[v2 2/2] pwm: Add Aspeed ast2600 PWM support

[Billy Tsai <billy_tsai@aspeedtech.com>]

This patch add the support of PWM controller which can be found at aspeed
ast2600 soc. The pwm supoorts up to 16 channels and it's part function
of multi-funciton device "pwm-tach controller".

Signed-off-by: Billy Tsai <billy_tsai@aspeedtech.com>
---
 drivers/pwm/Kconfig         |   7 +
 drivers/pwm/Makefile        |   1 +
 drivers/pwm/pwm-aspeed-g6.c | 324 ++++++++++++++++++++++++++++++++++++
 3 files changed, 332 insertions(+)
 create mode 100644 drivers/pwm/pwm-aspeed-g6.c

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 9a4f66ae8070..d6c1e25717d7 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -42,6 +42,13 @@ config PWM_DEBUG
 	  It is expected to introduce some runtime overhead and diagnostic
 	  output to the kernel log, so only enable while working on a driver.
 
+config PWM_ASPEED_G6
+	tristate "ASPEEDG6 PWM support"
+	depends on ARCH_ASPEED || COMPILE_TEST
+	help
+	  This driver provides support for ASPEED G6 PWM controllers.
+
+
 config PWM_AB8500
 	tristate "AB8500 PWM support"
 	depends on AB8500_CORE && ARCH_U8500
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 6374d3b1d6f3..2d9b4590662e 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_PWM)		+= core.o
 obj-$(CONFIG_PWM_SYSFS)		+= sysfs.o
+obj-$(CONFIG_PWM_ASPEED_G6)	+= pwm-aspeed-g6.o
 obj-$(CONFIG_PWM_AB8500)	+= pwm-ab8500.o
 obj-$(CONFIG_PWM_ATMEL)		+= pwm-atmel.o
 obj-$(CONFIG_PWM_ATMEL_HLCDC_PWM)	+= pwm-atmel-hlcdc.o
diff --git a/drivers/pwm/pwm-aspeed-g6.c b/drivers/pwm/pwm-aspeed-g6.c
new file mode 100644
index 000000000000..b537a5d7015a
--- /dev/null
+++ b/drivers/pwm/pwm-aspeed-g6.c
@@ -0,0 +1,324 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2021 ASPEED Technology Inc.
+ *
+ * PWM controller driver for Aspeed ast26xx SoCs.
+ * This drivers doesn't rollback to previous version of aspeed SoCs.
+ *
+ * Hardware Features:
+ * 1. Support up to 16 channels
+ * 2. Support PWM frequency range from 24Hz to 780KHz
+ * 3. Duty cycle from 0 to 100% with 1/256 resolution incremental
+ * 4. Support wdt reset tolerance (Driver not ready)
+ *
+ */
+
+#include <linux/clk.h>
+#include <linux/errno.h>
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of_platform.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/sysfs.h>
+#include <linux/reset.h>
+#include <linux/regmap.h>
+#include <linux/bitfield.h>
+#include <linux/slab.h>
+#include <linux/pwm.h>
+/* The channel number of Aspeed pwm controller */
+#define PWM_ASPEED_NR_PWMS 16
+
+/* PWM Control Register */
+#define PWM_ASPEED_CTRL_CH(ch) (((ch * 0x10) + 0x00))
+#define PWM_LOAD_SEL_RISING_AS_WDT BIT(19)
+#define PWM_DUTY_LOAD_AS_WDT_ENABLE BIT(18)
+#define PWM_DUTY_SYNC_DISABLE BIT(17)
+#define PWM_CLK_ENABLE BIT(16)
+#define PWM_LEVEL_OUTPUT BIT(15)
+#define PWM_INVERSE BIT(14)
+#define PWM_OPEN_DRAIN_ENABLE BIT(13)
+#define PWM_PIN_ENABLE BIT(12)
+#define PWM_CLK_DIV_H GENMASK(11, 8)
+#define PWM_CLK_DIV_L GENMASK(7, 0)
+
+/* PWM Duty Cycle Register */
+#define PWM_ASPEED_DUTY_CYCLE_CH(ch) (((ch * 0x10) + 0x04))
+#define PWM_PERIOD GENMASK(31, 24)
+#define PWM_POINT_AS_WDT GENMASK(23, 16)
+#define PWM_FALLING_POINT GENMASK(15, 8)
+#define PWM_RISING_POINT GENMASK(7, 0)
+
+/* PWM fixed value */
+#define PWM_FIXED_PERIOD 0xff
+
+struct aspeed_pwm_data {
+	struct pwm_chip chip;
+	struct clk *clk;
+	struct regmap *regmap;
+	struct reset_control *reset;
+};
+
+static void aspeed_set_pwm_channel_enable(struct regmap *regmap, u8 pwm_channel,
+					  bool enable)
+{
+	regmap_update_bits(regmap, PWM_ASPEED_CTRL_CH(pwm_channel),
