pwm: Add driver for STM32 plaftorm

This driver adds support for PWM driver on STM32 platform.
The SoC have multiple instances of the hardware IP and each
of them could have small differences: number of channels,
complementary output, auto reload register size...

version 9:
- fix commit message header
- remove one space MODULE_ALIAS

version 8:
- fix comments done by Thierry on version 7

version 6:
- change st,breakinput parameter to make it usuable for stm32f7 too.

version 4:
- detect at probe time hardware capabilities
- fix comments done on v2 and v3
- use PWM atomic ops

version 2:
- only keep one comptatible
- use DT parameters to discover hardware block configuration

Signed-off-by: Benjamin Gaignard <[e-mail]>
Acked-by: Thierry Reding <[e-mail]>
Signed-off-by: Lee Jones <[e-mail]>

drivers/pwm/Kconfig

···
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-sti.
 
+config PWM_STM32
+	tristate "STMicroelectronics STM32 PWM"
+	depends on MFD_STM32_TIMERS || COMPILE_TEST
+	help
+	  Generic PWM framework driver for STM32 SoCs.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-stm32.
+
 config PWM_STMPE
 	bool "STMPE expander PWM export"
 	depends on MFD_STMPE

drivers/pwm/Makefile

···
 obj-$(CONFIG_PWM_SAMSUNG)	+= pwm-samsung.o
 obj-$(CONFIG_PWM_SPEAR)		+= pwm-spear.o
 obj-$(CONFIG_PWM_STI)		+= pwm-sti.o
+obj-$(CONFIG_PWM_STM32)		+= pwm-stm32.o
 obj-$(CONFIG_PWM_STMPE)		+= pwm-stmpe.o
 obj-$(CONFIG_PWM_SUN4I)		+= pwm-sun4i.o
 obj-$(CONFIG_PWM_TEGRA)		+= pwm-tegra.o

