linux/drivers/pwm/pwm-atmel.c
Alexandre Belloni 472ac3dcac pwm: atmel: Fix incorrect CDTY value after disabling
pwm-leds calls .config() and .disable() in a row. This exhibits that it
may happen that the channel gets disabled before CDTY has been updated
with CUPD. The issue gets quite worse with long periods. So, ensure that
at least one period has past before disabling the channel by polling
ISR.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Tested-by: Gaël PORTAY <gael.portay@gmail.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
2015-06-12 11:16:12 +02:00

429 lines
11 KiB
C

/*
* Driver for Atmel Pulse Width Modulation Controller
*
* Copyright (C) 2013 Atmel Corporation
* Bo Shen <voice.shen@atmel.com>
*
* Licensed under GPLv2.
*/
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/mutex.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
/*
* Max value for duty and period
*
* Although the duty and period register is 32 bit,
* however only the LSB 16 bits are significant.
*/
#define PWM_MAX_DTY 0xFFFF
#define PWM_MAX_PRD 0xFFFF
#define PRD_MAX_PRES 10
struct atmel_pwm_chip {
struct pwm_chip chip;
struct clk *clk;
void __iomem *base;
unsigned int updated_pwms;
struct mutex isr_lock; /* ISR is cleared when read, ensure only one thread does that */
void (*config)(struct pwm_chip *chip, struct pwm_device *pwm,
unsigned long dty, unsigned long prd);
};
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 readl_relaxed(chip->base + 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;
writel_relaxed(val, chip->base + base + offset);
}
static int atmel_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
int duty_ns, int period_ns)
{
struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
unsigned long prd, dty;
unsigned long long div;
unsigned int pres = 0;
u32 val;
int ret;
if (test_bit(PWMF_ENABLED, &pwm->flags) && (period_ns != pwm->period)) {
dev_err(chip->dev, "cannot change PWM period while enabled\n");
return -EBUSY;
}
/* Calculate the period cycles and prescale value */
div = (unsigned long long)clk_get_rate(atmel_pwm->clk) * period_ns;
do_div(div, NSEC_PER_SEC);
while (div > PWM_MAX_PRD) {
div >>= 1;
pres++;
}
if (pres > PRD_MAX_PRES) {
dev_err(chip->dev, "pres exceeds the maximum value\n");
return -EINVAL;
}
/* Calculate the duty cycles */
prd = div;
div *= duty_ns;
do_div(div, period_ns);
dty = prd - div;
ret = clk_enable(atmel_pwm->clk);
if (ret) {
dev_err(chip->dev, "failed to enable PWM 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);
atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWM_CMR, val);
atmel_pwm->config(chip, pwm, dty, prd);
mutex_lock(&atmel_pwm->isr_lock);
atmel_pwm->updated_pwms |= atmel_pwm_readl(atmel_pwm, PWM_ISR);
atmel_pwm->updated_pwms &= ~(1 << pwm->hwpwm);
mutex_unlock(&atmel_pwm->isr_lock);
clk_disable(atmel_pwm->clk);
return ret;
}
static void atmel_pwm_config_v1(struct pwm_chip *chip, struct pwm_device *pwm,
unsigned long dty, unsigned long prd)
{
struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
unsigned int val;
atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWMV1_CUPD, dty);
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);
/*
* If the PWM channel is enabled, only update CDTY by using the update
* register, it needs to set bit 10 of CMR to 0
*/
if (test_bit(PWMF_ENABLED, &pwm->flags))
return;
/*
* If the PWM channel is disabled, write value to duty and period
* registers directly.
*/
atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWMV1_CDTY, dty);
atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWMV1_CPRD, prd);
}
static void atmel_pwm_config_v2(struct pwm_chip *chip, struct pwm_device *pwm,
unsigned long dty, unsigned long prd)
{
struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
if (test_bit(PWMF_ENABLED, &pwm->flags)) {
/*
* If the PWM channel is enabled, using the duty update register
* to update the value.
*/
atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWMV2_CDTYUPD, dty);
} else {
/*
* If the PWM channel is disabled, write value to duty and
* period registers directly.
