Commit ef1f09ec authored by Linus Walleij's avatar Linus Walleij Committed by Thierry Reding
Browse files

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: default avatarLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: default avatarThierry Reding <thierry.reding@gmail.com>
parent 27e8c8f3

drivers/pwm/Kconfig

+7 −0
Original line number Diff line number Diff line
@@ -372,6 +372,13 @@ config PWM_STI 
	  To compile this driver as a module, choose M here: the module

	  will be called pwm-sti.



config PWM_STMPE

	bool "STMPE expander PWM export"

	depends on MFD_STMPE

	help

	  This enables support for the PWMs found in the STMPE I/O

	  expanders.



config PWM_SUN4I

	tristate "Allwinner PWM support"

	depends on ARCH_SUNXI || COMPILE_TEST

drivers/pwm/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -35,6 +35,7 @@ obj-$(CONFIG_PWM_ROCKCHIP) += pwm-rockchip.o 
obj-$(CONFIG_PWM_SAMSUNG)	+= pwm-samsung.o

obj-$(CONFIG_PWM_SPEAR)		+= pwm-spear.o

obj-$(CONFIG_PWM_STI)		+= pwm-sti.o

obj-$(CONFIG_PWM_STMPE)		+= pwm-stmpe.o

obj-$(CONFIG_PWM_SUN4I)		+= pwm-sun4i.o

obj-$(CONFIG_PWM_TEGRA)		+= pwm-tegra.o

obj-$(CONFIG_PWM_TIECAP)	+= pwm-tiecap.o

drivers/pwm/pwm-stmpe.c

0 → 100644
+319 −0
Original line number Diff line number Diff line 
/*

 * 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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