Message-ID: <20210506061050.8001-3-billy_tsai@aspeedtech.com>
Date:   Thu, 6 May 2021 14:10:50 +0800
From:   Billy Tsai <billy_tsai@...eedtech.com>
To:     <lee.jones@...aro.org>, <robh+dt@...nel.org>, <joel@....id.au>,
        <andrew@...id.au>, <thierry.reding@...il.com>,
        <u.kleine-koenig@...gutronix.de>, <p.zabel@...gutronix.de>,
        <billy_tsai@...eedtech.com>, <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-aspeed@...ts.ozlabs.org>, <linux-kernel@...r.kernel.org>,
        <linux-pwm@...r.kernel.org>
CC:     <BMC-SW@...eedtech.com>
Subject: [v3 2/2] pwm: Add Aspeed ast2600 PWM support

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-function device "pwm-tach controller".

Signed-off-by: Billy Tsai <billy_tsai@...eedtech.com>
---
 drivers/pwm/Kconfig         |   8 +
 drivers/pwm/Makefile        |   1 +
 drivers/pwm/pwm-aspeed-g6.c | 368 ++++++++++++++++++++++++++++++++++++
 3 files changed, 377 insertions(+)
 create mode 100644 drivers/pwm/pwm-aspeed-g6.c

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 63be5362fd3a..b0964b9a3273 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -51,6 +51,14 @@ config PWM_AB8500
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-ab8500.
 
+config PWM_ASPEED_G6
+	tristate "ASPEEDG6 PWM support"
+	depends on ARCH_ASPEED || COMPILE_TEST
+	help
+	  Generic PWM framework driver for ASPEED G6 SoC.
+
+	  This driver provides support for ASPEED G6 PWM controllers.
+
 config PWM_ATMEL
 	tristate "Atmel PWM support"
 	depends on OF
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index cbdcd55d69ee..29d22d806e68 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -2,6 +2,7 @@
 obj-$(CONFIG_PWM)		+= core.o
 obj-$(CONFIG_PWM_SYSFS)		+= sysfs.o
 obj-$(CONFIG_PWM_AB8500)	+= pwm-ab8500.o
+obj-$(CONFIG_PWM_ASPEED_G6)	+= pwm-aspeed-g6.o
 obj-$(CONFIG_PWM_ATMEL)		+= pwm-atmel.o
 obj-$(CONFIG_PWM_ATMEL_HLCDC_PWM)	+= pwm-atmel-hlcdc.o
 obj-$(CONFIG_PWM_ATMEL_TCB)	+= pwm-atmel-tcb.o
diff --git a/drivers/pwm/pwm-aspeed-g6.c b/drivers/pwm/pwm-aspeed-g6.c
new file mode 100644
index 000000000000..f5bb982c21e6
--- /dev/null
+++ b/drivers/pwm/pwm-aspeed-g6.c
@@ -0,0 +1,368 @@
+// 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.
+ *
+ * The formula of pwm frequency:
+ * PWM frequency = CLK Source / ((DIV_L + 1) * BIT(DIV_H) * (PERIOD + 1))
+ *
+ * The software driver fixes the period to 256, which causes the high-frequency
+ * precision of the PWM to be coarse, in exchange for the fineness of the duty cycle.
+ *
+ * Register usage:
+ * PIN_ENABLE: When it is unset the pwm controller will always output low to the extern.
+ * Use to determin PWM channel enable/disable.
+ * CLK_ENABLE: When it is unset the pwm controller will reset the duty counter to 0 and
+ * output low to the PIN_ENABLE mux after that the driver can still change the pwm period
+ * and duty and the value will apply when CLK_ENABLE be set again.
+ * Use to determin whether duty_cycle bigger than 0.
+ * PWM_ASPEED_INVERSE: When it is toggled the output value will inverse immediately.
+ *
+ * Limitations:
+ * - When changing both duty cycle and period, we cannot prevent in
+ *   software that the output might produce a period with mixed
+ *   settings.