*/
atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWMV2_CDTY, dty);
atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWMV2_CPRD, prd);
}
}
static int atmel_pwm_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
enum pwm_polarity polarity)
{
struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
u32 val;
int ret;
val = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm, PWM_CMR);
if (polarity == PWM_POLARITY_NORMAL)
val &= ~PWM_CMR_CPOL;
else
val |= PWM_CMR_CPOL;
ret = clk_enable(atmel_pwm->clk);
if (ret) {
dev_err(chip->dev, "failed to enable PWM clock\n");
return ret;
}
atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWM_CMR, val);
clk_disable(atmel_pwm->clk);
return 0;
}
static int atmel_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
int ret;
ret = clk_enable(atmel_pwm->clk);
if (ret) {
dev_err(chip->dev, "failed to enable PWM clock\n");
return ret;
}
atmel_pwm_writel(atmel_pwm, PWM_ENA, 1 << pwm->hwpwm);
return 0;
}
static void atmel_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
{
struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
unsigned long timeout = jiffies + 2 * HZ;
/*
* Wait for at least a complete period to have passed before disabling a
* channel to be sure that CDTY has been updated
*/
mutex_lock(&atmel_pwm->isr_lock);
atmel_pwm->updated_pwms |= atmel_pwm_readl(atmel_pwm, PWM_ISR);
while (!(atmel_pwm->updated_pwms & (1 << pwm->hwpwm)) &&
time_before(jiffies, timeout)) {
usleep_range(10, 100);
atmel_pwm->updated_pwms |= atmel_pwm_readl(atmel_pwm, PWM_ISR);
}
mutex_unlock(&atmel_pwm->isr_lock);
atmel_pwm_writel(atmel_pwm, PWM_DIS, 1 << pwm->hwpwm);
clk_disable(atmel_pwm->clk);
}
static const struct pwm_ops atmel_pwm_ops = {
.config = atmel_pwm_config,
.set_polarity = atmel_pwm_set_polarity,
.enable = atmel_pwm_enable,
.disable = atmel_pwm_disable,
.owner = THIS_MODULE,
};
struct atmel_pwm_data {
void (*config)(struct pwm_chip *chip, struct pwm_device *pwm,
unsigned long dty, unsigned long prd);
};
static const struct atmel_pwm_data atmel_pwm_data_v1 = {
.config = atmel_pwm_config_v1,
};
static const struct atmel_pwm_data atmel_pwm_data_v2 = {
.config = atmel_pwm_config_v2,
};
static const struct platform_device_id atmel_pwm_devtypes[] = {
{
.name = "at91sam9rl-pwm",
.driver_data = (kernel_ulong_t)&atmel_pwm_data_v1,
}, {
.name = "sama5d3-pwm",
.driver_data = (kernel_ulong_t)&atmel_pwm_data_v2,
}, {
/* sentinel */
},
};
MODULE_DEVICE_TABLE(platform, atmel_pwm_devtypes);
static const struct of_device_id atmel_pwm_dt_ids[] = {
{
.compatible = "atmel,at91sam9rl-pwm",
.data = &atmel_pwm_data_v1,
}, {
.compatible = "atmel,sama5d3-pwm",
.data = &atmel_pwm_data_v2,
}, {
/* sentinel */
},
};
MODULE_DEVICE_TABLE(of, atmel_pwm_dt_ids);
static inline const struct atmel_pwm_data *
atmel_pwm_get_driver_data(struct platform_device *pdev)
{
if (pdev->dev.of_node) {
const struct of_device_id *match;
match = of_match_device(atmel_pwm_dt_ids, &pdev->dev);
if (!match)
return NULL;
return match->data;
} else {
const struct platform_device_id *id;
id = platform_get_device_id(pdev);
return (struct atmel_pwm_data *)id->driver_data;
}
}
static int atmel_pwm_probe(struct platform_device *pdev)
{
const struct atmel_pwm_data *data;
struct atmel_pwm_chip *atmel_pwm;
struct resource *res;
int ret;
data = atmel_pwm_get_driver_data(pdev);
if (!data)
return -ENODEV;
atmel_pwm = devm_kzalloc(&pdev->dev, sizeof(*atmel_pwm), GFP_KERNEL);
if (!atmel_pwm)
return -ENOMEM;
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
atmel_pwm->base = devm_ioremap_resource(&pdev->dev, res);
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;
if (pdev->dev.of_node) {
atmel_pwm->chip.of_xlate = of_pwm_xlate_with_flags;
atmel_pwm->chip.of_pwm_n_cells = 3;
}
atmel_pwm->chip.base = -1;
atmel_pwm->chip.npwm = 4;
atmel_pwm->chip.can_sleep = true;
atmel_pwm->config = data->config;
atmel_pwm->updated_pwms = 0;
mutex_init(&atmel_pwm->isr_lock);
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);
clk_unprepare(atmel_pwm->clk);
mutex_destroy(&atmel_pwm->isr_lock);
return pwmchip_remove(&atmel_pwm->chip);
}
static struct platform_driver atmel_pwm_driver = {
.driver = {
.name = "atmel-pwm",
.of_match_table = of_match_ptr(atmel_pwm_dt_ids),
},
.id_table = atmel_pwm_devtypes,
.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");