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>
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index d298ebd..59124eb 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -372,6 +372,13 @@
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
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index a196d79..98ae3cb 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -35,6 +35,7 @@
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
diff --git a/drivers/pwm/pwm-stmpe.c b/drivers/pwm/pwm-stmpe.c
new file mode 100644
index 0000000..e464582
--- /dev/null
+++ b/drivers/pwm/pwm-stmpe.c
@@ -0,0 +1,319 @@
+/*
+ * 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);