[PATCH v4 4/7] PWM: add PWM driver for STM32 plaftorm

[Benjamin Gaignard]

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 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 <benjamin.gaignard@xxxxxx>
---
 drivers/pwm/Kconfig     |  11 ++
 drivers/pwm/Makefile    |   1 +
 drivers/pwm/pwm-stm32.c | 363 ++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 375 insertions(+)
 create mode 100644 drivers/pwm/pwm-stm32.c

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index bf01288..95c9f04 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -388,6 +388,17 @@ config PWM_STI
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-sti.
 
+config PWM_STM32
+	bool "STMicroelectronics STM32 PWM"
+	depends on ARCH_STM32 || COMPILE_TEST
+	depends on OF
+	depends on MFD_STM32_GP_TIMER
+	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
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 1194c54..5aa9308 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -37,6 +37,7 @@ 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-$(CONFIG_PWM_STM32)		+= pwm-stm32.o
 obj-$(CONFIG_PWM_STMPE)		+= pwm-stmpe.o
 obj-$(CONFIG_PWM_SUN4I)		+= pwm-sun4i.o
 obj-$(CONFIG_PWM_TEGRA)		+= pwm-tegra.o
diff --git a/drivers/pwm/pwm-stm32.c b/drivers/pwm/pwm-stm32.c
new file mode 100644
index 0000000..319fd77
--- /dev/null
+++ b/drivers/pwm/pwm-stm32.c
@@ -0,0 +1,363 @@
+/*
+ * Copyright (C) STMicroelectronics 2016
+ *
+ * Author: Gerald Baeza <gerald.baeza@xxxxxx>
+ * 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/module.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/of.h>
+
+#include <linux/mfd/stm32-gptimer.h>
+
+#define CCMR_CHANNEL_SHIFT 8
+#define CCMR_CHANNEL_MASK  0xFF
+
+struct stm32_pwm {
+	struct pwm_chip chip;
+	struct device *dev;
+	struct clk *clk;
+	struct regmap *regmap;
+	unsigned int caps;
+	unsigned int npwm;
+	u32 breakinput_polarity;
+	u32 max_arr;
+	bool have_complementary_output;
+	bool have_breakinput;
+	bool use_breakinput;
+};
+
+#define to_stm32_pwm_dev(x) 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, struct pwm_device *pwm,
+		      u32 value)
+{
+	switch (pwm->hwpwm) {
+	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 pwm_chip *chip, struct pwm_device *pwm,
+			    int duty_ns, int period_ns)
+{
+	struct stm32_pwm *priv = to_stm32_pwm_dev(chip);
+	unsigned long long prd, div, dty;
+	unsigned int prescaler = 0;
+	u32 ccmr, mask, shift, bdtr;
+
+	/* 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) {
+		dev_err(chip->dev, "prescaler exceeds the maximum value\n");
+		return -EINVAL;
+	}
+
+	/*
+	 * All channels share the same prescaler and counter so when two
+	 * channels are active at the same we can't change them
+	 */
+	if (active_channels(priv) & ~(1 << pwm->hwpwm * 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, pwm, dty);
+
+	/* Configure output mode */
+	shift = (pwm->hwpwm & 0x1) * CCMR_CHANNEL_SHIFT;
+	ccmr = (TIM_CCMR_PE | TIM_CCMR_M1) << shift;
+	mask = CCMR_CHANNEL_MASK << shift;
+
+	if (pwm->hwpwm < 2)
+		regmap_update_bits(priv->regmap, TIM_CCMR1, mask, ccmr);
+	else
+		regmap_update_bits(priv->regmap, TIM_CCMR2, mask, ccmr);
+
+	if (!priv->have_breakinput)
+		return 0;
+
+	bdtr = TIM_BDTR_MOE | TIM_BDTR_AOE;
+
+	if (priv->use_breakinput)
+		bdtr |= TIM_BDTR_BKE;
+
+	if (priv->breakinput_polarity)
+		bdtr |= TIM_BDTR_BKP;
+
+	regmap_update_bits(priv->regmap, TIM_BDTR,
+			   TIM_BDTR_MOE | TIM_BDTR_AOE |
+			   TIM_BDTR_BKP | TIM_BDTR_BKE,
+			   bdtr);
+
+	return 0;
+}
+
+static int stm32_pwm_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
+				  enum pwm_polarity polarity)
+{
+	u32 mask;
+	struct stm32_pwm *priv = to_stm32_pwm_dev(chip);
+
