[PATCH v5 07/13] pwm: add support for sl28cpld PWM controller

[Michael Walle <michael@walle.cc>]

Add support for the PWM controller of the sl28cpld board management
controller. This is part of a multi-function device driver.

The controller has one PWM channel and can just generate four distinct
frequencies.

Signed-off-by: Michael Walle <michael@walle.cc>
---
Changes since v4:
 - update copyright year
 - remove #include <linux/of_device.h>, suggested by Andy.
 - make the pwm mode table look nicer, suggested by Lee.
 - use dev_get_drvdata(chip->dev) instead of container_of(), suggested by
   Lee.
 - use whole sentence in comments, suggested by Lee.
 - renamed the local "struct sl28cpld_pwm" variable to "priv" everywhere,
   suggested by Lee.
 - use pwm_{get,set}_relative_duty_cycle(), suggested by Andy.
 - make the comment about the 250Hz hardware limitation clearer
 - don't use "if (ret < 0)", but only "if (ret)", suggested by Andy.
 - don't use KBUID_MODNAME
 - remove comma in terminator line of the compatible strings list
 - remove the platform device table

Changes since v3:
 - see cover letter

 drivers/pwm/Kconfig        |  10 ++
 drivers/pwm/Makefile       |   1 +
 drivers/pwm/pwm-sl28cpld.c | 187 +++++++++++++++++++++++++++++++++++++
 3 files changed, 198 insertions(+)
 create mode 100644 drivers/pwm/pwm-sl28cpld.c

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 7dbcf6973d33..a0d50d70c3b9 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -428,6 +428,16 @@ config PWM_SIFIVE
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-sifive.
 
