pwm: ti: am33xx: add enhanced pwm driver

Enhanced high resolution PWM module (EHRPWM) hardware can be used to
generate PWM output over 2 channels. This commit adds PWM driver support
for EHRPWM device present on AM33XX SOC.

The code is based on the drivers/pwm/pwm-tiehrpwm.c driver of the Linux
kernel version 5.9-rc7.
For DT binding details see:
- Documentation/devicetree/bindings/pwm/pwm-tiehrpwm.txt

Signed-off-by: Dario Binacchi <dariobin@libero.it>

3 files changed, 476 insertions, 0 deletions

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index b3bd5c6..ccf81ab 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -75,3 +75,10 @@ config PWM_SUNXI
 	help
 	  This PWM is found on H3, A64 and other Allwinner SoCs. It supports a
 	  programmable period and duty cycle. A 16-bit counter is used.
+
+config PWM_TI_EHRPWM
+	bool "Enable support for EHRPWM PWM"
+	depends on DM_PWM && ARCH_OMAP2PLUS
+	default y
+	help
+	  PWM driver support for the EHRPWM controller found on TI SOCs.
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index f21ae7d..0b9d269 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -19,3 +19,4 @@ obj-$(CONFIG_PWM_SANDBOX)	+= sandbox_pwm.o
 obj-$(CONFIG_PWM_SIFIVE)	+= pwm-sifive.o
 obj-$(CONFIG_PWM_TEGRA)		+= tegra_pwm.o
 obj-$(CONFIG_PWM_SUNXI)		+= sunxi_pwm.o
+obj-$(CONFIG_PWM_TI_EHRPWM)	+= pwm-ti-ehrpwm.o
diff --git a/drivers/pwm/pwm-ti-ehrpwm.c b/drivers/pwm/pwm-ti-ehrpwm.c
new file mode 100644
index 0000000..ac3d731
--- /dev/null
+++ b/drivers/pwm/pwm-ti-ehrpwm.c
@@ -0,0 +1,468 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * EHRPWM PWM driver
+ *
+ * Copyright (C) 2020 Dario Binacchi <dariobin@libero.it>
+ *
+ * Based on Linux kernel drivers/pwm/pwm-tiehrpwm.c
+ */
+
+#include <common.h>
+#include <clk.h>
+#include <div64.h>
+#include <dm.h>
+#include <dm/device_compat.h>
+#include <pwm.h>
+#include <asm/io.h>
+
+#define NSEC_PER_SEC			        1000000000L
+
+/* Time base module registers */
+#define TI_EHRPWM_TBCTL				0x00
+#define TI_EHRPWM_TBPRD				0x0A
+
+#define TI_EHRPWM_TBCTL_PRDLD_MASK		BIT(3)
+#define TI_EHRPWM_TBCTL_PRDLD_SHDW		0
+#define TI_EHRPWM_TBCTL_PRDLD_IMDT		BIT(3)
+#define TI_EHRPWM_TBCTL_CLKDIV_MASK		GENMASK(12, 7)
