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>tirimbino
Linus Walleij
9 years ago
committed by
Thierry Reding
parent
27e8c8f351
commit
ef1f09eca7
@ -0,0 +1,319 @@ |
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/*
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* Copyright (C) 2016 Linaro Ltd. |
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* |
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* Author: Linus Walleij <linus.walleij@linaro.org> |
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* |
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* This program is free software; you can redistribute it and/or modify |
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* it under the terms of the GNU General Public License version 2, as |
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* published by the Free Software Foundation. |
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* |
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*/ |
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#include <linux/bitops.h> |
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#include <linux/delay.h> |
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#include <linux/err.h> |
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#include <linux/mfd/stmpe.h> |
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#include <linux/module.h> |
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#include <linux/of.h> |
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#include <linux/platform_device.h> |
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#include <linux/pwm.h> |
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#include <linux/slab.h> |
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#define STMPE24XX_PWMCS 0x30 |
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#define PWMCS_EN_PWM0 BIT(0) |
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#define PWMCS_EN_PWM1 BIT(1) |
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#define PWMCS_EN_PWM2 BIT(2) |
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#define STMPE24XX_PWMIC0 0x38 |
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#define STMPE24XX_PWMIC1 0x39 |
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#define STMPE24XX_PWMIC2 0x3a |
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#define STMPE_PWM_24XX_PINBASE 21 |
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struct stmpe_pwm { |
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struct stmpe *stmpe; |
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struct pwm_chip chip; |
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u8 last_duty; |
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}; |
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static inline struct stmpe_pwm *to_stmpe_pwm(struct pwm_chip *chip) |
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{ |
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return container_of(chip, struct stmpe_pwm, chip); |
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} |
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static int stmpe_24xx_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm) |
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{ |
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struct stmpe_pwm *stmpe_pwm = to_stmpe_pwm(chip); |
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u8 value; |
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int ret; |
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ret = stmpe_reg_read(stmpe_pwm->stmpe, STMPE24XX_PWMCS); |
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if (ret < 0) { |
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dev_err(chip->dev, "error reading PWM#%u control\n", |
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pwm->hwpwm); |
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return ret; |
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} |
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value = ret | BIT(pwm->hwpwm); |
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ret = stmpe_reg_write(stmpe_pwm->stmpe, STMPE24XX_PWMCS, value); |
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if (ret) { |
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dev_err(chip->dev, "error writing PWM#%u control\n", |
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pwm->hwpwm); |
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return ret; |
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} |
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return 0; |
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} |
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static void stmpe_24xx_pwm_disable(struct pwm_chip *chip, |
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struct pwm_device *pwm) |
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{ |
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struct stmpe_pwm *stmpe_pwm = to_stmpe_pwm(chip); |
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u8 value; |
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int ret; |
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ret = stmpe_reg_read(stmpe_pwm->stmpe, STMPE24XX_PWMCS); |
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if (ret < 0) { |
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dev_err(chip->dev, "error reading PWM#%u control\n", |
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pwm->hwpwm); |
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return; |
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} |
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value = ret & ~BIT(pwm->hwpwm); |
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ret = stmpe_reg_write(stmpe_pwm->stmpe, STMPE24XX_PWMCS, value); |
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if (ret) { |
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dev_err(chip->dev, "error writing PWM#%u control\n", |
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pwm->hwpwm); |
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return; |
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} |
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} |
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/* STMPE 24xx PWM instructions */ |
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#define SMAX 0x007f |
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#define SMIN 0x00ff |
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#define GTS 0x0000 |
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#define LOAD BIT(14) /* Only available on 2403 */ |
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#define RAMPUP 0x0000 |
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#define RAMPDOWN BIT(7) |
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#define PRESCALE_512 BIT(14) |
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#define STEPTIME_1 BIT(8) |
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#define BRANCH (BIT(15) | BIT(13)) |
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static int stmpe_24xx_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, |
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int duty_ns, int period_ns) |
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{ |
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struct stmpe_pwm *stmpe_pwm = to_stmpe_pwm(chip); |
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unsigned int i, pin; |
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u16 program[3] = { |
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SMAX, |
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GTS, |
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GTS, |
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}; |
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u8 offset; |
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int ret; |
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/* Make sure we are disabled */ |
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if (pwm_is_enabled(pwm)) { |
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stmpe_24xx_pwm_disable(chip, pwm); |
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} else { |
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/* Connect the PWM to the pin */ |
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pin = pwm->hwpwm; |
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/* On STMPE2401 and 2403 pins 21,22,23 are used */ |
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if (stmpe_pwm->stmpe->partnum == STMPE2401 || |
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stmpe_pwm->stmpe->partnum == STMPE2403) |
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pin += STMPE_PWM_24XX_PINBASE; |
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ret = stmpe_set_altfunc(stmpe_pwm->stmpe, BIT(pin), |
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STMPE_BLOCK_PWM); |
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if (ret) { |
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dev_err(chip->dev, "unable to connect PWM#%u to pin\n", |
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pwm->hwpwm); |
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return ret; |
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} |
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} |
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/* STMPE24XX */ |
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switch (pwm->hwpwm) { |
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case 0: |
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offset = STMPE24XX_PWMIC0; |
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break; |
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case 1: |
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offset = STMPE24XX_PWMIC1; |
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break; |
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case 2: |
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offset = STMPE24XX_PWMIC1; |
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break; |
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default: |
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/* Should not happen as npwm is 3 */ |
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return -ENODEV; |
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} |
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dev_dbg(chip->dev, "PWM#%u: config duty %d ns, period %d ns\n", |
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pwm->hwpwm, duty_ns, period_ns); |
