Re: [PATCH 3/4] pwm: Add Aspeed ast2600 PWM support

This patch add the support of PWM controller which can find at aspeed
ast2600 soc chip. This controller supoorts up to 16 channels.

Signed-off-by: Billy Tsai <billy_tsai@aspeedtech.com>
---
 drivers/pwm/pwm-aspeed-g6.c | 291 ++++++++++++++++++++++++++++++++++++
 1 file changed, 291 insertions(+)
 create mode 100644 drivers/pwm/pwm-aspeed-g6.c

diff --git a/drivers/pwm/pwm-aspeed-g6.c b/drivers/pwm/pwm-aspeed-g6.c
new file mode 100644
index 000000000000..4bb4f97453c6
--- /dev/null
+++ b/drivers/pwm/pwm-aspeed-g6.c

@@ -0,0 +1,291 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) ASPEED Technology Inc.

+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 or later as
+ * published by the Free Software Foundation.

+
+#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/pwm.h>
+/* The channel number of Aspeed pwm controller */
+#define ASPEED_NR_PWMS 16
+/* PWM Control Register */
+#define ASPEED_PWM_CTRL_CH(ch) ((ch * 0x10) + 0x00)

+#define PWM_LOAD_SEL_AS_WDT BIT(19)
+#define LOAD_SEL_FALLING 0
+#define LOAD_SEL_RIGING 1
+#define PWM_DUTY_LOAD_AS_WDT_EN BIT(18)
+#define PWM_DUTY_SYNC_DIS BIT(17)
+#define PWM_CLK_ENABLE BIT(16)
+#define PWM_LEVEL_OUTPUT BIT(15)
+#define PWM_INVERSE BIT(14)
+#define PWM_OPEN_DRAIN_EN BIT(13)
+#define PWM_PIN_EN BIT(12)
+#define PWM_CLK_DIV_H_SHIFT 8
+#define PWM_CLK_DIV_H_MASK (0xf << PWM_CLK_DIV_H_SHIFT)
+#define PWM_CLK_DIV_L_SHIFT 0
+#define PWM_CLK_DIV_L_MASK (0xff << PWM_CLK_DIV_L_SHIFT)
+/* PWM Duty Cycle Register */
+#define ASPEED_PWM_DUTY_CYCLE_CH(ch) ((ch * 0x10) + 0x04)
+#define PWM_PERIOD_SHIFT (24)
+#define PWM_PERIOD_MASK (0xff << PWM_PERIOD_SHIFT)
+#define PWM_POINT_AS_WDT_SHIFT (16)
+#define PWM_POINT_AS_WDT_MASK (0xff << PWM_POINT_AS_WDT_SHIFT)
+#define PWM_FALLING_POINT_SHIFT (8)
+#define PWM_FALLING_POINT_MASK (0xffff << PWM_FALLING_POINT_SHIFT)
+#define PWM_RISING_POINT_SHIFT (0)
+#define PWM_RISING_POINT_MASK (0xffff << PWM_RISING_POINT_SHIFT)
+/* PWM default value */
+#define DEFAULT_PWM_PERIOD 0xff
+#define DEFAULT_TARGET_PWM_FREQ 25000
+#define DEFAULT_DUTY_PT 10
+#define DEFAULT_WDT_RELOAD_DUTY_PT 16

+struct aspeed_pwm_data {
+	struct pwm_chip chip;
+	struct regmap *regmap;
+	unsigned long clk_freq;
+	struct reset_control *reset;
+};
+/**
+ * struct aspeed_pwm - per-PWM driver data
+ * @freq: cached pwm freq
+ */
+struct aspeed_pwm {
+	u32 freq;
+};

+static void aspeed_set_pwm_channel_enable(struct regmap *regmap, u8 pwm_channel,
+					  bool enable)
+{
+	regmap_update_bits(regmap, ASPEED_PWM_CTRL_CH(pwm_channel),
+			   (PWM_CLK_ENABLE | PWM_PIN_EN),
+			   enable ? (PWM_CLK_ENABLE | PWM_PIN_EN) : 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, cal_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;
+	struct aspeed_pwm *channel = pwm_get_chip_data(pwm);
+
+	cal_freq = priv->clk_freq / (DEFAULT_PWM_PERIOD + 1);
+	target_div = DIV_ROUND_UP(cal_freq, freq);
+	div_found = 0;
+	/* calculate for target frequence */