+#define TI_EHRPWM_TBCTL_CTRMODE_MASK		GENMASK(1, 0)
+#define TI_EHRPWM_TBCTL_CTRMODE_UP		0
+#define TI_EHRPWM_TBCTL_CTRMODE_DOWN		BIT(0)
+#define TI_EHRPWM_TBCTL_CTRMODE_UPDOWN		BIT(1)
+#define TI_EHRPWM_TBCTL_CTRMODE_FREEZE		GENMASK(1, 0)
+
+#define TI_EHRPWM_TBCTL_HSPCLKDIV_SHIFT		7
+#define TI_EHRPWM_TBCTL_CLKDIV_SHIFT		10
+
+#define TI_EHRPWM_CLKDIV_MAX			7
+#define TI_EHRPWM_HSPCLKDIV_MAX			7
+#define TI_EHRPWM_PERIOD_MAX			0xFFFF
+
+/* Counter compare module registers */
+#define TI_EHRPWM_CMPA				0x12
+#define TI_EHRPWM_CMPB				0x14
+
+/* Action qualifier module registers */
+#define TI_EHRPWM_AQCTLA			0x16
+#define TI_EHRPWM_AQCTLB			0x18
+#define TI_EHRPWM_AQSFRC			0x1A
+#define TI_EHRPWM_AQCSFRC			0x1C
+
+#define TI_EHRPWM_AQCTL_CBU_MASK		GENMASK(9, 8)
+#define TI_EHRPWM_AQCTL_CBU_FRCLOW		BIT(8)
+#define TI_EHRPWM_AQCTL_CBU_FRCHIGH		BIT(9)
+#define TI_EHRPWM_AQCTL_CBU_FRCTOGGLE		GENMASK(9, 8)
+#define TI_EHRPWM_AQCTL_CAU_MASK		GENMASK(5, 4)
+#define TI_EHRPWM_AQCTL_CAU_FRCLOW		BIT(4)
+#define TI_EHRPWM_AQCTL_CAU_FRCHIGH		BIT(5)
+#define TI_EHRPWM_AQCTL_CAU_FRCTOGGLE		GENMASK(5, 4)
+#define TI_EHRPWM_AQCTL_PRD_MASK		GENMASK(3, 2)
+#define TI_EHRPWM_AQCTL_PRD_FRCLOW		BIT(2)
+#define TI_EHRPWM_AQCTL_PRD_FRCHIGH		BIT(3)
+#define TI_EHRPWM_AQCTL_PRD_FRCTOGGLE		GENMASK(3, 2)
+#define TI_EHRPWM_AQCTL_ZRO_MASK		GENMASK(1, 0)
+#define TI_EHRPWM_AQCTL_ZRO_FRCLOW		BIT(0)
+#define TI_EHRPWM_AQCTL_ZRO_FRCHIGH		BIT(1)
+#define TI_EHRPWM_AQCTL_ZRO_FRCTOGGLE		GENMASK(1, 0)
+
+#define TI_EHRPWM_AQCTL_CHANA_POLNORMAL		(TI_EHRPWM_AQCTL_CAU_FRCLOW | \
+						 TI_EHRPWM_AQCTL_PRD_FRCHIGH | \
+						 TI_EHRPWM_AQCTL_ZRO_FRCHIGH)
+#define TI_EHRPWM_AQCTL_CHANA_POLINVERSED	(TI_EHRPWM_AQCTL_CAU_FRCHIGH | \
+						 TI_EHRPWM_AQCTL_PRD_FRCLOW | \
+						 TI_EHRPWM_AQCTL_ZRO_FRCLOW)
+#define TI_EHRPWM_AQCTL_CHANB_POLNORMAL		(TI_EHRPWM_AQCTL_CBU_FRCLOW | \
+						 TI_EHRPWM_AQCTL_PRD_FRCHIGH | \
+						 TI_EHRPWM_AQCTL_ZRO_FRCHIGH)
+#define TI_EHRPWM_AQCTL_CHANB_POLINVERSED	(TI_EHRPWM_AQCTL_CBU_FRCHIGH | \
+						 TI_EHRPWM_AQCTL_PRD_FRCLOW | \
+						 TI_EHRPWM_AQCTL_ZRO_FRCLOW)
+
+#define TI_EHRPWM_AQSFRC_RLDCSF_MASK		GENMASK(7, 6)
+#define TI_EHRPWM_AQSFRC_RLDCSF_ZRO		0
