linux/drivers/pwm/pwm-atmel.c
Colin Ian King dc1adb3ce4 pwm: atmel: Remove redundant initialization of variable timeout
The variable timeout is being initialized with a value that is never
read, it is being re-assigned the same value later on. Remove the
redundant initialization and keep the latter assignment because it's
closer to the use of the variable.

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
2022-02-24 13:54:05 +01:00

537 lines
13 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* Driver for Atmel Pulse Width Modulation Controller
*
* Copyright (C) 2013 Atmel Corporation
* Bo Shen <voice.shen@atmel.com>
*
* Links to reference manuals for the supported PWM chips can be found in
* Documentation/arm/microchip.rst.
*
* Limitations:
* - Periods start with the inactive level.
* - Hardware has to be stopped in general to update settings.
*
* Software bugs/possible improvements:
* - When atmel_pwm_apply() is called with state->enabled=false a change in
* state->polarity isn't honored.
* - Instead of sleeping to wait for a completed period, the interrupt
* functionality could be used.
*/
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>
#include <linux/slab.h>
/* The following is global registers for PWM controller */
#define PWM_ENA 0x04
#define PWM_DIS 0x08
#define PWM_SR 0x0C
#define PWM_ISR 0x1C
/* Bit field in SR */
#define PWM_SR_ALL_CH_ON 0x0F
/* The following register is PWM channel related registers */
#define PWM_CH_REG_OFFSET 0x200
#define PWM_CH_REG_SIZE 0x20
#define PWM_CMR 0x0
/* Bit field in CMR */
#define PWM_CMR_CPOL (1 << 9)
#define PWM_CMR_UPD_CDTY (1 << 10)
#define PWM_CMR_CPRE_MSK 0xF
/* The following registers for PWM v1 */
#define PWMV1_CDTY 0x04
#define PWMV1_CPRD 0x08
#define PWMV1_CUPD 0x10
/* The following registers for PWM v2 */
#define PWMV2_CDTY 0x04
#define PWMV2_CDTYUPD 0x08
#define PWMV2_CPRD 0x0C
#define PWMV2_CPRDUPD 0x10
#define PWM_MAX_PRES 10
struct atmel_pwm_registers {
u8 period;
u8 period_upd;
u8 duty;
u8 duty_upd;
};
struct atmel_pwm_config {
u32 period_bits;
};
struct atmel_pwm_data {
struct atmel_pwm_registers regs;
struct atmel_pwm_config cfg;
};
struct atmel_pwm_chip {
struct pwm_chip chip;
struct clk *clk;
void __iomem *base;
const struct atmel_pwm_data *data;
/*
* The hardware supports a mechanism to update a channel's duty cycle at
* the end of the currently running period. When such an update is
* pending we delay disabling the PWM until the new configuration is
* active because otherwise pmw_config(duty_cycle=0); pwm_disable();
* might not result in an inactive output.
* This bitmask tracks for which channels an update is pending in
* hardware.
*/
u32 update_pending;
/* Protects .update_pending */
spinlock_t lock;
};
static inline struct atmel_pwm_chip *to_atmel_pwm_chip(struct pwm_chip *chip)
{
return container_of(chip, struct atmel_pwm_chip, chip);
}
static inline u32 atmel_pwm_readl(struct atmel_pwm_chip *chip,
unsigned long offset)
{
return readl_relaxed(chip->base + offset);
}
static inline void atmel_pwm_writel(struct atmel_pwm_chip *chip,
unsigned long offset, unsigned long val)
{
writel_relaxed(val, chip->base + offset);
}
static inline u32 atmel_pwm_ch_readl(struct atmel_pwm_chip *chip,
unsigned int ch, unsigned long offset)
{
unsigned long base = PWM_CH_REG_OFFSET + ch * PWM_CH_REG_SIZE;
return atmel_pwm_readl(chip, base + offset);
}
static inline void atmel_pwm_ch_writel(struct atmel_pwm_chip *chip,
unsigned int ch, unsigned long offset,
unsigned long val)
{
unsigned long base = PWM_CH_REG_OFFSET + ch * PWM_CH_REG_SIZE;
atmel_pwm_writel(chip, base + offset, val);
}
static void atmel_pwm_update_pending(struct atmel_pwm_chip *chip)
{
/*
* Each channel that has its bit in ISR set started a new period since
* ISR was cleared and so there is no more update pending. Note that
* reading ISR clears it, so this needs to handle all channels to not
* loose information.