+config PWM_SL28CPLD
+	tristate "Kontron sl28cpld PWM support"
+	select MFD_SIMPLE_MFD_I2C
+	help
+	  Generic PWM framework driver for board management controller
+	  found on the Kontron sl28 CPLD.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-sl28cpld.
+
 config PWM_SPEAR
 	tristate "STMicroelectronics SPEAr PWM support"
 	depends on PLAT_SPEAR || COMPILE_TEST
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 2c2ba0a03557..cbdcd55d69ee 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -40,6 +40,7 @@ obj-$(CONFIG_PWM_RENESAS_TPU)	+= pwm-renesas-tpu.o
 obj-$(CONFIG_PWM_ROCKCHIP)	+= pwm-rockchip.o
 obj-$(CONFIG_PWM_SAMSUNG)	+= pwm-samsung.o
 obj-$(CONFIG_PWM_SIFIVE)	+= pwm-sifive.o
+obj-$(CONFIG_PWM_SL28CPLD)	+= pwm-sl28cpld.o
 obj-$(CONFIG_PWM_SPEAR)		+= pwm-spear.o
 obj-$(CONFIG_PWM_SPRD)		+= pwm-sprd.o
 obj-$(CONFIG_PWM_STI)		+= pwm-sti.o
diff --git a/drivers/pwm/pwm-sl28cpld.c b/drivers/pwm/pwm-sl28cpld.c
new file mode 100644
index 000000000000..8ee286b605bf
--- /dev/null
+++ b/drivers/pwm/pwm-sl28cpld.c
@@ -0,0 +1,187 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * sl28cpld PWM driver
+ *
+ * Copyright 2020 Kontron Europe GmbH
+ */
+
+#include <linux/bitfield.h>
+#include <linux/kernel.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/regmap.h>
+
+/*
+ * PWM timer block registers.
+ */
+#define PWM_CTRL		0x00
+#define   PWM_ENABLE		BIT(7)
+#define   PWM_MODE_250HZ	0
+#define   PWM_MODE_500HZ	1
+#define   PWM_MODE_1KHZ		2
+#define   PWM_MODE_2KHZ		3
+#define   PWM_MODE_MASK		GENMASK(1, 0)
+#define PWM_CYCLE		0x01
+#define   PWM_CYCLE_MAX		0x7f
+
+struct sl28cpld_pwm {
+	struct pwm_chip pwm_chip;
+	struct regmap *regmap;
+	u32 offset;
+};
+
+struct sl28cpld_pwm_periods {
+	u8 ctrl;
+	unsigned long duty_cycle;
+};
+
+struct sl28cpld_pwm_config {
+	unsigned long period_ns;
+	u8 max_duty_cycle;
+};
+
+static struct sl28cpld_pwm_config sl28cpld_pwm_config[] = {
+	[PWM_MODE_250HZ] = { .period_ns = 4000000, .max_duty_cycle = 0x80 },
+	[PWM_MODE_500HZ] = { .period_ns = 2000000, .max_duty_cycle = 0x40 },
+	[PWM_MODE_1KHZ]  = { .period_ns = 1000000, .max_duty_cycle = 0x20 },
+	[PWM_MODE_2KHZ]  = { .period_ns =  500000, .max_duty_cycle = 0x10 },
+};
+
+static void sl28cpld_pwm_get_state(struct pwm_chip *chip,
+				   struct pwm_device *pwm,
+				   struct pwm_state *state)
+{
+	struct sl28cpld_pwm *priv = dev_get_drvdata(chip->dev);
+	static struct sl28cpld_pwm_config *config;
+	unsigned int reg;
+	unsigned int mode;
+
+	regmap_read(priv->regmap, priv->offset + PWM_CTRL, &reg);
+
+	state->enabled = reg & PWM_ENABLE;
+
+	mode = FIELD_GET(PWM_MODE_MASK, reg);
+	config = &sl28cpld_pwm_config[mode];
+	state->period = config->period_ns;
+
+	regmap_read(priv->regmap, priv->offset + PWM_CYCLE, &reg);
+	pwm_set_relative_duty_cycle(state, reg, config->max_duty_cycle);
+}
+
+static int sl28cpld_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			      const struct pwm_state *state)
+{
+	struct sl28cpld_pwm *priv = dev_get_drvdata(chip->dev);
+	struct sl28cpld_pwm_config *config;
+	unsigned int cycle;
+	int ret;
+	int mode;
+	u8 ctrl;
+
+	/* Get the configuration by comparing the period */
+	for (mode = 0; mode < ARRAY_SIZE(sl28cpld_pwm_config); mode++) {
+		config = &sl28cpld_pwm_config[mode];
+		if (state->period == config->period_ns)
+			break;
+	}
+
+	if (mode == ARRAY_SIZE(sl28cpld_pwm_config))
+		return -EINVAL;
+
+	ctrl = FIELD_PREP(PWM_MODE_MASK, mode);
+	if (state->enabled)
+		ctrl |= PWM_ENABLE;
+
+	cycle = pwm_get_relative_duty_cycle(state, config->max_duty_cycle);
+
+	/*
+	 * The hardware doesn't allow to set max_duty_cycle if the
+	 * 250Hz mode is enabled, thus we have to trap that here.
+	 * But because a 100% duty cycle is equal on all modes, i.e.
+	 * it is just a "all-high" output, we trap any case with a
+	 * 100% duty cycle and use the 500Hz mode.
+	 */
+	if (cycle == config->max_duty_cycle) {
+		ctrl &= ~PWM_MODE_MASK;
+		ctrl |= FIELD_PREP(PWM_MODE_MASK, PWM_MODE_500HZ);
+		cycle = PWM_CYCLE_MAX;
+	}
+
+	ret = regmap_write(priv->regmap, priv->offset + PWM_CTRL, ctrl);
+	if (ret)
+		return ret;
+
+	return regmap_write(priv->regmap, priv->offset + PWM_CYCLE, (u8)cycle);
+}
+
+static const struct pwm_ops sl28cpld_pwm_ops = {
+	.apply = sl28cpld_pwm_apply,
+	.get_state = sl28cpld_pwm_get_state,
+	.owner = THIS_MODULE,
+};
+
+static int sl28cpld_pwm_probe(struct platform_device *pdev)
+{
+	struct sl28cpld_pwm *priv;
+	struct pwm_chip *chip;
+	int ret;
+
+	if (!pdev->dev.parent)
+		return -ENODEV;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->regmap = dev_get_regmap(pdev->dev.parent, NULL);
+	if (!priv->regmap)
+		return -ENODEV;
+
+	ret = device_property_read_u32(&pdev->dev, "reg", &priv->offset);
+	if (ret)
+		return -EINVAL;
+
+	/* Initialize the pwm_chip structure */
+	chip = &priv->pwm_chip;
+	chip->dev = &pdev->dev;
+	chip->ops = &sl28cpld_pwm_ops;
+	chip->base = -1;
+	chip->npwm = 1;
+
+	ret = pwmchip_add(&priv->pwm_chip);
+	if (ret)
+		return ret;
+
+	platform_set_drvdata(pdev, priv);
+
+	return 0;
+}
+
+static int sl28cpld_pwm_remove(struct platform_device *pdev)
+{
+	struct sl28cpld_pwm *priv = platform_get_drvdata(pdev);
+
+	return pwmchip_remove(&priv->pwm_chip);
+}
+
+static const struct of_device_id sl28cpld_pwm_of_match[] = {
+	{ .compatible = "kontron,sl28cpld-pwm" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, sl28cpld_pwm_of_match);
+
+static struct platform_driver sl28cpld_pwm_driver = {
+	.probe = sl28cpld_pwm_probe,
+	.remove	= sl28cpld_pwm_remove,
+	.driver = {
+		.name = "sl28cpld-pwm",
+		.of_match_table = sl28cpld_pwm_of_match,
+	},
+};
+module_platform_driver(sl28cpld_pwm_driver);
+
+MODULE_DESCRIPTION("sl28cpld PWM Driver");
+MODULE_AUTHOR("Michael Walle <michael@walle.cc>");
+MODULE_LICENSE("GPL");
-- 
2.20.1