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remarkable-linux/drivers/pwm/pwm-twl.c
Paul Kocialkowski 45c0ce847a pwm: twl: Reliably disable TWL6030 PWMs 
The current TWL6030 code for the TWL PWM driver does not reliably disable the
PWM output, as tested with LEDs. The previous commit to that driver introduced
that regression.

However, it does make sense to disable the PWM clock after resetting the PWM,
but for some obscure reason, doing it all at once simply doesn't work.

The TWL6030 datasheet mentions that PWMs have to be disabled in two distinct
steps. However, clearing the clock enable bit in a second step (after issuing a
reset first) does not work.

The only approach that works is the one that was in place before the previous
commit to the driver. It consists in enabling the PWM clock after issuing a
reset. This is what TI kernel trees and production code seem to be using.

However, adding an extra step to disable the PWM clock seems to work reliably,
despite looking quite odd.

Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
Acked-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
2016-09-05 07:13:47 +02:00

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/*
* Driver for TWL4030/6030 Generic Pulse Width Modulator
*
* Copyright (C) 2012 Texas Instruments
* Author: Peter Ujfalusi <peter.ujfalusi@ti.com>
*
* 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.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License along with
* this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pwm.h>
#include <linux/i2c/twl.h>
#include <linux/slab.h>
/*
* This driver handles the PWMs of TWL4030 and TWL6030.
* The TRM names for the PWMs on TWL4030 are: PWM0, PWM1
* TWL6030 also have two PWMs named in the TRM as PWM1, PWM2
*/
#define TWL_PWM_MAX 0x7f
/* Registers, bits and macro for TWL4030 */
#define TWL4030_GPBR1_REG 0x0c
#define TWL4030_PMBR1_REG 0x0d
/* GPBR1 register bits */
#define TWL4030_PWMXCLK_ENABLE (1 << 0)
#define TWL4030_PWMX_ENABLE (1 << 2)
#define TWL4030_PWMX_BITS (TWL4030_PWMX_ENABLE | TWL4030_PWMXCLK_ENABLE)
#define TWL4030_PWM_TOGGLE(pwm, x) ((x) << (pwm))
/* PMBR1 register bits */
#define TWL4030_GPIO6_PWM0_MUTE_MASK (0x03 << 2)
#define TWL4030_GPIO6_PWM0_MUTE_PWM0 (0x01 << 2)
#define TWL4030_GPIO7_VIBRASYNC_PWM1_MASK (0x03 << 4)
#define TWL4030_GPIO7_VIBRASYNC_PWM1_PWM1 (0x03 << 4)
/* Register, bits and macro for TWL6030 */
#define TWL6030_TOGGLE3_REG 0x92
#define TWL6030_PWMXR (1 << 0)
#define TWL6030_PWMXS (1 << 1)
#define TWL6030_PWMXEN (1 << 2)
#define TWL6030_PWM_TOGGLE(pwm, x) ((x) << (pwm * 3))
struct twl_pwm_chip {
struct pwm_chip chip;
struct mutex mutex;
u8 twl6030_toggle3;
u8 twl4030_pwm_mux;
};
static inline struct twl_pwm_chip *to_twl(struct pwm_chip *chip)
{
return container_of(chip, struct twl_pwm_chip, chip);
}
static int twl_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
int duty_ns, int period_ns)
{
int duty_cycle = DIV_ROUND_UP(duty_ns * TWL_PWM_MAX, period_ns) + 1;
u8 pwm_config[2] = { 1, 0 };
int base, ret;
/*
* To configure the duty period:
* On-cycle is set to 1 (the minimum allowed value)
* The off time of 0 is not configurable, so the mapping is:
* 0 -> off cycle = 2,
* 1 -> off cycle = 2,
* 2 -> off cycle = 3,
* 126 - > off cycle 127,
* 127 - > off cycle 1
* When on cycle == off cycle the PWM will be always on