+ *
+ * Improvements:
+ * - When changing the duty cycle or period, our pwm controller will not
+ *   generate the glitch, the configure will change at next cycle of pwm.
+ *   This improvement can disable/enable through PWM_ASPEED_DUTY_SYNC_DISABLE.
+ */
+
+#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_ASPEED_LOAD_SEL_RISING_AS_WDT BIT(19)
+#define PWM_ASPEED_DUTY_LOAD_AS_WDT_ENABLE BIT(18)
+#define PWM_ASPEED_DUTY_SYNC_DISABLE BIT(17)
+#define PWM_ASPEED_CLK_ENABLE BIT(16)
+#define PWM_ASPEED_LEVEL_OUTPUT BIT(15)
+#define PWM_ASPEED_INVERSE BIT(14)
+#define PWM_ASPEED_OPEN_DRAIN_ENABLE BIT(13)
+#define PWM_ASPEED_PIN_ENABLE BIT(12)
+#define PWM_ASPEED_CLK_DIV_H GENMASK(11, 8)
+#define PWM_ASPEED_CLK_DIV_L GENMASK(7, 0)
+
+/* PWM Duty Cycle Register */
+#define PWM_ASPEED_DUTY_CYCLE_CH(ch) (((ch * 0x10) + 0x04))
+#define PWM_ASPEED_PERIOD GENMASK(31, 24)
+#define PWM_ASPEED_POINT_AS_WDT GENMASK(23, 16)
+#define PWM_ASPEED_FALLING_POINT GENMASK(15, 8)
+#define PWM_ASPEED_RISING_POINT GENMASK(7, 0)
+
+/* PWM fixed value */
+#define PWM_ASPEED_FIXED_PERIOD 0xff
+
+struct aspeed_pwm_data {
+	struct pwm_chip chip;
+	struct clk *clk;
+	struct regmap *regmap;
+	struct reset_control *reset;
+};
+
+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 void aspeed_set_pwm_clk_enable(struct regmap *regmap, u8 pwm_channel,
+					  bool enable)
+{
+	regmap_update_bits(regmap, PWM_ASPEED_CTRL_CH(pwm_channel),
+			   PWM_ASPEED_CLK_ENABLE,
+			   enable ? PWM_ASPEED_CLK_ENABLE : 0);
+}
+
+static u32 apseed_get_pwm_freq(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct aspeed_pwm_data *priv = aspeed_pwm_chip_to_data(chip);
+	unsigned long rate;
+	u32 index = pwm->hwpwm;
+	u32 div_h, div_l, cur_freq, val;
+
+	rate = clk_get_rate(priv->clk);
+	regmap_read(priv->regmap, PWM_ASPEED_CTRL_CH(index), &val);
+	div_h = FIELD_GET(PWM_ASPEED_CLK_DIV_H, val);
+	div_l = FIELD_GET(PWM_ASPEED_CLK_DIV_L, val);
+
+	cur_freq = DIV_ROUND_DOWN_ULL(rate, (BIT(div_h) * (div_l + 1) *
+					     (PWM_ASPEED_FIXED_PERIOD + 1)));
+	return cur_freq;
+}
+
+static int aspeed_set_pwm_freq(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);
+	unsigned long rate;
+	u32 div_h, div_l, freq;
+	u32 index = pwm->hwpwm;
+	/* Get the smallest value for div_h  */
+	freq = DIV_ROUND_UP_ULL(NSEC_PER_SEC, state->period);
+	rate = clk_get_rate(priv->clk);
+	div_h = DIV_ROUND_DOWN_ULL(rate,
+				   ((FIELD_MAX(PWM_ASPEED_CLK_DIV_L) + 1) *
+				    freq * (PWM_ASPEED_FIXED_PERIOD + 1)));
+	div_h = order_base_2(div_h);
+	if (div_h > 0xf)
+		div_h = 0xf;
+
+	div_l = DIV_ROUND_DOWN_ULL(rate >> div_h,
+				   (freq * (PWM_ASPEED_FIXED_PERIOD + 1)));
+	if (div_l == 0) {
+		dev_err(dev, "Period too small, cannot implement it");
