linuxdebug/drivers/pwm/pwm-tegra.c

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2024-07-16 15:50:57 +02:00
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* drivers/pwm/pwm-tegra.c
*
* Tegra pulse-width-modulation controller driver
*
* Copyright (c) 2010-2020, NVIDIA Corporation.
* Based on arch/arm/plat-mxc/pwm.c by Sascha Hauer <s.hauer@pengutronix.de>
*
* Overview of Tegra Pulse Width Modulator Register:
* 1. 13-bit: Frequency division (SCALE)
* 2. 8-bit : Pulse division (DUTY)
* 3. 1-bit : Enable bit
*
* The PWM clock frequency is divided by 256 before subdividing it based
* on the programmable frequency division value to generate the required
* frequency for PWM output. The maximum output frequency that can be
* achieved is (max rate of source clock) / 256.
* e.g. if source clock rate is 408 MHz, maximum output frequency can be:
* 408 MHz/256 = 1.6 MHz.
* This 1.6 MHz frequency can further be divided using SCALE value in PWM.
*
* PWM pulse width: 8 bits are usable [23:16] for varying pulse width.
* To achieve 100% duty cycle, program Bit [24] of this register to
* 1b1. In which case the other bits [23:16] are set to don't care.
*
* Limitations:
* - When PWM is disabled, the output is driven to inactive.
* - It does not allow the current PWM period to complete and
* stops abruptly.
*
* - If the register is reconfigured while PWM is running,
* it does not complete the currently running period.
*
* - If the user input duty is beyond acceptible limits,
* -EINVAL is returned.
*/
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/pm_opp.h>
#include <linux/pwm.h>
#include <linux/platform_device.h>
#include <linux/pinctrl/consumer.h>
#include <linux/pm_runtime.h>
#include <linux/slab.h>
#include <linux/reset.h>
#include <soc/tegra/common.h>
#define PWM_ENABLE (1 << 31)
#define PWM_DUTY_WIDTH 8
#define PWM_DUTY_SHIFT 16
#define PWM_SCALE_WIDTH 13
#define PWM_SCALE_SHIFT 0
struct tegra_pwm_soc {
unsigned int num_channels;
/* Maximum IP frequency for given SoCs */
unsigned long max_frequency;
};
struct tegra_pwm_chip {
struct pwm_chip chip;
struct device *dev;
struct clk *clk;
struct reset_control*rst;
unsigned long clk_rate;
unsigned long min_period_ns;
void __iomem *regs;
const struct tegra_pwm_soc *soc;
};
static inline struct tegra_pwm_chip *to_tegra_pwm_chip(struct pwm_chip *chip)
{
return container_of(chip, struct tegra_pwm_chip, chip);
}
static inline u32 pwm_readl(struct tegra_pwm_chip *pc, unsigned int offset)
{
return readl(pc->regs + (offset << 4));
}
static inline void pwm_writel(struct tegra_pwm_chip *pc, unsigned int offset, u32 value)
{
writel(value, pc->regs + (offset << 4));
}
static int tegra_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
int duty_ns, int period_ns)
{
struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
unsigned long long c = duty_ns;
unsigned long rate, required_clk_rate;
u32 val = 0;
int err;
/*
* Convert from duty_ns / period_ns to a fixed number of duty ticks
* per (1 << PWM_DUTY_WIDTH) cycles and make sure to round to the
* nearest integer during division.
*/
c *= (1 << PWM_DUTY_WIDTH);
c = DIV_ROUND_CLOSEST_ULL(c, period_ns);
val = (u32)c << PWM_DUTY_SHIFT;
/*
* min period = max clock limit >> PWM_DUTY_WIDTH
*/
if (period_ns < pc->min_period_ns)
return -EINVAL;
/*
* Compute the prescaler value for which (1 << PWM_DUTY_WIDTH)
* cycles at the PWM clock rate will take period_ns nanoseconds.
*
* num_channels: If single instance of PWM controller has multiple
* channels (e.g. Tegra210 or older) then it is not possible to
* configure separate clock rates to each of the channels, in such
* case the value stored during probe will be referred.
*
* If every PWM controller instance has one channel respectively, i.e.
* nums_channels == 1 then only the clock rate can be modified
* dynamically (e.g. Tegra186 or Tegra194).