+			   (PWM_CLK_ENABLE | PWM_PIN_ENABLE),
+			   enable ? (PWM_CLK_ENABLE | PWM_PIN_ENABLE) : 0);
+}
+/*
+ * The PWM frequency = HCLK(200Mhz) / (clock division L bit *
+ * clock division H bit * (period bit + 1))
+ */
+static void aspeed_set_pwm_freq(struct aspeed_pwm_data *priv,
+				struct pwm_device *pwm, u32 freq)
+{
+	u32 target_div, freq_a_fix_div, out_freq;
+	u32 tmp_div_h, tmp_div_l, diff, min_diff = INT_MAX;
+	u32 div_h = BIT(5) - 1, div_l = BIT(8) - 1;
+	u8 div_found;
+	u32 index = pwm->hwpwm;
+	/* Frequency after fixed divide */
+	freq_a_fix_div = clk_get_rate(priv->clk) / (PWM_FIXED_PERIOD + 1);
+	/*
+	 * Use round up to avoid 0 case.
+	 * After that the only scenario which can't find divide pair is too slow
+	 */
+	target_div = DIV_ROUND_UP(freq_a_fix_div, freq);
+	div_found = 0;
+	/* calculate for target frequency */
+	for (tmp_div_h = 0; tmp_div_h < 0x10; tmp_div_h++) {
+		tmp_div_l = target_div / BIT(tmp_div_h) - 1;
+
+		if (tmp_div_l < 0 || tmp_div_l > 255)
+			continue;
+
+		diff = freq - ((freq_a_fix_div >> tmp_div_h) / (tmp_div_l + 1));
+		if (abs(diff) < abs(min_diff)) {
+			min_diff = diff;
+			div_l = tmp_div_l;
+			div_h = tmp_div_h;
+			div_found = 1;
+			if (diff == 0)
+				break;
+		}
+	}
+	if (div_found == 0) {
+		pr_debug("target freq: %d too slow set minimal frequency\n",
+			 freq);
+	}
+	out_freq = freq_a_fix_div / (BIT(div_h) * (div_l + 1));
+	pr_debug("div h %x, l : %x\n", div_h, div_l);
+	pr_debug("hclk %ld, target pwm freq %d, real pwm freq %d\n",
+		 clk_get_rate(priv->clk), freq, out_freq);
+
+	regmap_update_bits(priv->regmap, PWM_ASPEED_CTRL_CH(index),
+			   (PWM_CLK_DIV_H | PWM_CLK_DIV_L),
+			   FIELD_PREP(PWM_CLK_DIV_H, div_h) |
+				   FIELD_PREP(PWM_CLK_DIV_L, div_l));
+}
+
+static void aspeed_set_pwm_duty(struct aspeed_pwm_data *priv,
+				struct pwm_device *pwm, u32 duty_pt)
+{
+	u32 index = pwm->hwpwm;
+
+	if (duty_pt == 0) {
+		aspeed_set_pwm_channel_enable(priv->regmap, index, false);
+	} else {
+		regmap_update_bits(priv->regmap,
+				   PWM_ASPEED_DUTY_CYCLE_CH(index),
+				   PWM_FALLING_POINT,
+				   FIELD_PREP(PWM_FALLING_POINT, duty_pt));
+		aspeed_set_pwm_channel_enable(priv->regmap, index, true);
+	}
+}
+
+static void aspeed_set_pwm_polarity(struct aspeed_pwm_data *priv,
+				    struct pwm_device *pwm, u8 polarity)
+{
+	u32 index = pwm->hwpwm;
+
+	regmap_update_bits(priv->regmap, PWM_ASPEED_CTRL_CH(index), PWM_INVERSE,
+			   (polarity) ? PWM_INVERSE : 0);
+}
+
+static int aspeed_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct device *dev = chip->dev;
+	struct aspeed_pwm_data *priv = dev_get_drvdata(dev);
+	struct pwm_state *channel;
+	u32 index = pwm->hwpwm;
+	/*
+	 * Fixed the period to the max value and rising point to 0
+	 * for high resolution and \bsimplified frequency calculation.
+	 */
+	regmap_update_bits(priv->regmap, PWM_ASPEED_DUTY_CYCLE_CH(index),
+			   PWM_PERIOD,
+			   FIELD_PREP(PWM_PERIOD, PWM_FIXED_PERIOD));
+
+	regmap_update_bits(priv->regmap, PWM_ASPEED_DUTY_CYCLE_CH(index),
+			   PWM_RISING_POINT, 0);
+
+	channel = kzalloc(sizeof(*channel), GFP_KERNEL);
+	if (!channel)
+		return -ENOMEM;
+
+	return pwm_set_chip_data(pwm, channel);
+}
+
+static void aspeed_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct pwm_state *channel = pwm_get_chip_data(pwm);
+
+	kfree(channel);
+}
+
+static inline struct aspeed_pwm_data *
+aspeed_pwm_chip_to_data(struct pwm_chip *c)
+{
+	return container_of(c, struct aspeed_pwm_data, chip);
+}
+
+static int aspeed_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			    const struct pwm_state *state)