+		return -ERANGE;
+	}
+
+	div_l -= 1;
+
+	if (div_l > 255)
+		div_l = 255;
+
+	dev_dbg(dev, "clk source: %ld div h %x, l : %x\n", rate, div_h, div_l);
+
+	regmap_update_bits(priv->regmap, PWM_ASPEED_CTRL_CH(index),
+			   (PWM_ASPEED_CLK_DIV_H | PWM_ASPEED_CLK_DIV_L),
+			   FIELD_PREP(PWM_ASPEED_CLK_DIV_H, div_h) |
+				   FIELD_PREP(PWM_ASPEED_CLK_DIV_L, div_l));
+	return 0;
+}
+
+static void aspeed_set_pwm_duty(struct pwm_chip *chip, struct pwm_device *pwm,
+				const struct pwm_state *state)
+{
+	struct aspeed_pwm_data *priv = aspeed_pwm_chip_to_data(chip);
+	u32 duty_pt;
+	u32 index = pwm->hwpwm;
+	u32 cur_freq;
+	u64 cur_period;
+
+	cur_freq = apseed_get_pwm_freq(chip, pwm);
+	cur_period = DIV_ROUND_DOWN_ULL(NSEC_PER_SEC, cur_freq);
+	duty_pt = DIV_ROUND_DOWN_ULL(
+		state->duty_cycle * (PWM_ASPEED_FIXED_PERIOD + 1), cur_period);
+	if (duty_pt == 0) {
+		aspeed_set_pwm_clk_enable(priv->regmap, index, false);
+	} else {
+		if (duty_pt >= (PWM_ASPEED_FIXED_PERIOD + 1))
+			duty_pt = 0;
+		/* When duty_pt = 0 it mean our duty cycle = 100% */
+		regmap_update_bits(
+			priv->regmap, PWM_ASPEED_DUTY_CYCLE_CH(index),
+			PWM_ASPEED_FALLING_POINT,
+			FIELD_PREP(PWM_ASPEED_FALLING_POINT, duty_pt));
+		aspeed_set_pwm_clk_enable(priv->regmap, index, true);
+	}
+}
+
+static void aspeed_set_pwm_polarity(struct pwm_chip *chip,
+				    struct pwm_device *pwm,
+				    const struct pwm_state *state)
+{
+	struct aspeed_pwm_data *priv = aspeed_pwm_chip_to_data(chip);
+	u32 index = pwm->hwpwm;
+
+	regmap_update_bits(priv->regmap, PWM_ASPEED_CTRL_CH(index),
+			   PWM_ASPEED_INVERSE,
+			   FIELD_PREP(PWM_ASPEED_INVERSE, state->polarity));
+}
+
+static void aspeed_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+				 struct pwm_state *state)
+{
+	struct device *dev = chip->dev;
+	struct aspeed_pwm_data *priv = aspeed_pwm_chip_to_data(chip);
+	u32 index = pwm->hwpwm;
+	bool polarity, ch_en, clk_en;
+	u32 duty_pt, val;
+	u32 cur_freq;
+
+	regmap_read(priv->regmap, PWM_ASPEED_CTRL_CH(index), &val);
+	polarity = FIELD_GET(PWM_ASPEED_INVERSE, val);
+	ch_en = FIELD_GET(PWM_ASPEED_PIN_ENABLE, val);
+	clk_en = FIELD_GET(PWM_ASPEED_CLK_ENABLE, val);
+	regmap_read(priv->regmap, PWM_ASPEED_DUTY_CYCLE_CH(index), &val);
+	duty_pt = FIELD_GET(PWM_ASPEED_FALLING_POINT, val);
+
+	cur_freq = apseed_get_pwm_freq(chip, pwm);
+
+	state->period = DIV_ROUND_DOWN_ULL(NSEC_PER_SEC, cur_freq);
+	if (clk_en && duty_pt)
+		state->duty_cycle = DIV_ROUND_DOWN_ULL(
+			state->period * duty_pt, PWM_ASPEED_FIXED_PERIOD + 1);
+	else
+		state->duty_cycle = clk_en ? state->period : 0;
+	state->polarity = polarity;
+	state->enabled = ch_en;
+	dev_dbg(dev, "get period: %lldns, duty_cycle: %lldns", state->period,
