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@aspeedtech.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Chia-Wei Wang <chiawei_wang@aspeedtech.com>

3 files changed, 260 insertions, 0 deletions

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 669d3fa..6be612d 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -9,6 +9,14 @@ config DM_PWM
 	  frequency/period can be controlled along with the proportion of that
 	  time that the signal is high.
 
+config PWM_ASPEED
+	bool "Enable support for the Aspeed PWM"
+	depends on DM_PWM
+	help
+	  This PWM is found on Ast2600 SoCs. It supports a programmable period
+	  and duty cycle. It provides 16 channels which can be independently
+	  programmed.
+
 config PWM_AT91
 	bool "Enable support for PWM found on AT91 SoC's"
 	depends on DM_PWM && ARCH_AT91
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 55f2bc0..5d31812 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -10,6 +10,7 @@
 
 obj-$(CONFIG_DM_PWM)		+= pwm-uclass.o
 
+obj-$(CONFIG_PWM_ASPEED)	+= pwm-aspeed.o
 obj-$(CONFIG_PWM_AT91)		+= pwm-at91.o
 obj-$(CONFIG_PWM_CROS_EC)	+= cros_ec_pwm.o
 obj-$(CONFIG_PWM_EXYNOS)	+= exynos_pwm.o
diff --git a/drivers/pwm/pwm-aspeed.c b/drivers/pwm/pwm-aspeed.c
new file mode 100644
index 0000000..ba98641
--- /dev/null
+++ b/drivers/pwm/pwm-aspeed.c
@@ -0,0 +1,251 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2022 Aspeed Technology Inc.
+ *
+ * PWM controller driver for Aspeed ast2600 SoCs.
+ * This drivers doesn't support earlier version of the IP.
+ *
+ * The formula of pwm period duration:
+ * period duration = ((DIV_L + 1) * (PERIOD + 1) << DIV_H) / input-clk
+ *
+ * The formula of pwm duty cycle duration:
+ * duty cycle duration = period duration * DUTY_CYCLE_FALLING_POINT / (PERIOD + 1)
+ * = ((DIV_L + 1) * DUTY_CYCLE_FALLING_POINT << DIV_H) / input-clk
+ *
+ * The software driver fixes the period to 255, 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 determine whether the PWM channel is enabled or disabled
+ * 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 determine whether duty_cycle bigger than 0.
+ * PWM_ASPEED_CTRL_INVERSE: When it is toggled the output value will inverse immediately.
+ * PWM_ASPEED_DUTY_CYCLE_FALLING_POINT/PWM_ASPEED_DUTY_CYCLE_RISING_POINT: When these two
+ * values are equal it means the duty cycle = 100%.
+ *
+ * Limitations:
+ * - When changing both duty cycle and period, we cannot prevent in
+ *   software that the output might produce a period with mixed
+ *   settings.
+ * - Disabling the PWM doesn't complete the current period.
+ *
+ * Improvements:
+ * - When only changing one of 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_CTRL_DUTY_SYNC_DISABLE.
+ */
+
+#include <common.h>
+#include <div64.h>
+#include <dm.h>
+#include <pwm.h>
+#include <clk.h>
+#include <reset.h>
+#include <regmap.h>
+#include <syscon.h>
+#include <dm/device_compat.h>