+	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 - cal_freq / (BIT(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);
+	}
+	channel->freq = cal_freq / (BIT(div_h) * (div_l + 1));
+	pr_debug("div h %x, l : %x pwm out clk %d\n", div_h, div_l,
+		 channel->freq);
+	pr_debug("hclk %ld, target pwm freq %d, real pwm freq %d\n",
+		 priv->clk_freq, freq, channel->freq);
+
+	regmap_update_bits(priv->regmap, ASPEED_PWM_CTRL_CH(index),
+			   (PWM_CLK_DIV_H_MASK | PWM_CLK_DIV_L_MASK),
+			   (div_h << PWM_CLK_DIV_H_SHIFT) |
+				   (div_l << PWM_CLK_DIV_L_SHIFT));
+}
+
+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,
+				   ASPEED_PWM_DUTY_CYCLE_CH(index),
+				   PWM_FALLING_POINT_MASK,
+				   duty_pt << PWM_FALLING_POINT_SHIFT);
+		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, ASPEED_PWM_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 aspeed_pwm *channel;
+	u32 index = pwm->hwpwm;
+	/*
+	 * Fixed the period to the max value and rising point to 0
+	 * for high resolution and simplified frequency calculation.

+	 */
+	regmap_update_bits(priv->regmap, ASPEED_PWM_DUTY_CYCLE_CH(index),
+			   PWM_PERIOD_MASK,
+			   DEFAULT_PWM_PERIOD << PWM_PERIOD_SHIFT);
+
+	regmap_update_bits(priv->regmap, ASPEED_PWM_DUTY_CYCLE_CH(index),
+			   PWM_RISING_POINT_MASK, 0);

+	channel = devm_kzalloc(dev, sizeof(*channel), GFP_KERNEL);
+	if (!channel)
+		return -ENOMEM;

+	pwm_set_chip_data(pwm, channel);
+
+	return 0;

+}
+
+static void aspeed_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct device *dev = chip->dev;
+	struct aspeed_pwm *channel = pwm_get_chip_data(pwm);
+
+	devm_kfree(dev, channel);
+}
+
+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 = dev_get_drvdata(dev);

+	struct pwm_state *cur_state = &pwm->state;
+	u32 freq = DIV_ROUND_UP_ULL(1000000000, state->period);
+	u32 duty_pt = DIV_ROUND_UP_ULL(
+		state->duty_cycle * (DEFAULT_PWM_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);
+	}
+	cur_state->period = state->period;
+	cur_state->duty_cycle = state->duty_cycle;
+	cur_state->polarity = state->polarity;
+	cur_state->enabled = state->enabled;

+static const struct pwm_ops aspeed_pwm_ops = {
+	.request = aspeed_pwm_request,
+	.free = aspeed_pwm_free,
+	.apply = aspeed_pwm_apply,

+	.owner = THIS_MODULE,
+};
+
+static int aspeed_pwm_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct clk *clk;
+	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;
+	}
+
+	clk = devm_clk_get(dev, NULL);
+	if (IS_ERR(clk))
+		return -ENODEV;
+	priv->clk_freq = clk_get_rate(clk);

+	priv->reset = reset_control_get_shared(&pdev->dev, NULL);
+	if (IS_ERR(priv->reset)) {
+		dev_err(&pdev->dev, "can't get aspeed_pwm_tacho reset\n");
+		return PTR_ERR(priv->reset);
+	}
+	reset_control_deassert(priv->reset);

+	priv->chip.dev = dev;
+	priv->chip.ops = &aspeed_pwm_ops;
+	priv->chip.base = -1;

+	priv->chip.npwm = 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(&pdev->dev, "failed to add PWM chip: %d\n", ret);

+		return ret;
+	}
+	dev_set_drvdata(dev, priv);
+	return ret;
+}
+
+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,

+	.driver		= {
+		.name	= "aspeed_pwm",
+		.of_match_table = of_pwm_match_table,
+	},
+};