+		state->duty_cycle);
+}
+
+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);
+	u32 index = pwm->hwpwm;
+	struct pwm_state cur_state;
+	int ret;
+
+	aspeed_pwm_get_state(chip, pwm, &cur_state);
+	dev_dbg(dev, "cur period: %lldns, cur duty_cycle: %lldns",
+		cur_state.period, cur_state.duty_cycle);
+	dev_dbg(dev, "apply period: %lldns, duty_cycle: %lldns", state->period,
+		state->duty_cycle);
+	regmap_update_bits(priv->regmap, PWM_ASPEED_CTRL_CH(index),
+			   PWM_ASPEED_PIN_ENABLE,
+			   state->enabled ? PWM_ASPEED_PIN_ENABLE : 0);
+	if (cur_state.period != state->period) {
+		ret = aspeed_set_pwm_freq(chip, pwm, state);
+		if (ret)
+			return ret;
+		aspeed_set_pwm_duty(chip, pwm, state);
+	} else if (cur_state.duty_cycle != state->duty_cycle)
+		aspeed_set_pwm_duty(chip, pwm, state);
+	aspeed_set_pwm_polarity(chip, pwm, state);
+	return 0;
+}
+
+static const struct pwm_ops aspeed_pwm_ops = {
+	.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, index;
+	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 = of_clk_get(np, 0);
+	if (IS_ERR(priv->clk))
+		return dev_err_probe(dev, PTR_ERR(priv->clk),
+				     "get clock failed\n");
+
+	ret = clk_prepare_enable(priv->clk);
+	if (ret) {
+		dev_err(dev, "couldn't enable clock\n");
+		return ret;
+	}
+
+	priv->reset = of_reset_control_get_shared(np, NULL);
+	if (IS_ERR(priv->reset))
+		return dev_err_probe(dev, PTR_ERR(priv->reset),
+				     "get reset failed\n");
+
+	ret = reset_control_deassert(priv->reset);
+	if (ret) {
+		dev_err(dev, "cannot deassert reset control: %pe\n",
+			ERR_PTR(ret));
+		clk_disable_unprepare(priv->clk);
+		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;
+
+	/*
+	 * Fixed the period to the max value and rising point to 0
+	 * for high resolution and .simplified frequency calculation.
+	 */
+	for (index = 0; index < PWM_ASPEED_NR_PWMS; index++) {
+		regmap_update_bits(
+			priv->regmap, PWM_ASPEED_DUTY_CYCLE_CH(index),
+			PWM_ASPEED_PERIOD,
+			FIELD_PREP(PWM_ASPEED_PERIOD, PWM_ASPEED_FIXED_PERIOD));
+		regmap_update_bits(priv->regmap,
+				   PWM_ASPEED_DUTY_CYCLE_CH(index),
+				   PWM_ASPEED_RISING_POINT, 0);
+	}
+
+	ret = pwmchip_add(&priv->chip);
+	if (ret < 0) {
+		dev_err(dev, "failed to add PWM chip: %pe\n", ERR_PTR(ret));
+		reset_control_assert(priv->reset);
+		clk_disable_unprepare(priv->clk);
+		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);
+
+	pwmchip_remove(&priv->chip);
+	reset_control_assert(priv->reset);
+	clk_disable_unprepare(priv->clk);
+
+	return 0;
+}
+
+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@...eedtech.com>");
+MODULE_DESCRIPTION("ASPEED PWM device driver");
+MODULE_LICENSE("GPL v2");
-- 
2.25.1

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