*/
if (pc->soc->num_channels == 1) {
/*
* Rate is multiplied with 2^PWM_DUTY_WIDTH so that it matches
* with the maximum possible rate that the controller can
* provide. Any further lower value can be derived by setting
* PFM bits[0:12].
*
* required_clk_rate is a reference rate for source clock and
* it is derived based on user requested period. By setting the
* source clock rate as required_clk_rate, PWM controller will
* be able to configure the requested period.
*/
required_clk_rate = DIV_ROUND_UP_ULL((u64)NSEC_PER_SEC << PWM_DUTY_WIDTH,
period_ns);
if (required_clk_rate > clk_round_rate(pc->clk, required_clk_rate))
/*
* required_clk_rate is a lower bound for the input
* rate; for lower rates there is no value for PWM_SCALE
* that yields a period less than or equal to the
* requested period. Hence, for lower rates, double the
* required_clk_rate to get a clock rate that can meet
* the requested period.
*/
required_clk_rate *= 2;
err = dev_pm_opp_set_rate(pc->dev, required_clk_rate);
if (err < 0)
return -EINVAL;
/* Store the new rate for further references */
pc->clk_rate = clk_get_rate(pc->clk);
}
/* Consider precision in PWM_SCALE_WIDTH rate calculation */
rate = mul_u64_u64_div_u64(pc->clk_rate, period_ns,
(u64)NSEC_PER_SEC << PWM_DUTY_WIDTH);
/*
* Since the actual PWM divider is the register's frequency divider
* field plus 1, we need to decrement to get the correct value to
* write to the register.
*/
if (rate > 0)
rate--;
else
return -EINVAL;
/*
* Make sure that the rate will fit in the register's frequency
* divider field.
*/
if (rate >> PWM_SCALE_WIDTH)
return -EINVAL;
val |= rate << PWM_SCALE_SHIFT;
/*
* If the PWM channel is disabled, make sure to turn on the clock
* before writing the register. Otherwise, keep it enabled.
*/
if (!pwm_is_enabled(pwm)) {
err = pm_runtime_resume_and_get(pc->dev);
if (err)
return err;
} else
val |= PWM_ENABLE;
pwm_writel(pc, pwm->hwpwm, val);
/*
* If the PWM is not enabled, turn the clock off again to save power.
*/
if (!pwm_is_enabled(pwm))
pm_runtime_put(pc->dev);
return 0;
}
static int tegra_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
int rc = 0;
u32 val;
rc = pm_runtime_resume_and_get(pc->dev);
if (rc)
return rc;
val = pwm_readl(pc, pwm->hwpwm);
val |= PWM_ENABLE;
pwm_writel(pc, pwm->hwpwm, val);
return 0;
}
static void tegra_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
{
struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
u32 val;
val = pwm_readl(pc, pwm->hwpwm);
val &= ~PWM_ENABLE;
pwm_writel(pc, pwm->hwpwm, val);
pm_runtime_put_sync(pc->dev);
}
static int tegra_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
const struct pwm_state *state)
{
int err;
bool enabled = pwm->state.enabled;
if (state->polarity != PWM_POLARITY_NORMAL)
return -EINVAL;
if (!state->enabled) {
if (enabled)
tegra_pwm_disable(chip, pwm);
return 0;
}
err = tegra_pwm_config(pwm->chip, pwm, state->duty_cycle, state->period);
if (err)
return err;
if (!enabled)
err = tegra_pwm_enable(chip, pwm);
return err;
}
static const struct pwm_ops tegra_pwm_ops = {
.apply = tegra_pwm_apply,
.owner = THIS_MODULE,
};
static int tegra_pwm_probe(struct platform_device *pdev)
{
struct tegra_pwm_chip *pc;
int ret;
pc = devm_kzalloc(&pdev->dev, sizeof(*pc), GFP_KERNEL);
if (!pc)
return -ENOMEM;
pc->soc = of_device_get_match_data(&pdev->dev);
pc->dev = &pdev->dev;
pc->regs = devm_platform_ioremap_resource(pdev, 0);
if (IS_ERR(pc->regs))
return PTR_ERR(pc->regs);
platform_set_drvdata(pdev, pc);
pc->clk = devm_clk_get(&pdev->dev, NULL);
if (IS_ERR(pc->clk))
return PTR_ERR(pc->clk);
ret = devm_tegra_core_dev_init_opp_table_common(&pdev->dev);
if (ret)
return ret;
pm_runtime_enable(&pdev->dev);
ret = pm_runtime_resume_and_get(&pdev->dev);
if (ret)
return ret;
/* Set maximum frequency of the IP */
ret = dev_pm_opp_set_rate(pc->dev, pc->soc->max_frequency);
if (ret < 0) {
dev_err(&pdev->dev, "Failed to set max frequency: %d\n", ret);
goto put_pm;
}
/*
* The requested and configured frequency may differ due to
* clock register resolutions. Get the configured frequency
* so that PWM period can be calculated more accurately.