*/
u32 isr = atmel_pwm_readl(chip, PWM_ISR);
chip->update_pending &= ~isr;
}
static void atmel_pwm_set_pending(struct atmel_pwm_chip *chip, unsigned int ch)
{
spin_lock(&chip->lock);
/*
* Clear pending flags in hardware because otherwise there might still
* be a stale flag in ISR.
*/
atmel_pwm_update_pending(chip);
chip->update_pending |= (1 << ch);
spin_unlock(&chip->lock);
}
static int atmel_pwm_test_pending(struct atmel_pwm_chip *chip, unsigned int ch)
{
int ret = 0;
spin_lock(&chip->lock);
if (chip->update_pending & (1 << ch)) {
atmel_pwm_update_pending(chip);
if (chip->update_pending & (1 << ch))
ret = 1;
}
spin_unlock(&chip->lock);
return ret;
}
static int atmel_pwm_wait_nonpending(struct atmel_pwm_chip *chip, unsigned int ch)
{
unsigned long timeout = jiffies + 2 * HZ;
int ret;
while ((ret = atmel_pwm_test_pending(chip, ch)) &&
time_before(jiffies, timeout))
usleep_range(10, 100);
return ret ? -ETIMEDOUT : 0;
}
static int atmel_pwm_calculate_cprd_and_pres(struct pwm_chip *chip,
unsigned long clkrate,
const struct pwm_state *state,
unsigned long *cprd, u32 *pres)
{
struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
unsigned long long cycles = state->period;
int shift;
/* Calculate the period cycles and prescale value */
cycles *= clkrate;
do_div(cycles, NSEC_PER_SEC);
/*
* The register for the period length is cfg.period_bits bits wide.
* So for each bit the number of clock cycles is wider divide the input
* clock frequency by two using pres and shift cprd accordingly.
*/
shift = fls(cycles) - atmel_pwm->data->cfg.period_bits;
if (shift > PWM_MAX_PRES) {
dev_err(chip->dev, "pres exceeds the maximum value\n");
return -EINVAL;
} else if (shift > 0) {
*pres = shift;
cycles >>= *pres;
} else {
*pres = 0;
}
*cprd = cycles;
return 0;
}
static void atmel_pwm_calculate_cdty(const struct pwm_state *state,
unsigned long clkrate, unsigned long cprd,
u32 pres, unsigned long *cdty)
{
unsigned long long cycles = state->duty_cycle;
cycles *= clkrate;
do_div(cycles, NSEC_PER_SEC);
cycles >>= pres;
*cdty = cprd - cycles;
}
static void atmel_pwm_update_cdty(struct pwm_chip *chip, struct pwm_device *pwm,
unsigned long cdty)
{
struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
u32 val;
if (atmel_pwm->data->regs.duty_upd ==
atmel_pwm->data->regs.period_upd) {
val = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm, PWM_CMR);
val &= ~PWM_CMR_UPD_CDTY;
atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWM_CMR, val);
}
atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm,
atmel_pwm->data->regs.duty_upd, cdty);
atmel_pwm_set_pending(atmel_pwm, pwm->hwpwm);
}
static void atmel_pwm_set_cprd_cdty(struct pwm_chip *chip,
struct pwm_device *pwm,
unsigned long cprd, unsigned long cdty)
{
struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm,
atmel_pwm->data->regs.duty, cdty);
atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm,
atmel_pwm->data->regs.period, cprd);
}
static void atmel_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm,
bool disable_clk)
{
struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
unsigned long timeout;
atmel_pwm_wait_nonpending(atmel_pwm, pwm->hwpwm);
atmel_pwm_writel(atmel_pwm, PWM_DIS, 1 << pwm->hwpwm);
/*
* Wait for the PWM channel disable operation to be effective before
* stopping the clock.