+#include <linux/math64.h>
+#include <linux/bitfield.h>
+#include <asm/io.h>
+
+/* The channel number of Aspeed pwm controller */
+#define PWM_ASPEED_NR_PWMS 16
+
+/* PWM Control Register */
+#define PWM_ASPEED_CTRL(ch) ((ch) * 0x10 + 0x00)
+#define PWM_ASPEED_CTRL_LOAD_SEL_RISING_AS_WDT BIT(19)
+#define PWM_ASPEED_CTRL_DUTY_LOAD_AS_WDT_ENABLE BIT(18)
+#define PWM_ASPEED_CTRL_DUTY_SYNC_DISABLE BIT(17)
+#define PWM_ASPEED_CTRL_CLK_ENABLE BIT(16)
+#define PWM_ASPEED_CTRL_LEVEL_OUTPUT BIT(15)
+#define PWM_ASPEED_CTRL_INVERSE BIT(14)
+#define PWM_ASPEED_CTRL_OPEN_DRAIN_ENABLE BIT(13)
+#define PWM_ASPEED_CTRL_PIN_ENABLE BIT(12)
+#define PWM_ASPEED_CTRL_CLK_DIV_H GENMASK(11, 8)
+#define PWM_ASPEED_CTRL_CLK_DIV_L GENMASK(7, 0)
+
+/* PWM Duty Cycle Register */
+#define PWM_ASPEED_DUTY_CYCLE(ch) ((ch) * 0x10 + 0x04)
+#define PWM_ASPEED_DUTY_CYCLE_PERIOD GENMASK(31, 24)
+#define PWM_ASPEED_DUTY_CYCLE_POINT_AS_WDT GENMASK(23, 16)
+#define PWM_ASPEED_DUTY_CYCLE_FALLING_POINT GENMASK(15, 8)
+#define PWM_ASPEED_DUTY_CYCLE_RISING_POINT GENMASK(7, 0)
+
+/* PWM fixed value */
+#define PWM_ASPEED_FIXED_PERIOD 0xff
+
+#define NSEC_PER_SEC			1000000000L
+
+struct aspeed_pwm_priv {
+	struct clk clk;
+	struct regmap *regmap;
+	struct reset_ctl reset;
+};
+
+static int aspeed_pwm_set_invert(struct udevice *dev, uint channel, bool polarity)
+{
+	struct aspeed_pwm_priv *priv = dev_get_priv(dev);
+
+	if (channel >= PWM_ASPEED_NR_PWMS)
+		return -EINVAL;
+
+	regmap_update_bits(priv->regmap, PWM_ASPEED_CTRL(channel),
+			   PWM_ASPEED_CTRL_INVERSE,
+			   FIELD_PREP(PWM_ASPEED_CTRL_INVERSE,
+				      polarity));
+	return 0;
+}
+
+static int aspeed_pwm_set_enable(struct udevice *dev, uint channel, bool enable)
+{
+	struct aspeed_pwm_priv *priv = dev_get_priv(dev);
+
+	if (channel >= PWM_ASPEED_NR_PWMS)
+		return -EINVAL;
+
+	regmap_update_bits(priv->regmap, PWM_ASPEED_CTRL(channel),
+			   PWM_ASPEED_CTRL_PIN_ENABLE,
+			   enable ? PWM_ASPEED_CTRL_PIN_ENABLE : 0);
+	return 0;
+}
+
+static int aspeed_pwm_set_config(struct udevice *dev, uint channel,
+				 uint period_ns, uint duty_ns)
+{
+	struct aspeed_pwm_priv *priv = dev_get_priv(dev);
+	u32 duty_pt;
+	unsigned long rate;
+	u64 div_h, div_l, divisor;
+	bool clk_en;
+
+	if (channel >= PWM_ASPEED_NR_PWMS)
+		return -EINVAL;
+	dev_dbg(dev, "expect period: %dns, duty_cycle: %dns\n", period_ns,
+		duty_ns);
+
+	rate = clk_get_rate(&priv->clk);
+	/*
+	 * Pick the smallest value for div_h so that div_l can be the biggest
+	 * which results in a finer resolution near the target period value.
+	 */
+	divisor = (u64)NSEC_PER_SEC * (PWM_ASPEED_FIXED_PERIOD + 1) *
+		  (PWM_ASPEED_CTRL_CLK_DIV_L + 1);
+	div_h = order_base_2(div64_u64((u64)rate * period_ns + divisor - 1, divisor));
+	if (div_h > 0xf)
+		div_h = 0xf;
+
+	divisor = ((u64)NSEC_PER_SEC * (PWM_ASPEED_FIXED_PERIOD + 1)) << div_h;
+	div_l = div64_u64((u64)rate * period_ns, divisor);