+#define TI_EHRPWM_AQSFRC_RLDCSF_PRD		BIT(6)
+#define TI_EHRPWM_AQSFRC_RLDCSF_ZROPRD		BIT(7)
+#define TI_EHRPWM_AQSFRC_RLDCSF_IMDT		GENMASK(7, 6)
+
+#define TI_EHRPWM_AQCSFRC_CSFB_MASK		GENMASK(3, 2)
+#define TI_EHRPWM_AQCSFRC_CSFB_FRCDIS		0
+#define TI_EHRPWM_AQCSFRC_CSFB_FRCLOW		BIT(2)
+#define TI_EHRPWM_AQCSFRC_CSFB_FRCHIGH		BIT(3)
+#define TI_EHRPWM_AQCSFRC_CSFB_DISSWFRC		GENMASK(3, 2)
+#define TI_EHRPWM_AQCSFRC_CSFA_MASK		GENMASK(1, 0)
+#define TI_EHRPWM_AQCSFRC_CSFA_FRCDIS		0
+#define TI_EHRPWM_AQCSFRC_CSFA_FRCLOW		BIT(0)
+#define TI_EHRPWM_AQCSFRC_CSFA_FRCHIGH		BIT(1)
+#define TI_EHRPWM_AQCSFRC_CSFA_DISSWFRC		GENMASK(1, 0)
+
+#define TI_EHRPWM_NUM_CHANNELS                  2
+
+struct ti_ehrpwm_priv {
+	fdt_addr_t regs;
+	u32 clk_rate;
+	struct clk tbclk;
+	unsigned long period_cycles[TI_EHRPWM_NUM_CHANNELS];
+	bool polarity_reversed[TI_EHRPWM_NUM_CHANNELS];
+};
+
+static void ti_ehrpwm_modify(u16 val, u16 mask, fdt_addr_t reg)
+{
+	unsigned short v;
+
+	v = readw(reg);
+	v &= ~mask;
+	v |= val & mask;
+	writew(v, reg);
+}
+
+static int ti_ehrpwm_set_invert(struct udevice *dev, uint channel,
+				bool polarity)
+{
+	struct ti_ehrpwm_priv *priv = dev_get_priv(dev);
+
+	if (channel >= TI_EHRPWM_NUM_CHANNELS)
+		return -ENOSPC;
+
+	/* Configuration of polarity in hardware delayed, do at enable */
+	priv->polarity_reversed[channel] = polarity;
+	return 0;
+}
+
+/**
+ * set_prescale_div -	Set up the prescaler divider function
+ * @rqst_prescaler:	prescaler value min
+ * @prescale_div:	prescaler value set
+ * @tb_clk_div:		Time Base Control prescaler bits
+ */
+static int set_prescale_div(unsigned long rqst_prescaler, u16 *prescale_div,
+			    u16 *tb_clk_div)
+{
+	unsigned int clkdiv, hspclkdiv;
+
+	for (clkdiv = 0; clkdiv <= TI_EHRPWM_CLKDIV_MAX; clkdiv++) {
+		for (hspclkdiv = 0; hspclkdiv <= TI_EHRPWM_HSPCLKDIV_MAX;
+		     hspclkdiv++) {
+			/*
+			 * calculations for prescaler value :
+			 * prescale_div = HSPCLKDIVIDER * CLKDIVIDER.
+			 * HSPCLKDIVIDER =  2 ** hspclkdiv
+			 * CLKDIVIDER = (1),            if clkdiv == 0 *OR*
+			 *              (2 * clkdiv),   if clkdiv != 0
+			 *
+			 * Configure prescale_div value such that period
+			 * register value is less than 65535.
