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linux/drivers/pwm/pwm-stmpe.c
Linus Walleij ef1f09eca7 pwm: Add a driver for the STMPE PWM 
This adds a driver for the PWM block found in chips of the STMPE 24xx
series of multi-purpose I2C expanders. (I think STMPE means ST
Microelectronics Multi-Purpose Expander.) This PWM was designed in
accordance with Nokia specifications and is kind of weird and usually
just switched between max and zero duty cycle. However it is indeed a
PWM so it needs to live in the PWM subsystem.

This PWM is mostly used for white LED backlight.

Cc: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
2016-07-11 12:49:29 +02:00

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/*
* Copyright (C) 2016 Linaro Ltd.
*
* Author: Linus Walleij <linus.walleij@linaro.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2, as
* published by the Free Software Foundation.
*
*/
#include <linux/bitops.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/mfd/stmpe.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>
#include <linux/slab.h>
#define STMPE24XX_PWMCS 0x30
#define PWMCS_EN_PWM0 BIT(0)
#define PWMCS_EN_PWM1 BIT(1)
#define PWMCS_EN_PWM2 BIT(2)
#define STMPE24XX_PWMIC0 0x38
#define STMPE24XX_PWMIC1 0x39
#define STMPE24XX_PWMIC2 0x3a
#define STMPE_PWM_24XX_PINBASE 21
struct stmpe_pwm {
struct stmpe *stmpe;
struct pwm_chip chip;
u8 last_duty;
};
static inline struct stmpe_pwm *to_stmpe_pwm(struct pwm_chip *chip)
{
return container_of(chip, struct stmpe_pwm, chip);
}
static int stmpe_24xx_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
struct stmpe_pwm *stmpe_pwm = to_stmpe_pwm(chip);
u8 value;
int ret;
ret = stmpe_reg_read(stmpe_pwm->stmpe, STMPE24XX_PWMCS);
if (ret < 0) {
dev_err(chip->dev, "error reading PWM#%u control\n",
pwm->hwpwm);
return ret;
}
value = ret | BIT(pwm->hwpwm);
ret = stmpe_reg_write(stmpe_pwm->stmpe, STMPE24XX_PWMCS, value);
if (ret) {
dev_err(chip->dev, "error writing PWM#%u control\n",
pwm->hwpwm);
return ret;
}
return 0;
}
static void stmpe_24xx_pwm_disable(struct pwm_chip *chip,
struct pwm_device *pwm)
{
struct stmpe_pwm *stmpe_pwm = to_stmpe_pwm(chip);
u8 value;
int ret;
ret = stmpe_reg_read(stmpe_pwm->stmpe, STMPE24XX_PWMCS);
if (ret < 0) {
dev_err(chip->dev, "error reading PWM#%u control\n",
pwm->hwpwm);
return;
}
value = ret & ~BIT(pwm->hwpwm);
ret = stmpe_reg_write(stmpe_pwm->stmpe, STMPE24XX_PWMCS, value);
if (ret) {
dev_err(chip->dev, "error writing PWM#%u control\n",
pwm->hwpwm);
return;
}
}
/* STMPE 24xx PWM instructions */
#define SMAX 0x007f
#define SMIN 0x00ff
#define GTS 0x0000
#define LOAD BIT(14) /* Only available on 2403 */
#define RAMPUP 0x0000
#define RAMPDOWN BIT(7)
#define PRESCALE_512 BIT(14)
#define STEPTIME_1 BIT(8)
#define BRANCH (BIT(15) | BIT(13))
static int stmpe_24xx_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
int duty_ns, int period_ns)
{
struct stmpe_pwm *stmpe_pwm = to_stmpe_pwm(chip);
unsigned int i, pin;
u16 program[3] = {
SMAX,
GTS,
GTS,
};
u8 offset;
int ret;
/* Make sure we are disabled */
if (pwm_is_enabled(pwm)) {
stmpe_24xx_pwm_disable(chip, pwm);
} else {
/* Connect the PWM to the pin */
pin = pwm->hwpwm;
/* On STMPE2401 and 2403 pins 21,22,23 are used */
if (stmpe_pwm->stmpe->partnum == STMPE2401 ||
stmpe_pwm->stmpe->partnum == STMPE2403)
pin += STMPE_PWM_24XX_PINBASE;
ret = stmpe_set_altfunc(stmpe_pwm->stmpe, BIT(pin),
STMPE_BLOCK_PWM);
if (ret) {
dev_err(chip->dev, "unable to connect PWM#%u to pin\n",
pwm->hwpwm);
return ret;
}
}
/* STMPE24XX */
switch (pwm->hwpwm) {
case 0:
offset = STMPE24XX_PWMIC0;
break;
case 1:
offset = STMPE24XX_PWMIC1;
break;
case 2:
offset = STMPE24XX_PWMIC1;
break;
default:
/* Should not happen as npwm is 3 */
return -ENODEV;
}