+
+	if (div_l == 0)
+		return -ERANGE;
+
+	div_l -= 1;
+
+	if (div_l > 255)
+		div_l = 255;
+
+	dev_dbg(dev, "clk source: %ld div_h %lld, div_l : %lld\n", rate, div_h,
+		div_l);
+	/* duty_pt = duty_cycle * (PERIOD + 1) / period */
+	duty_pt = div64_u64(duty_ns * (u64)rate,
+			    (u64)NSEC_PER_SEC * (div_l + 1) << div_h);
+	dev_dbg(dev, "duty_cycle = %d, duty_pt = %d\n", duty_ns,
+		duty_pt);
+
+	if (duty_pt == 0) {
+		clk_en = 0;
+	} else {
+		clk_en = 1;
+		if (duty_pt >= (PWM_ASPEED_FIXED_PERIOD + 1))
+			duty_pt = 0;
+		/*
+		 * Fixed DUTY_CYCLE_PERIOD to its max value to get a
+		 * fine-grained resolution for duty_cycle at the expense of a
+		 * coarser period resolution.
+		 */
+		regmap_update_bits(priv->regmap, PWM_ASPEED_DUTY_CYCLE(channel),
+				   PWM_ASPEED_DUTY_CYCLE_PERIOD |
+				       PWM_ASPEED_DUTY_CYCLE_RISING_POINT |
+				       PWM_ASPEED_DUTY_CYCLE_FALLING_POINT,
+				   FIELD_PREP(PWM_ASPEED_DUTY_CYCLE_PERIOD,
+					      PWM_ASPEED_FIXED_PERIOD) |
+				       FIELD_PREP(PWM_ASPEED_DUTY_CYCLE_FALLING_POINT,
+						  duty_pt));
+	}
+
+	regmap_update_bits(priv->regmap, PWM_ASPEED_CTRL(channel),
+			   PWM_ASPEED_CTRL_CLK_DIV_H |
+			       PWM_ASPEED_CTRL_CLK_DIV_L |
+			       PWM_ASPEED_CTRL_CLK_ENABLE,
+			   FIELD_PREP(PWM_ASPEED_CTRL_CLK_DIV_H, div_h) |
+			       FIELD_PREP(PWM_ASPEED_CTRL_CLK_DIV_L, div_l) |
+			       FIELD_PREP(PWM_ASPEED_CTRL_CLK_ENABLE, clk_en));
+	return 0;
+}
+
+static int aspeed_pwm_probe(struct udevice *dev)
+{
+	int ret;
+	struct aspeed_pwm_priv *priv = dev_get_priv(dev);
+	struct udevice *parent_dev = dev_get_parent(dev);
+
+	priv->regmap = syscon_node_to_regmap(dev_ofnode(dev->parent));
+	if (IS_ERR(priv->regmap)) {
+		dev_err(dev, "Couldn't get regmap\n");
+		return PTR_ERR(priv->regmap);
+	}
+
+	ret = clk_get_by_index(parent_dev, 0, &priv->clk);
+	if (ret < 0) {
+		dev_err(dev, "get clock failed\n");
+		return ret;
+	}
+
+	ret = reset_get_by_index(parent_dev, 0, &priv->reset);
+	if (ret) {
+		dev_err(dev, "get reset failed\n");
+		return ret;
+	}
+	ret = reset_deassert(&priv->reset);
+	if (ret) {
+		dev_err(dev, "cannot deassert reset control: %pe\n",
+			ERR_PTR(ret));
+		return ret;
+	}
+
+	return 0;
+}
+
+static int aspeed_pwm_remove(struct udevice *dev)
+{
+	struct aspeed_pwm_priv *priv = dev_get_priv(dev);
+
+	reset_assert(&priv->reset);
+
+	return 0;
+}
+
+static const struct pwm_ops aspeed_pwm_ops = {
+	.set_invert	= aspeed_pwm_set_invert,
+	.set_config	= aspeed_pwm_set_config,
+	.set_enable	= aspeed_pwm_set_enable,
+};
+
+static const struct udevice_id aspeed_pwm_ids[] = {
+	{ .compatible = "aspeed,ast2600-pwm" },
+	{ }
+};
+
+U_BOOT_DRIVER(aspeed_pwm) = {
+	.name = "aspeed_pwm",
+	.id = UCLASS_PWM,
+	.of_match = aspeed_pwm_ids,
+	.ops = &aspeed_pwm_ops,
+	.probe = aspeed_pwm_probe,
+	.remove = aspeed_pwm_remove,
+	.priv_auto = sizeof(struct aspeed_pwm_priv),
+};