clock\n");
ret = clk_prepare_enable(ddata->clk);
if (ret) {
dev_err(dev, "failed to enable clock for pwm: %d\n", ret);
return ret;
}
val = readl(ddata->regs + PWM_SIFIVE_PWMCFG);
if (val & PWM_SIFIVE_PWMCFG_EN_ALWAYS) {
unsigned int i;
for (i = 0; i < chip->npwm; ++i) {
val = readl(ddata->regs + PWM_SIFIVE_PWMCMP(i));
if (val > 0)
++enabled_pwms;
}
}
/* The clk should be on once for each running PWM. */
if (enabled_pwms) {
while (enabled_clks < enabled_pwms) {
/* This is not expected to fail as the clk is already on */
ret = clk_enable(ddata->clk);
if (unlikely(ret)) {
dev_err_probe(dev, ret, "Failed to enable clk\n");
goto disable_clk;
}
++enabled_clks;
}
} else {
clk_disable(ddata->clk);
enabled_clks = 0;
}
/* Watch for changes to underlying clock frequency */
ddata->notifier.notifier_call = pwm_sifive_clock_notifier;
ret = clk_notifier_register(ddata->clk, &ddata->notifier);
if (ret) {
dev_err(dev, "failed to register clock notifier: %d\n", ret);
goto disable_clk;
}
ret = pwmchip_add(chip);
if (ret < 0) {
dev_err(dev, "cannot register PWM: %d\n", ret);
goto unregister_clk;
}
platform_set_drvdata(pdev, ddata);
dev_dbg(dev, "SiFive PWM chip registered %d PWMs\n", chip->npwm);
return 0;
unregister_clk:
clk_notifier_unregister(ddata->clk, &ddata->notifier);
disable_clk:
while (enabled_clks) {
clk_disable(ddata->clk);
--enabled_clks;
}
clk_unprepare(ddata->clk);
return ret;
}
static int pwm_sifive_remove(struct platform_device *dev)
{
struct pwm_sifive_ddata *ddata = platform_get_drvdata(dev);
struct pwm_device *pwm;
int ch;
pwmchip_remove(&ddata->chip);
clk_notifier_unregister(ddata->clk, &ddata->notifier);
for (ch = 0; ch < ddata->chip.npwm; ch++) {
pwm = &ddata->chip.pwms[ch];
if (pwm->state.enabled)
clk_disable(ddata->clk);
}
clk_unprepare(ddata->clk);
return 0;
}
static const struct of_device_id pwm_sifive_of_match[] = {
{ .compatible = "sifive,pwm0" },
{},
};
MODULE_DEVICE_TABLE(of, pwm_sifive_of_match);
static struct platform_driver pwm_sifive_driver = {
.probe = pwm_sifive_probe,
.remove = pwm_sifive_remove,
.driver = {
.name = "pwm-sifive",
.of_match_table = pwm_sifive_of_match,
},
};
module_platform_driver(pwm_sifive_driver);
MODULE_DESCRIPTION("SiFive PWM driver");
MODULE_LICENSE("GPL v2");