*/
if (duty_cycle == 1)
duty_cycle = 2;
else if (duty_cycle > TWL_PWM_MAX)
duty_cycle = 1;
base = pwm->hwpwm * 3;
pwm_config[1] = duty_cycle;
ret = twl_i2c_write(TWL_MODULE_PWM, pwm_config, base, 2);
if (ret < 0)
dev_err(chip->dev, "%s: Failed to configure PWM\n", pwm->label);
return ret;
}
static int twl4030_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
struct twl_pwm_chip *twl = to_twl(chip);
int ret;
u8 val;
mutex_lock(&twl->mutex);
ret = twl_i2c_read_u8(TWL4030_MODULE_INTBR, &val, TWL4030_GPBR1_REG);
if (ret < 0) {
dev_err(chip->dev, "%s: Failed to read GPBR1\n", pwm->label);
goto out;
}
val |= TWL4030_PWM_TOGGLE(pwm->hwpwm, TWL4030_PWMXCLK_ENABLE);
ret = twl_i2c_write_u8(TWL4030_MODULE_INTBR, val, TWL4030_GPBR1_REG);
if (ret < 0)
dev_err(chip->dev, "%s: Failed to enable PWM\n", pwm->label);
val |= TWL4030_PWM_TOGGLE(pwm->hwpwm, TWL4030_PWMX_ENABLE);
ret = twl_i2c_write_u8(TWL4030_MODULE_INTBR, val, TWL4030_GPBR1_REG);
if (ret < 0)
dev_err(chip->dev, "%s: Failed to enable PWM\n", pwm->label);
out:
mutex_unlock(&twl->mutex);
return ret;
}
static void twl4030_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
{
struct twl_pwm_chip *twl = to_twl(chip);
int ret;
u8 val;
mutex_lock(&twl->mutex);
ret = twl_i2c_read_u8(TWL4030_MODULE_INTBR, &val, TWL4030_GPBR1_REG);
if (ret < 0) {
dev_err(chip->dev, "%s: Failed to read GPBR1\n", pwm->label);
goto out;
}
val &= ~TWL4030_PWM_TOGGLE(pwm->hwpwm, TWL4030_PWMX_ENABLE);
ret = twl_i2c_write_u8(TWL4030_MODULE_INTBR, val, TWL4030_GPBR1_REG);
if (ret < 0)
dev_err(chip->dev, "%s: Failed to disable PWM\n", pwm->label);
val &= ~TWL4030_PWM_TOGGLE(pwm->hwpwm, TWL4030_PWMXCLK_ENABLE);
ret = twl_i2c_write_u8(TWL4030_MODULE_INTBR, val, TWL4030_GPBR1_REG);
if (ret < 0)
dev_err(chip->dev, "%s: Failed to disable PWM\n", pwm->label);
out:
mutex_unlock(&twl->mutex);
}
static int twl4030_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
{
struct twl_pwm_chip *twl = to_twl(chip);
int ret;
u8 val, mask, bits;
if (pwm->hwpwm == 1) {
mask = TWL4030_GPIO7_VIBRASYNC_PWM1_MASK;
bits = TWL4030_GPIO7_VIBRASYNC_PWM1_PWM1;
} else {
mask = TWL4030_GPIO6_PWM0_MUTE_MASK;
bits = TWL4030_GPIO6_PWM0_MUTE_PWM0;
}
mutex_lock(&twl->mutex);
ret = twl_i2c_read_u8(TWL4030_MODULE_INTBR, &val, TWL4030_PMBR1_REG);
if (ret < 0) {
dev_err(chip->dev, "%s: Failed to read PMBR1\n", pwm->label);
goto out;
}
/* Save the current MUX configuration for the PWM */
twl->twl4030_pwm_mux &= ~mask;
twl->twl4030_pwm_mux |= (val & mask);
/* Select PWM functionality */
val &= ~mask;
val |= bits;
ret = twl_i2c_write_u8(TWL4030_MODULE_INTBR, val, TWL4030_PMBR1_REG);
if (ret < 0)
dev_err(chip->dev, "%s: Failed to request PWM\n", pwm->label);
out:
mutex_unlock(&twl->mutex);
return ret;
}
static void twl4030_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
{
struct twl_pwm_chip *twl = to_twl(chip);
int ret;
u8 val, mask;
if (pwm->hwpwm == 1)
mask = TWL4030_GPIO7_VIBRASYNC_PWM1_MASK;
else
mask = TWL4030_GPIO6_PWM0_MUTE_MASK;
mutex_lock(&twl->mutex);
ret = twl_i2c_read_u8(TWL4030_MODULE_INTBR, &val, TWL4030_PMBR1_REG);
if (ret < 0) {
dev_err(chip->dev, "%s: Failed to read PMBR1\n", pwm->label);
goto out;
}
/* Restore the MUX configuration for the PWM */
val &= ~mask;
val |= (twl->twl4030_pwm_mux & mask);
ret = twl_i2c_write_u8(TWL4030_MODULE_INTBR, val, TWL4030_PMBR1_REG);
