[PATCH v3 2/2] Add PWM fan controller driver for LGM SoC

[Rahul Tanwar]

Intel Lightning Mountain(LGM) SoC contains a PWM fan controller.
This PWM controller does not have any other consumer, it is a
dedicated PWM controller for fan attached to the system. Add
driver for this PWM fan controller.

Signed-off-by: Rahul Tanwar <rahul.tanwar@xxxxxxxxxxxxxxx>
---
 drivers/pwm/Kconfig         |   9 ++
 drivers/pwm/Makefile        |   1 +
 drivers/pwm/pwm-intel-lgm.c | 265 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 275 insertions(+)
 create mode 100644 drivers/pwm/pwm-intel-lgm.c

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index cb8d739067d2..a3303e22d5fa 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -232,6 +232,15 @@ config PWM_IMX_TPM
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-imx-tpm.
 
+config PWM_INTEL_LGM
+	tristate "Intel LGM PWM support"
+	depends on X86 || COMPILE_TEST
+	help
+	  Generic PWM fan controller driver for LGM SoC.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-intel-lgm.
+
 config PWM_IQS620A
 	tristate "Azoteq IQS620A PWM support"
 	depends on MFD_IQS62X || COMPILE_TEST
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index a59c710e98c7..db154a6b4f51 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -20,6 +20,7 @@ obj-$(CONFIG_PWM_IMG)		+= pwm-img.o
 obj-$(CONFIG_PWM_IMX1)		+= pwm-imx1.o
 obj-$(CONFIG_PWM_IMX27)		+= pwm-imx27.o
 obj-$(CONFIG_PWM_IMX_TPM)	+= pwm-imx-tpm.o
+obj-$(CONFIG_PWM_INTEL_LGM)	+= pwm-intel-lgm.o
 obj-$(CONFIG_PWM_IQS620A)	+= pwm-iqs620a.o
 obj-$(CONFIG_PWM_JZ4740)	+= pwm-jz4740.o
 obj-$(CONFIG_PWM_LP3943)	+= pwm-lp3943.o
diff --git a/drivers/pwm/pwm-intel-lgm.c b/drivers/pwm/pwm-intel-lgm.c
new file mode 100644
index 000000000000..661fa7d9145d
--- /dev/null
+++ b/drivers/pwm/pwm-intel-lgm.c
@@ -0,0 +1,265 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020 Intel Corporation.
+ *
+ * Notes & Limitations:
+ * - The hardware supports fixed period which is dependent on 2/3 or 4
+ *   wire fan mode.
+ * - Supports normal polarity. Does not support changing polarity.
+ * - When PWM is disabled, output of PWM will become 0(inactive). It doesn't
+ *   keep track of running period.
+ * - When duty cycle is changed, PWM output may be a mix of previous setting
+ *   and new setting for the first period. From second period, the output is
+ *   based on new setting.
+ * - Supports 100% duty cycle.
+ * - It is a dedicated PWM fan controller. There are no other consumers for
+ *   this PWM controller.
+ */
+#include <linux/bitfield.h>
+#include <linux/clk.h>
+#include <linux/module.h>
+#include <linux/of_device.h>
+#include <linux/pwm.h>
+#include <linux/regmap.h>
+#include <linux/reset.h>
+
+#define PWM_FAN_CON0		0x0
+#define PWM_FAN_EN_EN		BIT(0)
+#define PWM_FAN_EN_DIS		0x0
+#define PWM_FAN_EN_MSK		BIT(0)
+#define PWM_FAN_MODE_2WIRE	0x0
+#define PWM_FAN_MODE_4WIRE	0x1
+#define PWM_FAN_MODE_MSK	BIT(1)