+			 */
+
+			*prescale_div = (1 << clkdiv) *
+				(hspclkdiv ? (hspclkdiv * 2) : 1);
+			if (*prescale_div > rqst_prescaler) {
+				*tb_clk_div =
+				    (clkdiv << TI_EHRPWM_TBCTL_CLKDIV_SHIFT) |
+				    (hspclkdiv <<
+				     TI_EHRPWM_TBCTL_HSPCLKDIV_SHIFT);
+				return 0;
+			}
+		}
+	}
+
+	return 1;
+}
+
+static void ti_ehrpwm_configure_polarity(struct udevice *dev, uint channel)
+{
+	struct ti_ehrpwm_priv *priv = dev_get_priv(dev);
+	u16 aqctl_val, aqctl_mask;
+	unsigned int aqctl_reg;
+
+	/*
+	 * Configure PWM output to HIGH/LOW level on counter
+	 * reaches compare register value and LOW/HIGH level
+	 * on counter value reaches period register value and
+	 * zero value on counter
+	 */
+	if (channel == 1) {
+		aqctl_reg = TI_EHRPWM_AQCTLB;
+		aqctl_mask = TI_EHRPWM_AQCTL_CBU_MASK;
+
+		if (priv->polarity_reversed[channel])
+			aqctl_val = TI_EHRPWM_AQCTL_CHANB_POLINVERSED;
+		else
+			aqctl_val = TI_EHRPWM_AQCTL_CHANB_POLNORMAL;
+	} else {
+		aqctl_reg = TI_EHRPWM_AQCTLA;
+		aqctl_mask = TI_EHRPWM_AQCTL_CAU_MASK;
+
+		if (priv->polarity_reversed[channel])
+			aqctl_val = TI_EHRPWM_AQCTL_CHANA_POLINVERSED;
+		else
+			aqctl_val = TI_EHRPWM_AQCTL_CHANA_POLNORMAL;
+	}
+
+	aqctl_mask |= TI_EHRPWM_AQCTL_PRD_MASK | TI_EHRPWM_AQCTL_ZRO_MASK;
+	ti_ehrpwm_modify(aqctl_val, aqctl_mask, priv->regs + aqctl_reg);
+}
+
+/*
+ * period_ns = 10^9 * (ps_divval * period_cycles) / PWM_CLK_RATE
+ * duty_ns   = 10^9 * (ps_divval * duty_cycles) / PWM_CLK_RATE
+ */
+static int ti_ehrpwm_set_config(struct udevice *dev, uint channel,
+				uint period_ns, uint duty_ns)
+{
+	struct ti_ehrpwm_priv *priv = dev_get_priv(dev);
+	u32 period_cycles, duty_cycles;
+	u16 ps_divval, tb_divval;
+	unsigned int i, cmp_reg;
+	unsigned long long c;
+
+	if (channel >= TI_EHRPWM_NUM_CHANNELS)
+		return -ENOSPC;
+
+	if (period_ns > NSEC_PER_SEC)
+		return -ERANGE;
+
+	c = priv->clk_rate;
+	c = c * period_ns;
+	do_div(c, NSEC_PER_SEC);
+	period_cycles = (unsigned long)c;
+
+	if (period_cycles < 1) {
+		period_cycles = 1;
+		duty_cycles = 1;
+	} else {
+		c = priv->clk_rate;
+		c = c * duty_ns;
+		do_div(c, NSEC_PER_SEC);
+		duty_cycles = (unsigned long)c;
+	}
+
+	dev_dbg(dev, "channel=%d, period_ns=%d, duty_ns=%d\n",
+		channel, period_ns, duty_ns);
+
+	/*
+	 * Period values should be same for multiple PWM channels as IP uses
+	 * same period register for multiple channels.
+	 */
+	for (i = 0; i < TI_EHRPWM_NUM_CHANNELS; i++) {
+		if (priv->period_cycles[i] &&
+		    priv->period_cycles[i] != period_cycles) {
+			/*
+			 * Allow channel to reconfigure period if no other
+			 * channels being configured.