drivers/pwm/pwm-stm32.c

···
+/*
+ * Copyright (C) STMicroelectronics 2016
+ *
+ * Author: Gerald Baeza <[e-mail]>
+ *
+ * License terms: GNU General Public License (GPL), version 2
+ *
+ * Inspired by timer-stm32.c from Maxime Coquelin
+ *             pwm-atmel.c from Bo Shen
+ */
+
+#include <linux/mfd/stm32-timers.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+
+#define CCMR_CHANNEL_SHIFT 8
+#define CCMR_CHANNEL_MASK  0xFF
+#define MAX_BREAKINPUT 2
+
+struct stm32_pwm {
+	struct pwm_chip chip;
+	struct device *dev;
+	struct clk *clk;
+	struct regmap *regmap;
+	u32 max_arr;
+	bool have_complementary_output;
+};
+
+struct stm32_breakinput {
+	u32 index;
+	u32 level;
+	u32 filter;
+};
+
+static inline struct stm32_pwm *to_stm32_pwm_dev(struct pwm_chip *chip)
+{
+	return container_of(chip, struct stm32_pwm, chip);
+}
+
+static u32 active_channels(struct stm32_pwm *dev)
+{
+	u32 ccer;
+
+	regmap_read(dev->regmap, TIM_CCER, &ccer);
+
+	return ccer & TIM_CCER_CCXE;
+}
+
+static int write_ccrx(struct stm32_pwm *dev, int ch, u32 value)
+{
+	switch (ch) {
+	case 0:
+		return regmap_write(dev->regmap, TIM_CCR1, value);
+	case 1:
+		return regmap_write(dev->regmap, TIM_CCR2, value);
+	case 2:
+		return regmap_write(dev->regmap, TIM_CCR3, value);
+	case 3:
+		return regmap_write(dev->regmap, TIM_CCR4, value);
+	}
+	return -EINVAL;
+}
+
+static int stm32_pwm_config(struct stm32_pwm *priv, int ch,
+			    int duty_ns, int period_ns)
+{
+	unsigned long long prd, div, dty;
+	unsigned int prescaler = 0;
+	u32 ccmr, mask, shift;
+
+	/* Period and prescaler values depends on clock rate */
+	div = (unsigned long long)clk_get_rate(priv->clk) * period_ns;
+
+	do_div(div, NSEC_PER_SEC);
+	prd = div;
+
+	while (div > priv->max_arr) {
+		prescaler++;
+		div = prd;
+		do_div(div, prescaler + 1);
+	}
+
+	prd = div;
+
+	if (prescaler > MAX_TIM_PSC)
+		return -EINVAL;
+
+	/*
+	 * All channels share the same prescaler and counter so when two
+	 * channels are active at the same time we can't change them
+	 */
+	if (active_channels(priv) & ~(1 << ch * 4)) {
+		u32 psc, arr;
+
+		regmap_read(priv->regmap, TIM_PSC, &psc);
+		regmap_read(priv->regmap, TIM_ARR, &arr);
+
+		if ((psc != prescaler) || (arr != prd - 1))
+			return -EBUSY;
+	}
+
+	regmap_write(priv->regmap, TIM_PSC, prescaler);
+	regmap_write(priv->regmap, TIM_ARR, prd - 1);
+	regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_ARPE, TIM_CR1_ARPE);
+
+	/* Calculate the duty cycles */
+	dty = prd * duty_ns;
+	do_div(dty, period_ns);
+
+	write_ccrx(priv, ch, dty);
+
+	/* Configure output mode */
+	shift = (ch & 0x1) * CCMR_CHANNEL_SHIFT;
+	ccmr = (TIM_CCMR_PE | TIM_CCMR_M1) << shift;
+	mask = CCMR_CHANNEL_MASK << shift;
+
+	if (ch < 2)
+		regmap_update_bits(priv->regmap, TIM_CCMR1, mask, ccmr);
+	else
+		regmap_update_bits(priv->regmap, TIM_CCMR2, mask, ccmr);
+
+	regmap_update_bits(priv->regmap, TIM_BDTR,
+			   TIM_BDTR_MOE | TIM_BDTR_AOE,
+			   TIM_BDTR_MOE | TIM_BDTR_AOE);
+
+	return 0;
+}
+
+static int stm32_pwm_set_polarity(struct stm32_pwm *priv, int ch,
+				  enum pwm_polarity polarity)
+{
+	u32 mask;
+
+	mask = TIM_CCER_CC1P << (ch * 4);
+	if (priv->have_complementary_output)
+		mask |= TIM_CCER_CC1NP << (ch * 4);
+
+	regmap_update_bits(priv->regmap, TIM_CCER, mask,
+			   polarity == PWM_POLARITY_NORMAL ? 0 : mask);
+
+	return 0;
+}
+
+static int stm32_pwm_enable(struct stm32_pwm *priv, int ch)
+{
+	u32 mask;
+	int ret;
+
+	ret = clk_enable(priv->clk);
+	if (ret)
+		return ret;
+
+	/* Enable channel */
+	mask = TIM_CCER_CC1E << (ch * 4);
+	if (priv->have_complementary_output)
+		mask |= TIM_CCER_CC1NE << (ch * 4);
+
+	regmap_update_bits(priv->regmap, TIM_CCER, mask, mask);
+
+	/* Make sure that registers are updated */
+	regmap_update_bits(priv->regmap, TIM_EGR, TIM_EGR_UG, TIM_EGR_UG);
+
+	/* Enable controller */
+	regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_CEN, TIM_CR1_CEN);
+
+	return 0;
+}
+
+static void stm32_pwm_disable(struct stm32_pwm *priv, int ch)
+{
+	u32 mask;
+
+	/* Disable channel */
+	mask = TIM_CCER_CC1E << (ch * 4);
+	if (priv->have_complementary_output)
+		mask |= TIM_CCER_CC1NE << (ch * 4);
+
+	regmap_update_bits(priv->regmap, TIM_CCER, mask, 0);
+
+	/* When all channels are disabled, we can disable the controller */
+	if (!active_channels(priv))
+		regmap_update_bits(priv->regmap, TIM_CR1, TIM_CR1_CEN, 0);
+
+	clk_disable(priv->clk);
+}
+
+static int stm32_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			   struct pwm_state *state)
+{
+	bool enabled;
+	struct stm32_pwm *priv = to_stm32_pwm_dev(chip);
+	int ret;
+
+	enabled = pwm->state.enabled;
+
+	if (enabled && !state->enabled) {
+		stm32_pwm_disable(priv, pwm->hwpwm);