+#define PWM_FAN_DC_MSK		GENMASK(23, 16)
+
+#define PWM_FAN_CON1		0x4
+#define PWM_FAN_MAX_RPM_MSK	GENMASK(15, 0)
+
+#define MAX_RPM			(BIT(16) - 1)
+#define DFAULT_RPM		4000
+#define MAX_DUTY_CYCLE		(BIT(8) - 1)
+
+#define DC_BITS			8
+
+#define PERIOD_2WIRE_NSECS	40000000
+#define PERIOD_4WIRE_NSECS	40000
+
+#define LGM_PWM_DIV_ROUND_DOWN(n, d) (((n) + ((d) / 2) - 1) / (d))
+
+struct lgm_pwm_chip {
+	struct pwm_chip chip;
+	struct regmap *regmap;
+	struct clk *clk;
+	struct reset_control *rst;
+	u32 period;
+};
+
+static inline struct lgm_pwm_chip *to_lgm_pwm_chip(struct pwm_chip *chip)
+{
+	return container_of(chip, struct lgm_pwm_chip, chip);
+}
+
+static int lgm_pwm_enable(struct pwm_chip *chip, bool enable)
+{
+	struct lgm_pwm_chip *pc = to_lgm_pwm_chip(chip);
+	struct regmap *regmap = pc->regmap;
+
+	if (enable)
+		regmap_update_bits(regmap, PWM_FAN_CON0,
+				   PWM_FAN_EN_MSK, PWM_FAN_EN_EN);
+	else
+		regmap_update_bits(regmap, PWM_FAN_CON0,
+			   	   PWM_FAN_EN_MSK, PWM_FAN_EN_DIS);
+
+	return 0;
+}
+
+static int lgm_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			 const struct pwm_state *state)
+{
+	struct lgm_pwm_chip *pc = to_lgm_pwm_chip(chip);
+	u32 duty_cycle, val;
+	unsigned int period;
+
+	period = min_t(unsigned int, state->period, pc->period);
+
+	if (state->polarity != PWM_POLARITY_NORMAL ||
+	    period < pc->period)
+		return -EINVAL;
+
+	duty_cycle = min_t(u32, state->duty_cycle, period);
+
+	/* reg_value = duty_ns * MAX_REG_VAL(0xff) / period_ns */
+	val = LGM_PWM_DIV_ROUND_DOWN(duty_cycle << DC_BITS, period);
+	val = min_t(u32, val, MAX_DUTY_CYCLE);
+
+	regmap_update_bits(pc->regmap, PWM_FAN_CON0, PWM_FAN_DC_MSK,
+			   FIELD_PREP(PWM_FAN_DC_MSK, val));
+
+	if (state->enabled != regmap_test_bits(pc->regmap, PWM_FAN_CON0,
+					       PWM_FAN_EN_EN))
+		lgm_pwm_enable(chip, state->enabled);
+
+	return 0;
+}
+
+static void lgm_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+			      struct pwm_state *state)
+{
+	struct lgm_pwm_chip *pc = to_lgm_pwm_chip(chip);
+	u32 duty, val;
+
+	state->enabled = regmap_test_bits(pc->regmap, PWM_FAN_CON0,
+					  PWM_FAN_EN_EN);
+	state->polarity = PWM_POLARITY_NORMAL;
+	state->period = pc->period; /* fixed period */
+
+	regmap_read(pc->regmap, PWM_FAN_CON0, &val);
+	duty = FIELD_GET(PWM_FAN_DC_MSK, val);
+	state->duty_cycle = duty * pc->period >> DC_BITS;
+	state->duty_cycle = roundup_pow_of_two(state->duty_cycle);
+}
+
+static const struct pwm_ops lgm_pwm_ops = {
+	.get_state = lgm_pwm_get_state,
+	.apply = lgm_pwm_apply,
+	.owner = THIS_MODULE,
+};
+
+static void lgm_pwm_init(struct lgm_pwm_chip *pc)
+{
+	struct device *dev = pc->chip.dev;
+	struct regmap *regmap = pc->regmap;
+	u32 max_rpm, fan_wire, con0_val, con0_mask;
+
+	if (device_property_read_u32(dev, "intel,fan-wire", &fan_wire))
+		fan_wire = 2; /* default is 2 wire mode */
+
+	con0_mask = PWM_FAN_MODE_MSK;
+
+	switch (fan_wire) {
+	case 4:
+		con0_val = FIELD_PREP(PWM_FAN_MODE_MSK, PWM_FAN_MODE_4WIRE);
+		pc->period = PERIOD_4WIRE_NSECS;
+		break;
+	default:
+		/* default is 2wire mode */
+		con0_val = FIELD_PREP(PWM_FAN_MODE_MSK, PWM_FAN_MODE_2WIRE);
+		pc->period = PERIOD_2WIRE_NSECS;
+		break;
+	}
+
+	if (device_property_read_u32(dev, "intel,max-rpm", &max_rpm))
+		max_rpm = DFAULT_RPM;
+
+	max_rpm = min_t(u32, max_rpm, MAX_RPM);
+	if (max_rpm == 0)
+		max_rpm = DFAULT_RPM;
+
+	regmap_update_bits(regmap, PWM_FAN_CON1, PWM_FAN_MAX_RPM_MSK, max_rpm);
+	regmap_update_bits(regmap, PWM_FAN_CON0, con0_mask, con0_val);
+}
+
+static const struct regmap_config lgm_pwm_regmap_config = {
+	.reg_bits = 32,
+	.reg_stride = 4,
+	.val_bits = 32,
+};
+
+static int lgm_pwm_probe(struct platform_device *pdev)
+{
+	struct lgm_pwm_chip *pc;
+	struct device *dev = &pdev->dev;
+	void __iomem *io_base;
+	int ret;
+
+	pc = devm_kzalloc(dev, sizeof(*pc), GFP_KERNEL);
+	if (!pc)
+		return -ENOMEM;
+
+	io_base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(io_base))
+		return PTR_ERR(io_base);
+
+	pc->regmap = devm_regmap_init_mmio(dev, io_base, &lgm_pwm_regmap_config);
+	if (IS_ERR(pc->regmap)) {
+		ret = PTR_ERR(pc->regmap);
+		dev_err(dev, "failed to init register map: %pe\n", pc->regmap);
+		return ret;
+	}
+
+	pc->clk = devm_clk_get(dev, NULL);
+	if (IS_ERR(pc->clk)) {
+		ret = PTR_ERR(pc->clk);
+		dev_err(dev, "failed to get clock: %pe\n", pc->clk);
+		return ret;
+	}
+
+	pc->rst = devm_reset_control_get_exclusive(dev, NULL);
+	if (IS_ERR(pc->rst)) {
+		ret = PTR_ERR(pc->rst);
+		dev_err(dev, "failed to get reset control: %pe\n", pc->rst);
+		return ret;
+	}
+
+	ret = reset_control_deassert(pc->rst);
+	if (ret) {
+		dev_err(dev, "cannot deassert reset control: %pe\n",
+			ERR_PTR(ret));
+		return ret;
+	}
+
+	ret = clk_prepare_enable(pc->clk);
+	if (ret) {
+		dev_err(dev, "failed to enable clock\n");
+		return ret;
+	}
+
+	pc->chip.dev = dev;
+	pc->chip.ops = &lgm_pwm_ops;
+	pc->chip.npwm = 1;
+
+	lgm_pwm_init(pc);
+
+	ret = pwmchip_add(&pc->chip);
+	if (ret < 0) {
+		dev_err(dev, "failed to add PWM chip: %pe\n", ERR_PTR(ret));
+		clk_disable_unprepare(pc->clk);
+		reset_control_assert(pc->rst);
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, pc);
+	return 0;
+}
+
+static int lgm_pwm_remove(struct platform_device *pdev)
+{
+	struct lgm_pwm_chip *pc = platform_get_drvdata(pdev);
+	int ret;
+
+	ret = pwmchip_remove(&pc->chip);
+	if (ret < 0)
+		return ret;
+
+	clk_disable_unprepare(pc->clk);
+	reset_control_assert(pc->rst);
+
+	return 0;
+}
+
+static const struct of_device_id lgm_pwm_of_match[] = {
+	{ .compatible = "intel,lgm-pwm" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, lgm_pwm_of_match);
+
+static struct platform_driver lgm_pwm_driver = {
+	.driver = {
+		.name = "intel-pwm",
+		.of_match_table = lgm_pwm_of_match,
+	},
+	.probe = lgm_pwm_probe,
+	.remove = lgm_pwm_remove,
+};
+module_platform_driver(lgm_pwm_driver);
-- 
2.11.0