*/
timeout = jiffies + 2 * HZ;
while ((atmel_pwm_readl(atmel_pwm, PWM_SR) & (1 << pwm->hwpwm)) &&
time_before(jiffies, timeout))
usleep_range(10, 100);
if (disable_clk)
clk_disable(atmel_pwm->clk);
}
static int atmel_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
const struct pwm_state *state)
{
struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
struct pwm_state cstate;
unsigned long cprd, cdty;
u32 pres, val;
int ret;
pwm_get_state(pwm, &cstate);
if (state->enabled) {
unsigned long clkrate = clk_get_rate(atmel_pwm->clk);
if (cstate.enabled &&
cstate.polarity == state->polarity &&
cstate.period == state->period) {
u32 cmr = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm, PWM_CMR);
cprd = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm,
atmel_pwm->data->regs.period);
pres = cmr & PWM_CMR_CPRE_MSK;
atmel_pwm_calculate_cdty(state, clkrate, cprd, pres, &cdty);
atmel_pwm_update_cdty(chip, pwm, cdty);
return 0;
}
ret = atmel_pwm_calculate_cprd_and_pres(chip, clkrate, state, &cprd,
&pres);
if (ret) {
dev_err(chip->dev,
"failed to calculate cprd and prescaler\n");
return ret;
}
atmel_pwm_calculate_cdty(state, clkrate, cprd, pres, &cdty);
if (cstate.enabled) {
atmel_pwm_disable(chip, pwm, false);
} else {
ret = clk_enable(atmel_pwm->clk);
if (ret) {
dev_err(chip->dev, "failed to enable clock\n");
return ret;
}
}
/* It is necessary to preserve CPOL, inside CMR */
val = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm, PWM_CMR);
val = (val & ~PWM_CMR_CPRE_MSK) | (pres & PWM_CMR_CPRE_MSK);
if (state->polarity == PWM_POLARITY_NORMAL)
val &= ~PWM_CMR_CPOL;
else
val |= PWM_CMR_CPOL;
atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWM_CMR, val);
atmel_pwm_set_cprd_cdty(chip, pwm, cprd, cdty);
atmel_pwm_writel(atmel_pwm, PWM_ENA, 1 << pwm->hwpwm);
} else if (cstate.enabled) {
atmel_pwm_disable(chip, pwm, true);
}
return 0;
}
static void atmel_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
struct pwm_state *state)
{
struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
u32 sr, cmr;
sr = atmel_pwm_readl(atmel_pwm, PWM_SR);
cmr = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm, PWM_CMR);
if (sr & (1 << pwm->hwpwm)) {
unsigned long rate = clk_get_rate(atmel_pwm->clk);
u32 cdty, cprd, pres;
u64 tmp;
pres = cmr & PWM_CMR_CPRE_MSK;
cprd = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm,
atmel_pwm->data->regs.period);
tmp = (u64)cprd * NSEC_PER_SEC;
tmp <<= pres;
state->period = DIV64_U64_ROUND_UP(tmp, rate);
/* Wait for an updated duty_cycle queued in hardware */
atmel_pwm_wait_nonpending(atmel_pwm, pwm->hwpwm);
cdty = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm,
atmel_pwm->data->regs.duty);
tmp = (u64)(cprd - cdty) * NSEC_PER_SEC;
tmp <<= pres;
state->duty_cycle = DIV64_U64_ROUND_UP(tmp, rate);
state->enabled = true;
} else {
state->enabled = false;
}
if (cmr & PWM_CMR_CPOL)
state->polarity = PWM_POLARITY_INVERSED;