dev_dbg(chip->dev, "PWM#%u: config duty %d ns, period %d ns\n",
pwm->hwpwm, duty_ns, period_ns);
if (duty_ns == 0) {
if (stmpe_pwm->stmpe->partnum == STMPE2401)
program[0] = SMAX; /* off all the time */
if (stmpe_pwm->stmpe->partnum == STMPE2403)
program[0] = LOAD | 0xff; /* LOAD 0xff */
stmpe_pwm->last_duty = 0x00;
} else if (duty_ns == period_ns) {
if (stmpe_pwm->stmpe->partnum == STMPE2401)
program[0] = SMIN; /* on all the time */
if (stmpe_pwm->stmpe->partnum == STMPE2403)
program[0] = LOAD | 0x00; /* LOAD 0x00 */
stmpe_pwm->last_duty = 0xff;
} else {
u8 value, last = stmpe_pwm->last_duty;
unsigned long duty;
/*
* Counter goes from 0x00 to 0xff repeatedly at 32768 Hz,
* (means a period of 30517 ns) then this is compared to the
* counter from the ramp, if this is >= PWM counter the output
* is high. With LOAD we can define how much of the cycle it
* is on.
*
* Prescale = 0 -> 2 kHz -> T = 1/f = 488281.25 ns
*/
/* Scale to 0..0xff */
duty = duty_ns * 256;
duty = DIV_ROUND_CLOSEST(duty, period_ns);
value = duty;
if (value == last) {
/* Run the old program */
if (pwm_is_enabled(pwm))
stmpe_24xx_pwm_enable(chip, pwm);
return 0;
} else if (stmpe_pwm->stmpe->partnum == STMPE2403) {
/* STMPE2403 can simply set the right PWM value */
program[0] = LOAD | value;
program[1] = 0x0000;
} else if (stmpe_pwm->stmpe->partnum == STMPE2401) {
/* STMPE2401 need a complex program */
u16 incdec = 0x0000;
if (last < value)
/* Count up */
incdec = RAMPUP | (value - last);
else
/* Count down */
incdec = RAMPDOWN | (last - value);
/* Step to desired value, smoothly */
program[0] = PRESCALE_512 | STEPTIME_1 | incdec;
/* Loop eternally to 0x00 */
program[1] = BRANCH;
}
dev_dbg(chip->dev,
"PWM#%u: value = %02x, last_duty = %02x, program=%04x,%04x,%04x\n",
pwm->hwpwm, value, last, program[0], program[1],
program[2]);
stmpe_pwm->last_duty = value;
}
/*
* We can write programs of up to 64 16-bit words into this channel.
*/
for (i = 0; i < ARRAY_SIZE(program); i++) {
u8 value;
value = (program[i] >> 8) & 0xff;
ret = stmpe_reg_write(stmpe_pwm->stmpe, offset, value);
if (ret) {
dev_err(chip->dev, "error writing register %02x: %d\n",
offset, ret);
return ret;
}
value = program[i] & 0xff;
ret = stmpe_reg_write(stmpe_pwm->stmpe, offset, value);
if (ret) {
dev_err(chip->dev, "error writing register %02x: %d\n",
offset, ret);
return ret;
}
}
/* If we were enabled, re-enable this PWM */
if (pwm_is_enabled(pwm))
stmpe_24xx_pwm_enable(chip, pwm);
/* Sleep for 200ms so we're sure it will take effect */
msleep(200);
dev_dbg(chip->dev, "programmed PWM#%u, %u bytes\n", pwm->hwpwm, i);
return 0;
}
static const struct pwm_ops stmpe_24xx_pwm_ops = {
.config = stmpe_24xx_pwm_config,
.enable = stmpe_24xx_pwm_enable,
.disable = stmpe_24xx_pwm_disable,
.owner = THIS_MODULE,
};
static int __init stmpe_pwm_probe(struct platform_device *pdev)
{
struct stmpe *stmpe = dev_get_drvdata(pdev->dev.parent);
struct stmpe_pwm *pwm;
int ret;
pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);
if (!pwm)
return -ENOMEM;
pwm->stmpe = stmpe;
pwm->chip.dev = &pdev->dev;
pwm->chip.base = -1;
if (stmpe->partnum == STMPE2401 || stmpe->partnum == STMPE2403) {
pwm->chip.ops = &stmpe_24xx_pwm_ops;
pwm->chip.npwm = 3;
} else {
if (stmpe->partnum == STMPE1601)
dev_err(&pdev->dev, "STMPE1601 not yet supported\n");
else
dev_err(&pdev->dev, "Unknown STMPE PWM\n");
return -ENODEV;
}
ret = stmpe_enable(stmpe, STMPE_BLOCK_PWM);
if (ret)
return ret;
ret = pwmchip_add(&pwm->chip);
if (ret) {
stmpe_disable(stmpe, STMPE_BLOCK_PWM);
return ret;
}
platform_set_drvdata(pdev, pwm);
return 0;
}
static struct platform_driver stmpe_pwm_driver = {
.driver = {
.name = "stmpe-pwm",
},
};
builtin_platform_driver_probe(stmpe_pwm_driver, stmpe_pwm_probe);
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