if (ret < 0)
dev_err(chip->dev, "%s: Failed to free PWM\n", pwm->label);
out:
mutex_unlock(&twl->mutex);
}
static int twl6030_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
{
struct twl_pwm_chip *twl = to_twl(chip);
int ret;
u8 val;
mutex_lock(&twl->mutex);
val = twl->twl6030_toggle3;
val |= TWL6030_PWM_TOGGLE(pwm->hwpwm, TWL6030_PWMXS | TWL6030_PWMXEN);
val &= ~TWL6030_PWM_TOGGLE(pwm->hwpwm, TWL6030_PWMXR);
ret = twl_i2c_write_u8(TWL6030_MODULE_ID1, val, TWL6030_TOGGLE3_REG);
if (ret < 0) {
dev_err(chip->dev, "%s: Failed to enable PWM\n", pwm->label);
goto out;
}
twl->twl6030_toggle3 = val;
out:
mutex_unlock(&twl->mutex);
return ret;
}
static void twl6030_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
{
struct twl_pwm_chip *twl = to_twl(chip);
int ret;
u8 val;
mutex_lock(&twl->mutex);
val = twl->twl6030_toggle3;
val |= TWL6030_PWM_TOGGLE(pwm->hwpwm, TWL6030_PWMXR);
val &= ~TWL6030_PWM_TOGGLE(pwm->hwpwm, TWL6030_PWMXS | TWL6030_PWMXEN);
ret = twl_i2c_write_u8(TWL6030_MODULE_ID1, val, TWL6030_TOGGLE3_REG);
if (ret < 0) {
dev_err(chip->dev, "%s: Failed to disable PWM\n", pwm->label);
goto out;
}
val |= TWL6030_PWM_TOGGLE(pwm->hwpwm, TWL6030_PWMXEN);
ret = twl_i2c_write_u8(TWL6030_MODULE_ID1, val, TWL6030_TOGGLE3_REG);
if (ret < 0) {
dev_err(chip->dev, "%s: Failed to disable PWM\n", pwm->label);
goto out;
}
val &= ~TWL6030_PWM_TOGGLE(pwm->hwpwm, TWL6030_PWMXEN);
ret = twl_i2c_write_u8(TWL6030_MODULE_ID1, val, TWL6030_TOGGLE3_REG);
if (ret < 0) {
dev_err(chip->dev, "%s: Failed to disable PWM\n", pwm->label);
goto out;
}
twl->twl6030_toggle3 = val;
out:
mutex_unlock(&twl->mutex);
}
static const struct pwm_ops twl4030_pwm_ops = {
.config = twl_pwm_config,
.enable = twl4030_pwm_enable,
.disable = twl4030_pwm_disable,
.request = twl4030_pwm_request,
.free = twl4030_pwm_free,
.owner = THIS_MODULE,
};
static const struct pwm_ops twl6030_pwm_ops = {
.config = twl_pwm_config,
.enable = twl6030_pwm_enable,
.disable = twl6030_pwm_disable,
.owner = THIS_MODULE,
};
static int twl_pwm_probe(struct platform_device *pdev)
{
struct twl_pwm_chip *twl;
int ret;
twl = devm_kzalloc(&pdev->dev, sizeof(*twl), GFP_KERNEL);
if (!twl)
return -ENOMEM;
if (twl_class_is_4030())
twl->chip.ops = &twl4030_pwm_ops;
else
twl->chip.ops = &twl6030_pwm_ops;
twl->chip.dev = &pdev->dev;
twl->chip.base = -1;
twl->chip.npwm = 2;
twl->chip.can_sleep = true;
mutex_init(&twl->mutex);
ret = pwmchip_add(&twl->chip);
if (ret < 0)
return ret;
platform_set_drvdata(pdev, twl);
return 0;
}
static int twl_pwm_remove(struct platform_device *pdev)
{
struct twl_pwm_chip *twl = platform_get_drvdata(pdev);
return pwmchip_remove(&twl->chip);
}
#ifdef CONFIG_OF
static const struct of_device_id twl_pwm_of_match[] = {
{ .compatible = "ti,twl4030-pwm" },
{ .compatible = "ti,twl6030-pwm" },
{ },
};
MODULE_DEVICE_TABLE(of, twl_pwm_of_match);
#endif
static struct platform_driver twl_pwm_driver = {
.driver = {
.name = "twl-pwm",
.of_match_table = of_match_ptr(twl_pwm_of_match),
},
.probe = twl_pwm_probe,
.remove = twl_pwm_remove,
};
module_platform_driver(twl_pwm_driver);
MODULE_AUTHOR("Peter Ujfalusi <peter.ujfalusi@ti.com>");
MODULE_DESCRIPTION("PWM driver for TWL4030 and TWL6030");
MODULE_ALIAS("platform:twl-pwm");
MODULE_LICENSE("GPL");
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