+{
+	struct device *dev = chip->dev;
+	struct aspeed_pwm_data *priv = aspeed_pwm_chip_to_data(chip);
+	struct pwm_state *channel = pwm_get_chip_data(pwm);
+	/* compute the ns to Hz */
+	u32 freq = DIV_ROUND_UP_ULL(1000000000, state->period);
+	u32 duty_pt = DIV_ROUND_UP_ULL(
+		state->duty_cycle * (PWM_FIXED_PERIOD + 1), state->period);
+	dev_dbg(dev, "freq: %d, duty_pt: %d", freq, duty_pt);
+	if (state->enabled) {
+		aspeed_set_pwm_freq(priv, pwm, freq);
+		aspeed_set_pwm_duty(priv, pwm, duty_pt);
+		aspeed_set_pwm_polarity(priv, pwm, state->polarity);
+	} else {
+		aspeed_set_pwm_duty(priv, pwm, 0);
+	}
+	channel->period = state->period;
+	channel->duty_cycle = state->duty_cycle;
+	channel->polarity = state->polarity;
+	channel->enabled = state->enabled;
+
+	return 0;
+}
+
+static void aspeed_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+				 struct pwm_state *state)
+{
+	struct pwm_state *channel = pwm_get_chip_data(pwm);
+
+	state->period = channel->period;
+	state->duty_cycle = channel->duty_cycle;
+	state->polarity = channel->polarity;
+	state->enabled = channel->enabled;
+}
+
+static const struct pwm_ops aspeed_pwm_ops = {
+	.request = aspeed_pwm_request,
+	.free = aspeed_pwm_free,
+	.apply = aspeed_pwm_apply,
+	.get_state = aspeed_pwm_get_state,
+	.owner = THIS_MODULE,
+};
+
+static int aspeed_pwm_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	int ret;
+	struct aspeed_pwm_data *priv;
+	struct device_node *np;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	np = pdev->dev.parent->of_node;
+	if (!of_device_is_compatible(np, "aspeed,ast2600-pwm-tach")) {
+		dev_err(dev, "unsupported pwm device binding\n");
+		return -ENODEV;
+	}
+
+	priv->regmap = syscon_node_to_regmap(np);
+	if (IS_ERR(priv->regmap)) {
+		dev_err(dev, "Couldn't get regmap\n");
+		return -ENODEV;
+	}
+
+	priv->clk = devm_clk_get(dev, NULL);
+	if (IS_ERR(priv->clk))
+		return -ENODEV;
+
+	ret = clk_prepare_enable(priv->clk);
+	if (ret) {
+		dev_err(dev, "couldn't enable clock\n");
+		return ret;
+	}
+
+	priv->reset = reset_control_get_shared(dev, NULL);
+	if (IS_ERR(priv->reset)) {
+		dev_err(dev, "can't get aspeed_pwm_tacho reset: %pe\n",
+			ERR_PTR((long)priv->reset));
+		return PTR_ERR(priv->reset);
+	}
+
+	ret = reset_control_deassert(priv->reset);
+	if (ret) {
+		dev_err(&pdev->dev, "cannot deassert reset control: %pe\n",
+			ERR_PTR(ret));
+		return ret;
+	}
+
+	priv->chip.dev = dev;
+	priv->chip.ops = &aspeed_pwm_ops;
+	priv->chip.npwm = PWM_ASPEED_NR_PWMS;
+	priv->chip.of_xlate = of_pwm_xlate_with_flags;
+	priv->chip.of_pwm_n_cells = 3;
+
+	ret = pwmchip_add(&priv->chip);
+	if (ret < 0) {
+		dev_err(dev, "failed to add PWM chip: %pe\n", ERR_PTR(ret));
+		return ret;
+	}
+	dev_set_drvdata(dev, priv);
+	return ret;
+}
+
+static int aspeed_pwm_remove(struct platform_device *dev)
+{
+	struct aspeed_pwm_data *priv = platform_get_drvdata(dev);
+
+	reset_control_assert(priv->reset);
+	clk_disable_unprepare(priv->clk);
+
+	return pwmchip_remove(&priv->chip);
+}
+
+static const struct of_device_id of_pwm_match_table[] = {
+	{
+		.compatible = "aspeed,ast2600-pwm",
+	},
+	{},
+};
+MODULE_DEVICE_TABLE(of, of_pwm_match_table);
+
+static struct platform_driver aspeed_pwm_driver = {
+	.probe		= aspeed_pwm_probe,
+	.remove		= aspeed_pwm_remove,
+	.driver		= {
+		.name	= "aspeed_pwm",
+		.of_match_table = of_pwm_match_table,
+	},
+};
+
+module_platform_driver(aspeed_pwm_driver);
+
+MODULE_AUTHOR("Billy Tsai <billy_tsai@aspeedtech.com>");
+MODULE_DESCRIPTION("ASPEED PWM device driver");
+MODULE_LICENSE("GPL v2");
-- 
2.25.1