else
state->polarity = PWM_POLARITY_NORMAL;
}
static const struct pwm_ops atmel_pwm_ops = {
.apply = atmel_pwm_apply,
.get_state = atmel_pwm_get_state,
.owner = THIS_MODULE,
};
static const struct atmel_pwm_data atmel_sam9rl_pwm_data = {
.regs = {
.period = PWMV1_CPRD,
.period_upd = PWMV1_CUPD,
.duty = PWMV1_CDTY,
.duty_upd = PWMV1_CUPD,
},
.cfg = {
/* 16 bits to keep period and duty. */
.period_bits = 16,
},
};
static const struct atmel_pwm_data atmel_sama5_pwm_data = {
.regs = {
.period = PWMV2_CPRD,
.period_upd = PWMV2_CPRDUPD,
.duty = PWMV2_CDTY,
.duty_upd = PWMV2_CDTYUPD,
},
.cfg = {
/* 16 bits to keep period and duty. */
.period_bits = 16,
},
};
static const struct atmel_pwm_data mchp_sam9x60_pwm_data = {
.regs = {
.period = PWMV1_CPRD,
.period_upd = PWMV1_CUPD,
.duty = PWMV1_CDTY,
.duty_upd = PWMV1_CUPD,
},
.cfg = {
/* 32 bits to keep period and duty. */
.period_bits = 32,
},
};
static const struct of_device_id atmel_pwm_dt_ids[] = {
{
.compatible = "atmel,at91sam9rl-pwm",
.data = &atmel_sam9rl_pwm_data,
}, {
.compatible = "atmel,sama5d3-pwm",
.data = &atmel_sama5_pwm_data,
}, {
.compatible = "atmel,sama5d2-pwm",
.data = &atmel_sama5_pwm_data,
}, {
.compatible = "microchip,sam9x60-pwm",
.data = &mchp_sam9x60_pwm_data,
}, {
/* sentinel */
},
};
MODULE_DEVICE_TABLE(of, atmel_pwm_dt_ids);
static int atmel_pwm_probe(struct platform_device *pdev)
{
struct atmel_pwm_chip *atmel_pwm;
int ret;
atmel_pwm = devm_kzalloc(&pdev->dev, sizeof(*atmel_pwm), GFP_KERNEL);
if (!atmel_pwm)
return -ENOMEM;
atmel_pwm->data = of_device_get_match_data(&pdev->dev);
atmel_pwm->update_pending = 0;
spin_lock_init(&atmel_pwm->lock);
atmel_pwm->base = devm_platform_ioremap_resource(pdev, 0);
if (IS_ERR(atmel_pwm->base))
return PTR_ERR(atmel_pwm->base);
atmel_pwm->clk = devm_clk_get(&pdev->dev, NULL);
if (IS_ERR(atmel_pwm->clk))
return PTR_ERR(atmel_pwm->clk);
ret = clk_prepare(atmel_pwm->clk);
if (ret) {
dev_err(&pdev->dev, "failed to prepare PWM clock\n");
return ret;
}
atmel_pwm->chip.dev = &pdev->dev;
atmel_pwm->chip.ops = &atmel_pwm_ops;
atmel_pwm->chip.npwm = 4;
ret = pwmchip_add(&atmel_pwm->chip);
if (ret < 0) {
dev_err(&pdev->dev, "failed to add PWM chip %d\n", ret);
goto unprepare_clk;
}
platform_set_drvdata(pdev, atmel_pwm);
return ret;
unprepare_clk:
clk_unprepare(atmel_pwm->clk);
return ret;
}
static int atmel_pwm_remove(struct platform_device *pdev)
{
struct atmel_pwm_chip *atmel_pwm = platform_get_drvdata(pdev);
pwmchip_remove(&atmel_pwm->chip);
clk_unprepare(atmel_pwm->clk);
return 0;
}
static struct platform_driver atmel_pwm_driver = {
.driver = {
.name = "atmel-pwm",
.of_match_table = of_match_ptr(atmel_pwm_dt_ids),
},
.probe = atmel_pwm_probe,
.remove = atmel_pwm_remove,
};
module_platform_driver(atmel_pwm_driver);
MODULE_ALIAS("platform:atmel-pwm");
MODULE_AUTHOR("Bo Shen <voice.shen@atmel.com>");
MODULE_DESCRIPTION("Atmel PWM driver");
MODULE_LICENSE("GPL v2");