+		return 0;
+	}
+
+	if (state->polarity != pwm->state.polarity)
+		stm32_pwm_set_polarity(priv, pwm->hwpwm, state->polarity);
+
+	ret = stm32_pwm_config(priv, pwm->hwpwm,
+			       state->duty_cycle, state->period);
+	if (ret)
+		return ret;
+
+	if (!enabled && state->enabled)
+		ret = stm32_pwm_enable(priv, pwm->hwpwm);
+
+	return ret;
+}
+
+static const struct pwm_ops stm32pwm_ops = {
+	.owner = THIS_MODULE,
+	.apply = stm32_pwm_apply,
+};
+
+static int stm32_pwm_set_breakinput(struct stm32_pwm *priv,
+				    int index, int level, int filter)
+{
+	u32 bke = (index == 0) ? TIM_BDTR_BKE : TIM_BDTR_BK2E;
+	int shift = (index == 0) ? TIM_BDTR_BKF_SHIFT : TIM_BDTR_BK2F_SHIFT;
+	u32 mask = (index == 0) ? TIM_BDTR_BKE | TIM_BDTR_BKP | TIM_BDTR_BKF
+				: TIM_BDTR_BK2E | TIM_BDTR_BK2P | TIM_BDTR_BK2F;
+	u32 bdtr = bke;
+
+	/*
+	 * The both bits could be set since only one will be wrote
+	 * due to mask value.
+	 */
+	if (level)
+		bdtr |= TIM_BDTR_BKP | TIM_BDTR_BK2P;
+
+	bdtr |= (filter & TIM_BDTR_BKF_MASK) << shift;
+
+	regmap_update_bits(priv->regmap, TIM_BDTR, mask, bdtr);
+
+	regmap_read(priv->regmap, TIM_BDTR, &bdtr);
+
+	return (bdtr & bke) ? 0 : -EINVAL;
+}
+
+static int stm32_pwm_apply_breakinputs(struct stm32_pwm *priv,
+				       struct device_node *np)
+{
+	struct stm32_breakinput breakinput[MAX_BREAKINPUT];
+	int nb, ret, i, array_size;
+
+	nb = of_property_count_elems_of_size(np, "st,breakinput",
+					     sizeof(struct stm32_breakinput));
+
+	/*
+	 * Because "st,breakinput" parameter is optional do not make probe
+	 * failed if it doesn't exist.
+	 */
+	if (nb <= 0)
+		return 0;
+
+	if (nb > MAX_BREAKINPUT)
+		return -EINVAL;
+
+	array_size = nb * sizeof(struct stm32_breakinput) / sizeof(u32);
+	ret = of_property_read_u32_array(np, "st,breakinput",
+					 (u32 *)breakinput, array_size);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < nb && !ret; i++) {
+		ret = stm32_pwm_set_breakinput(priv,
+					       breakinput[i].index,
+					       breakinput[i].level,
+					       breakinput[i].filter);
+	}
+
+	return ret;
+}
+
+static void stm32_pwm_detect_complementary(struct stm32_pwm *priv)
+{
+	u32 ccer;
+
+	/*
+	 * If complementary bit doesn't exist writing 1 will have no
+	 * effect so we can detect it.
+	 */
+	regmap_update_bits(priv->regmap,
+			   TIM_CCER, TIM_CCER_CC1NE, TIM_CCER_CC1NE);
+	regmap_read(priv->regmap, TIM_CCER, &ccer);
+	regmap_update_bits(priv->regmap, TIM_CCER, TIM_CCER_CC1NE, 0);
+
+	priv->have_complementary_output = (ccer != 0);
+}
+
+static int stm32_pwm_detect_channels(struct stm32_pwm *priv)
+{
+	u32 ccer;
+	int npwm = 0;
+
+	/*
+	 * If channels enable bits don't exist writing 1 will have no
+	 * effect so we can detect and count them.
+	 */
+	regmap_update_bits(priv->regmap,
+			   TIM_CCER, TIM_CCER_CCXE, TIM_CCER_CCXE);
+	regmap_read(priv->regmap, TIM_CCER, &ccer);
+	regmap_update_bits(priv->regmap, TIM_CCER, TIM_CCER_CCXE, 0);
+
+	if (ccer & TIM_CCER_CC1E)
+		npwm++;
+
+	if (ccer & TIM_CCER_CC2E)
+		npwm++;
+
+	if (ccer & TIM_CCER_CC3E)
+		npwm++;
+
+	if (ccer & TIM_CCER_CC4E)
+		npwm++;
+
+	return npwm;
+}
+
+static int stm32_pwm_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	struct stm32_timers *ddata = dev_get_drvdata(pdev->dev.parent);
+	struct stm32_pwm *priv;
+	int ret;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->regmap = ddata->regmap;
+	priv->clk = ddata->clk;
+	priv->max_arr = ddata->max_arr;
+
+	if (!priv->regmap || !priv->clk)
+		return -EINVAL;
+
+	ret = stm32_pwm_apply_breakinputs(priv, np);
+	if (ret)
+		return ret;
+
+	stm32_pwm_detect_complementary(priv);
+
+	priv->chip.base = -1;
+	priv->chip.dev = dev;
+	priv->chip.ops = &stm32pwm_ops;
+	priv->chip.npwm = stm32_pwm_detect_channels(priv);
+
+	ret = pwmchip_add(&priv->chip);
+	if (ret < 0)
+		return ret;
+
+	platform_set_drvdata(pdev, priv);
+
+	return 0;
+}
+
+static int stm32_pwm_remove(struct platform_device *pdev)
+{
+	struct stm32_pwm *priv = platform_get_drvdata(pdev);
+	unsigned int i;
+
+	for (i = 0; i < priv->chip.npwm; i++)
+		pwm_disable(&priv->chip.pwms[i]);
+
+	pwmchip_remove(&priv->chip);
+
+	return 0;
+}
+
+static const struct of_device_id stm32_pwm_of_match[] = {
+	{ .compatible = "st,stm32-pwm",	},
+	{ /* end node */ },
+};
+MODULE_DEVICE_TABLE(of, stm32_pwm_of_match);
+
+static struct platform_driver stm32_pwm_driver = {
+	.probe	= stm32_pwm_probe,
+	.remove	= stm32_pwm_remove,
+	.driver	= {
+		.name = "stm32-pwm",
+		.of_match_table = stm32_pwm_of_match,
+	},
+};
+module_platform_driver(stm32_pwm_driver);
+
+MODULE_ALIAS("platform:stm32-pwm");
+MODULE_DESCRIPTION("STMicroelectronics STM32 PWM driver");
+MODULE_LICENSE("GPL v2");