*/
pc->clk_rate = clk_get_rate(pc->clk);
/* Set minimum limit of PWM period for the IP */
pc->min_period_ns =
(NSEC_PER_SEC / (pc->soc->max_frequency >> PWM_DUTY_WIDTH)) + 1;
pc->rst = devm_reset_control_get_exclusive(&pdev->dev, "pwm");
if (IS_ERR(pc->rst)) {
ret = PTR_ERR(pc->rst);
dev_err(&pdev->dev, "Reset control is not found: %d\n", ret);
goto put_pm;
}
reset_control_deassert(pc->rst);
pc->chip.dev = &pdev->dev;
pc->chip.ops = &tegra_pwm_ops;
pc->chip.npwm = pc->soc->num_channels;
ret = pwmchip_add(&pc->chip);
if (ret < 0) {
dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
reset_control_assert(pc->rst);
goto put_pm;
}
pm_runtime_put(&pdev->dev);
return 0;
put_pm:
pm_runtime_put_sync_suspend(&pdev->dev);
pm_runtime_force_suspend(&pdev->dev);
return ret;
}
static int tegra_pwm_remove(struct platform_device *pdev)
{
struct tegra_pwm_chip *pc = platform_get_drvdata(pdev);
pwmchip_remove(&pc->chip);
reset_control_assert(pc->rst);
pm_runtime_force_suspend(&pdev->dev);
return 0;
}
static int __maybe_unused tegra_pwm_runtime_suspend(struct device *dev)
{
struct tegra_pwm_chip *pc = dev_get_drvdata(dev);
int err;
clk_disable_unprepare(pc->clk);
err = pinctrl_pm_select_sleep_state(dev);
if (err) {
clk_prepare_enable(pc->clk);
return err;
}
return 0;
}
static int __maybe_unused tegra_pwm_runtime_resume(struct device *dev)
{
struct tegra_pwm_chip *pc = dev_get_drvdata(dev);
int err;
err = pinctrl_pm_select_default_state(dev);
if (err)
return err;
err = clk_prepare_enable(pc->clk);
if (err) {
pinctrl_pm_select_sleep_state(dev);
return err;
}
return 0;
}
static const struct tegra_pwm_soc tegra20_pwm_soc = {
.num_channels = 4,
.max_frequency = 48000000UL,
};
static const struct tegra_pwm_soc tegra186_pwm_soc = {
.num_channels = 1,
.max_frequency = 102000000UL,
};
static const struct tegra_pwm_soc tegra194_pwm_soc = {
.num_channels = 1,
.max_frequency = 408000000UL,
};
static const struct of_device_id tegra_pwm_of_match[] = {
{ .compatible = "nvidia,tegra20-pwm", .data = &tegra20_pwm_soc },
{ .compatible = "nvidia,tegra186-pwm", .data = &tegra186_pwm_soc },
{ .compatible = "nvidia,tegra194-pwm", .data = &tegra194_pwm_soc },
{ }
};
MODULE_DEVICE_TABLE(of, tegra_pwm_of_match);
static const struct dev_pm_ops tegra_pwm_pm_ops = {
SET_RUNTIME_PM_OPS(tegra_pwm_runtime_suspend, tegra_pwm_runtime_resume,
NULL)
SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
pm_runtime_force_resume)
};
static struct platform_driver tegra_pwm_driver = {
.driver = {
.name = "tegra-pwm",
.of_match_table = tegra_pwm_of_match,
.pm = &tegra_pwm_pm_ops,
},
.probe = tegra_pwm_probe,
.remove = tegra_pwm_remove,
};
module_platform_driver(tegra_pwm_driver);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Sandipan Patra <spatra@nvidia.com>");
MODULE_DESCRIPTION("Tegra PWM controller driver");
MODULE_ALIAS("platform:tegra-pwm");