+			 */
+			if (i == channel)
+				continue;
+
+			dev_err(dev, "period value conflicts with channel %u\n",
+				i);
+			return -EINVAL;
+		}
+	}
+
+	priv->period_cycles[channel] = period_cycles;
+
+	/* Configure clock prescaler to support Low frequency PWM wave */
+	if (set_prescale_div(period_cycles / TI_EHRPWM_PERIOD_MAX, &ps_divval,
+			     &tb_divval)) {
+		dev_err(dev, "unsupported values\n");
+		return -EINVAL;
+	}
+
+	/* Update clock prescaler values */
+	ti_ehrpwm_modify(tb_divval, TI_EHRPWM_TBCTL_CLKDIV_MASK,
+			 priv->regs + TI_EHRPWM_TBCTL);
+
+	/* Update period & duty cycle with presacler division */
+	period_cycles = period_cycles / ps_divval;
+	duty_cycles = duty_cycles / ps_divval;
+
+	/* Configure shadow loading on Period register */
+	ti_ehrpwm_modify(TI_EHRPWM_TBCTL_PRDLD_SHDW, TI_EHRPWM_TBCTL_PRDLD_MASK,
+			 priv->regs + TI_EHRPWM_TBCTL);
+
+	writew(period_cycles, priv->regs + TI_EHRPWM_TBPRD);
+
+	/* Configure ehrpwm counter for up-count mode */
+	ti_ehrpwm_modify(TI_EHRPWM_TBCTL_CTRMODE_UP,
+			 TI_EHRPWM_TBCTL_CTRMODE_MASK,
+			 priv->regs + TI_EHRPWM_TBCTL);
+
+	if (channel == 1)
+		/* Channel 1 configured with compare B register */
+		cmp_reg = TI_EHRPWM_CMPB;
+	else
+		/* Channel 0 configured with compare A register */
+		cmp_reg = TI_EHRPWM_CMPA;
+
+	writew(duty_cycles, priv->regs + cmp_reg);
+	return 0;
+}
+
+static int ti_ehrpwm_disable(struct udevice *dev, uint channel)
+{
+	struct ti_ehrpwm_priv *priv = dev_get_priv(dev);
+	u16 aqcsfrc_val, aqcsfrc_mask;
+	int err;
+
+	if (channel >= TI_EHRPWM_NUM_CHANNELS)
+		return -ENOSPC;
+
+	/* Action Qualifier puts PWM output low forcefully */
+	if (channel) {
+		aqcsfrc_val = TI_EHRPWM_AQCSFRC_CSFB_FRCLOW;
+		aqcsfrc_mask = TI_EHRPWM_AQCSFRC_CSFB_MASK;
+	} else {
+		aqcsfrc_val = TI_EHRPWM_AQCSFRC_CSFA_FRCLOW;
+		aqcsfrc_mask = TI_EHRPWM_AQCSFRC_CSFA_MASK;
+	}
+
+	/* Update shadow register first before modifying active register */
+	ti_ehrpwm_modify(TI_EHRPWM_AQSFRC_RLDCSF_ZRO,
+			 TI_EHRPWM_AQSFRC_RLDCSF_MASK,
+			 priv->regs + TI_EHRPWM_AQSFRC);
+
+	ti_ehrpwm_modify(aqcsfrc_val, aqcsfrc_mask,
+			 priv->regs + TI_EHRPWM_AQCSFRC);
+
+	/*
+	 * Changes to immediate action on Action Qualifier. This puts
+	 * Action Qualifier control on PWM output from next TBCLK
+	 */
+	ti_ehrpwm_modify(TI_EHRPWM_AQSFRC_RLDCSF_IMDT,
+			 TI_EHRPWM_AQSFRC_RLDCSF_MASK,
+			 priv->regs + TI_EHRPWM_AQSFRC);
+
+	ti_ehrpwm_modify(aqcsfrc_val, aqcsfrc_mask,
+			 priv->regs + TI_EHRPWM_AQCSFRC);
+
+	/* Disabling TBCLK on PWM disable */
+	err = clk_disable(&priv->tbclk);
+	if (err) {
+		dev_err(dev, "failed to disable tbclk\n");
+		return err;
+	}
+
+	return 0;
+}
+
+static int ti_ehrpwm_enable(struct udevice *dev, uint channel)
+{
+	struct ti_ehrpwm_priv *priv = dev_get_priv(dev);