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if (duty_ns == 0) { |
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if (stmpe_pwm->stmpe->partnum == STMPE2401) |
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program[0] = SMAX; /* off all the time */ |
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if (stmpe_pwm->stmpe->partnum == STMPE2403) |
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program[0] = LOAD | 0xff; /* LOAD 0xff */ |
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stmpe_pwm->last_duty = 0x00; |
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} else if (duty_ns == period_ns) { |
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if (stmpe_pwm->stmpe->partnum == STMPE2401) |
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program[0] = SMIN; /* on all the time */ |
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if (stmpe_pwm->stmpe->partnum == STMPE2403) |
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program[0] = LOAD | 0x00; /* LOAD 0x00 */ |
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stmpe_pwm->last_duty = 0xff; |
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} else { |
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u8 value, last = stmpe_pwm->last_duty; |
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unsigned long duty; |
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/*
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* Counter goes from 0x00 to 0xff repeatedly at 32768 Hz, |
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* (means a period of 30517 ns) then this is compared to the |
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* counter from the ramp, if this is >= PWM counter the output |
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* is high. With LOAD we can define how much of the cycle it |
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* is on. |
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* |
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* Prescale = 0 -> 2 kHz -> T = 1/f = 488281.25 ns |
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*/ |
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/* Scale to 0..0xff */ |
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duty = duty_ns * 256; |
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duty = DIV_ROUND_CLOSEST(duty, period_ns); |
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value = duty; |
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if (value == last) { |
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/* Run the old program */ |
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if (pwm_is_enabled(pwm)) |
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stmpe_24xx_pwm_enable(chip, pwm); |
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return 0; |
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} else if (stmpe_pwm->stmpe->partnum == STMPE2403) { |
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/* STMPE2403 can simply set the right PWM value */ |
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program[0] = LOAD | value; |
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program[1] = 0x0000; |
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} else if (stmpe_pwm->stmpe->partnum == STMPE2401) { |
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/* STMPE2401 need a complex program */ |
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u16 incdec = 0x0000; |
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if (last < value) |
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/* Count up */ |
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incdec = RAMPUP | (value - last); |
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else |
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/* Count down */ |
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incdec = RAMPDOWN | (last - value); |
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/* Step to desired value, smoothly */ |
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program[0] = PRESCALE_512 | STEPTIME_1 | incdec; |
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/* Loop eternally to 0x00 */ |
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program[1] = BRANCH; |
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} |
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dev_dbg(chip->dev, |
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"PWM#%u: value = %02x, last_duty = %02x, program=%04x,%04x,%04x\n", |
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pwm->hwpwm, value, last, program[0], program[1], |
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program[2]); |
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stmpe_pwm->last_duty = value; |
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} |
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/*
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* We can write programs of up to 64 16-bit words into this channel. |
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*/ |
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for (i = 0; i < ARRAY_SIZE(program); i++) { |
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u8 value; |
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value = (program[i] >> 8) & 0xff; |
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ret = stmpe_reg_write(stmpe_pwm->stmpe, offset, value); |
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if (ret) { |
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dev_err(chip->dev, "error writing register %02x: %d\n", |
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offset, ret); |
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return ret; |
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} |
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value = program[i] & 0xff; |
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ret = stmpe_reg_write(stmpe_pwm->stmpe, offset, value); |
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if (ret) { |
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dev_err(chip->dev, "error writing register %02x: %d\n", |
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offset, ret); |
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return ret; |
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} |
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} |
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/* If we were enabled, re-enable this PWM */ |
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if (pwm_is_enabled(pwm)) |
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stmpe_24xx_pwm_enable(chip, pwm); |
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/* Sleep for 200ms so we're sure it will take effect */ |
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msleep(200); |
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dev_dbg(chip->dev, "programmed PWM#%u, %u bytes\n", pwm->hwpwm, i); |
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return 0; |
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} |
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static const struct pwm_ops stmpe_24xx_pwm_ops = { |
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.config = stmpe_24xx_pwm_config, |
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.enable = stmpe_24xx_pwm_enable, |
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.disable = stmpe_24xx_pwm_disable, |
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.owner = THIS_MODULE, |
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}; |
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static int __init stmpe_pwm_probe(struct platform_device *pdev) |
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{ |
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struct stmpe *stmpe = dev_get_drvdata(pdev->dev.parent); |
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struct stmpe_pwm *pwm; |
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int ret; |
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pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL); |
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if (!pwm) |
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return -ENOMEM; |
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pwm->stmpe = stmpe; |
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pwm->chip.dev = &pdev->dev; |
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pwm->chip.base = -1; |
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if (stmpe->partnum == STMPE2401 || stmpe->partnum == STMPE2403) { |
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pwm->chip.ops = &stmpe_24xx_pwm_ops; |
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pwm->chip.npwm = 3; |
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} else { |
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if (stmpe->partnum == STMPE1601) |
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dev_err(&pdev->dev, "STMPE1601 not yet supported\n"); |
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else |
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dev_err(&pdev->dev, "Unknown STMPE PWM\n"); |
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return -ENODEV; |
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} |
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ret = stmpe_enable(stmpe, STMPE_BLOCK_PWM); |
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if (ret) |
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return ret; |
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ret = pwmchip_add(&pwm->chip); |
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if (ret) { |
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stmpe_disable(stmpe, STMPE_BLOCK_PWM); |
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return ret; |
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} |
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platform_set_drvdata(pdev, pwm); |
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return 0; |
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} |
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static struct platform_driver stmpe_pwm_driver = { |
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.driver = { |
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.name = "stmpe-pwm", |
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}, |
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}; |
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builtin_platform_driver_probe(stmpe_pwm_driver, stmpe_pwm_probe); |
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