+	mask = TIM_CCER_CC1P << (pwm->hwpwm * 4);
+	if (priv->have_complementary_output)
+		mask |= TIM_CCER_CC1NP << (pwm->hwpwm * 4);
+
+	regmap_update_bits(priv->regmap, TIM_CCER, mask,
+			   polarity == PWM_POLARITY_NORMAL ? 0 : mask);
+
+	return 0;
+}
+
+static int stm32_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	u32 mask;
+	struct stm32_pwm *priv = to_stm32_pwm_dev(chip);
+
+	clk_enable(priv->clk);
+
+	/* Enable channel */
+	mask = TIM_CCER_CC1E << (pwm->hwpwm * 4);
+	if (priv->have_complementary_output)
+		mask |= TIM_CCER_CC1NE << (pwm->hwpwm * 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 pwm_chip *chip, struct pwm_device *pwm)
+{
+	u32 mask;
+	struct stm32_pwm *priv = to_stm32_pwm_dev(chip);
+
+	/* Disable channel */
+	mask = TIM_CCER_CC1E << (pwm->hwpwm * 4);
+	if (priv->have_complementary_output)
+		mask |= TIM_CCER_CC1NE << (pwm->hwpwm * 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)
+{
+	struct pwm_state curstate;
+	bool enabled;
+	int ret;
+
+	pwm_get_state(pwm, &curstate);
+	enabled = curstate.enabled;
+
+	if (enabled && !state->enabled) {
+		stm32_pwm_disable(chip, pwm);
+		return 0;
+	}
+
+	if (state->polarity != curstate.polarity && enabled)
+		stm32_pwm_set_polarity(chip, pwm, state->polarity);
+
+	ret = stm32_pwm_config(chip, pwm, state->duty_cycle, state->period);
+	if (ret)
+		return ret;
+
+	if (!enabled && state->enabled)
+		ret = stm32_pwm_enable(chip, pwm);
+
+	return ret;
+}
+
+static const struct pwm_ops stm32pwm_ops = {
+	.owner = THIS_MODULE,
+	.apply = stm32_pwm_apply,
+};
+
+static bool stm32_pwm_detect_breakinput(struct regmap *regmap)
+{
+	u32 bdtr;
+
+	/*
+	 * If breakinput enable bit doesn't exist writing 1 will have no
+	 * effect so we can detect it.
+	 */
+	regmap_update_bits(regmap, TIM_BDTR, TIM_BDTR_BKE, TIM_BDTR_BKE);
+	regmap_read(regmap, TIM_BDTR, &bdtr);
+	regmap_update_bits(regmap, TIM_BDTR, TIM_BDTR_BKE, 0);
+
+	return (bdtr != 0);
+}
+
+static bool stm32_pwm_detect_complementary(struct regmap *regmap)
+{
+	u32 ccer;
+
+	/*
+	 * If complementary bit doesn't exist writing 1 will have no
+	 * effect so we can detect it.
+	 */
+	regmap_update_bits(regmap, TIM_CCER, TIM_CCER_CC1NE, TIM_CCER_CC1NE);
+	regmap_read(regmap, TIM_CCER, &ccer);
+	regmap_update_bits(regmap, TIM_CCER, TIM_CCER_CCXE, 0);
+
+	return (ccer != 0);
+}
+
+static int stm32_pwm_detect_channels(struct regmap *regmap)
+{
+	int channels = 0;
+	u32 ccer;
+
+	/*
+	 * If channels enable bits don't exist writing 1 will have no
+	 * effect so we can detect and count them.
+	 */
+	regmap_update_bits(regmap, TIM_CCER, TIM_CCER_CCXE, TIM_CCER_CCXE);
+	regmap_read(regmap, TIM_CCER, &ccer);
+	regmap_update_bits(regmap, TIM_CCER, TIM_CCER_CCXE, 0);
+
+	if (ccer & TIM_CCER_CC1E)
+		channels++;
+
+	if (ccer & TIM_CCER_CC2E)
+		channels++;
+
+	if (ccer & TIM_CCER_CC3E)
+		channels++;
+
+	if (ccer & TIM_CCER_CC4E)
+		channels++;
+
+	return channels;
+}
+
+static int stm32_pwm_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	struct stm32_gptimer *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;
+
+	priv->have_breakinput = stm32_pwm_detect_breakinput(priv->regmap);
+	priv->have_complementary_output =
+		stm32_pwm_detect_complementary(priv->regmap);
+	priv->npwm = stm32_pwm_detect_channels(priv->regmap);
+
+	if (!of_property_read_u32(np, "st,breakinput-polarity",
+				  &priv->breakinput_polarity))
+		priv->use_breakinput = true;
+
+	priv->chip.base = -1;
+	priv->chip.dev = dev;
+	priv->chip.ops = &stm32pwm_ops;
+	priv->chip.npwm = priv->npwm;
+
+	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->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",	}
+};
+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");
-- 
1.9.1