+	u16 aqcsfrc_val, aqcsfrc_mask;
+	int err;
+
+	if (channel >= TI_EHRPWM_NUM_CHANNELS)
+		return -ENOSPC;
+
+	/* Disabling Action Qualifier on PWM output */
+	if (channel) {
+		aqcsfrc_val = TI_EHRPWM_AQCSFRC_CSFB_FRCDIS;
+		aqcsfrc_mask = TI_EHRPWM_AQCSFRC_CSFB_MASK;
+	} else {
+		aqcsfrc_val = TI_EHRPWM_AQCSFRC_CSFA_FRCDIS;
+		aqcsfrc_mask = TI_EHRPWM_AQCSFRC_CSFA_MASK;
+	}
+
+	/* Changes to shadow mode */
+	ti_ehrpwm_modify(TI_EHRPWM_AQSFRC_RLDCSF_ZRO,
+			 TI_EHRPWM_AQSFRC_RLDCSF_MASK,
+			 priv->regs + TI_EHRPWM_AQSFRC);
+
+	ti_ehrpwm_modify(aqcsfrc_val, aqcsfrc_mask,
+			 priv->regs + TI_EHRPWM_AQCSFRC);
+
+	/* Channels polarity can be configured from action qualifier module */
+	ti_ehrpwm_configure_polarity(dev, channel);
+
+	err = clk_enable(&priv->tbclk);
+	if (err) {
+		dev_err(dev, "failed to enable tbclk\n");
+		return err;
+	}
+
+	return 0;
+}
+
+static int ti_ehrpwm_set_enable(struct udevice *dev, uint channel, bool enable)
+{
+	if (enable)
+		return ti_ehrpwm_enable(dev, channel);
+
+	return ti_ehrpwm_disable(dev, channel);
+}
+
+static int ti_ehrpwm_of_to_plat(struct udevice *dev)
+{
+	struct ti_ehrpwm_priv *priv = dev_get_priv(dev);
+
+	priv->regs = dev_read_addr(dev);
+	if (priv->regs == FDT_ADDR_T_NONE) {
+		dev_err(dev, "invalid address\n");
+		return -EINVAL;
+	}
+
+	dev_dbg(dev, "regs=0x%08lx\n", priv->regs);
+	return 0;
+}
+
+static int ti_ehrpwm_remove(struct udevice *dev)
+{
+	struct ti_ehrpwm_priv *priv = dev_get_priv(dev);
+
+	clk_release_all(&priv->tbclk, 1);
+	return 0;
+}
+
+static int ti_ehrpwm_probe(struct udevice *dev)
+{
+	struct ti_ehrpwm_priv *priv = dev_get_priv(dev);
+	struct clk clk;
+	int err;
+
+	err = clk_get_by_name(dev, "fck", &clk);
+	if (err) {
+		dev_err(dev, "failed to get clock\n");
+		return err;
+	}
+
+	priv->clk_rate = clk_get_rate(&clk);
+	if (IS_ERR_VALUE(priv->clk_rate) || !priv->clk_rate) {
+		dev_err(dev, "failed to get clock rate\n");
+		if (IS_ERR_VALUE(priv->clk_rate))
+			return priv->clk_rate;
+
+		return -EINVAL;
+	}
+
+	/* Acquire tbclk for Time Base EHRPWM submodule */
+	err = clk_get_by_name(dev, "tbclk", &priv->tbclk);
+	if (err) {
+		dev_err(dev, "failed to get tbclk clock\n");
+		return err;
+	}
+
+	return 0;
+}
+
+static const struct pwm_ops ti_ehrpwm_ops = {
+	.set_config = ti_ehrpwm_set_config,
+	.set_enable = ti_ehrpwm_set_enable,
+	.set_invert = ti_ehrpwm_set_invert,
+};
+
+static const struct udevice_id ti_ehrpwm_ids[] = {
+	{.compatible = "ti,am3352-ehrpwm"},
+	{.compatible = "ti,am33xx-ehrpwm"},
+	{}
+};
+
+U_BOOT_DRIVER(ti_ehrpwm) = {
+	.name = "ti_ehrpwm",
+	.id = UCLASS_PWM,
+	.of_match = ti_ehrpwm_ids,
+	.ops = &ti_ehrpwm_ops,
+	.ofdata_to_platdata = ti_ehrpwm_of_to_plat,
+	.probe = ti_ehrpwm_probe,
+	.remove = ti_ehrpwm_remove,
+	.priv_auto = sizeof(struct ti_ehrpwm_priv),
+};