pwm: sunxi: add support for PWM found on Allwinner A64

This commit adds basic support for PWM found on Allwinner A64.
It can be used for pwm_backlight driver (e.g. for Pinebook)

Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>

arch/arm/include/asm/arch-sunxi/gpio.h

@@ -172,6 +172,7 @@ enum sunxi_gpio_number {
 #define SUN8I_GPD_SDC1		3
 #define SUNXI_GPD_LCD0		2
 #define SUNXI_GPD_LVDS0		3
+#define SUNXI_GPD_PWM		2
 
 #define SUN5I_GPE_SDC2		3
 #define SUN8I_GPE_TWI2		3

arch/arm/include/asm/arch-sunxi/pwm.h

@@ -10,8 +10,15 @@
 #define SUNXI_PWM_CH0_PERIOD		(SUNXI_PWM_BASE + 4)
 
 #define SUNXI_PWM_CTRL_PRESCALE0(x)	((x) & 0xf)
+#define SUNXI_PWM_CTRL_PRESCALE0_MASK	0xf
 #define SUNXI_PWM_CTRL_ENABLE0		(0x5 << 4)
 #define SUNXI_PWM_CTRL_POLARITY0(x)	((x) << 5)
+#define SUNXI_PWM_CTRL_CH0_ACT_STA	BIT(5)
+#define SUNXI_PWM_CTRL_CLK_GATE		BIT(6)
+
+#define SUNXI_PWM_CH0_PERIOD_MAX	(0xffff)
+#define SUNXI_PWM_CH0_PERIOD_PRD(x)	((x & 0xffff) << 16)
+#define SUNXI_PWM_CH0_PERIOD_DUTY(x)	((x) & 0xffff)
 
 #define SUNXI_PWM_PERIOD_80PCT		0x04af03c0
 
@@ -30,4 +37,9 @@
 #define SUNXI_PWM_MUX			SUN8I_GPH_PWM
 #endif
 
+struct sunxi_pwm {
+	u32 ctrl;
+	u32 ch0_period;
+};
+
 #endif

drivers/pwm/Kconfig

@@ -43,3 +43,10 @@ config PWM_TEGRA
 	  four channels with a programmable period and duty cycle. Only a
 	  32KHz clock is supported by the driver but the duty cycle is
 	  configurable.
+
+config PWM_SUNXI
+	bool "Enable support for the Allwinner Sunxi PWM"
+	depends on DM_PWM
+	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.

drivers/pwm/Makefile

@@ -15,3 +15,4 @@ obj-$(CONFIG_PWM_IMX)		+= pwm-imx.o pwm-imx-util.o
 obj-$(CONFIG_PWM_ROCKCHIP)	+= rk_pwm.o
 obj-$(CONFIG_PWM_SANDBOX)	+= sandbox_pwm.o
 obj-$(CONFIG_PWM_TEGRA)		+= tegra_pwm.o
+obj-$(CONFIG_PWM_SUNXI)		+= sunxi_pwm.o

drivers/pwm/sunxi_pwm.c

+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2017-2018 Vasily Khoruzhick <anarsoul@gmail.com>
+ */
+
+#include <common.h>
+#include <div64.h>
+#include <dm.h>
+#include <pwm.h>
+#include <regmap.h>
+#include <syscon.h>
+#include <asm/io.h>
+#include <asm/arch/pwm.h>
+#include <asm/arch/gpio.h>
+#include <power/regulator.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+#define OSC_24MHZ 24000000
+
+struct sunxi_pwm_priv {
+	struct sunxi_pwm *regs;
+	bool invert;
+	u32 prescaler;
+};
+
+static const u32 prescaler_table[] = {
+	120,	/* 0000 */
+	180,	/* 0001 */
+	240,	/* 0010 */
+	360,	/* 0011 */
+	480,	/* 0100 */
+	0,	/* 0101 */
+	0,	/* 0110 */
+	0,	/* 0111 */
+	12000,	/* 1000 */
+	24000,	/* 1001 */
+	36000,	/* 1010 */
+	48000,	/* 1011 */
+	72000,	/* 1100 */
+	0,	/* 1101 */
+	0,	/* 1110 */
+	1,	/* 1111 */
+};
+
+static int sunxi_pwm_config_pinmux(void)
+{
+#ifdef CONFIG_MACH_SUN50I
+	sunxi_gpio_set_cfgpin(SUNXI_GPD(22), SUNXI_GPD_PWM);
+#endif
+	return 0;
+}
+
+static int sunxi_pwm_set_invert(struct udevice *dev, uint channel,
+				bool polarity)
+{
+	struct sunxi_pwm_priv *priv = dev_get_priv(dev);
+
+	debug("%s: polarity=%u\n", __func__, polarity);
+	priv->invert = polarity;
+
+	return 0;
+}
+
+static int sunxi_pwm_set_config(struct udevice *dev, uint channel,
+				uint period_ns, uint duty_ns)
+{
+	struct sunxi_pwm_priv *priv = dev_get_priv(dev);
+	struct sunxi_pwm *regs = priv->regs;
+	int prescaler;
+	u32 v, period = 0, duty;
+	u64 scaled_freq = 0;
+	const u32 nsecs_per_sec = 1000000000U;
+
+	debug("%s: period_ns=%u, duty_ns=%u\n", __func__, period_ns, duty_ns);
+
+	for (prescaler = 0; prescaler < SUNXI_PWM_CTRL_PRESCALE0_MASK;
+	     prescaler++) {
+		if (!prescaler_table[prescaler])
+			continue;
+		scaled_freq = lldiv(OSC_24MHZ, prescaler_table[prescaler]);
+		period = lldiv(scaled_freq * period_ns, nsecs_per_sec);
+		if (period - 1 <= SUNXI_PWM_CH0_PERIOD_MAX)
+			break;
+	}
+
+	if (period - 1 > SUNXI_PWM_CH0_PERIOD_MAX) {
+		debug("%s: failed to find prescaler value\n", __func__);
+		return -EINVAL;
+	}
+
+	duty = lldiv(scaled_freq * duty_ns, nsecs_per_sec);
+
+	if (priv->prescaler != prescaler) {
+		/* Mask clock to update prescaler */
+		v = readl(&regs->ctrl);
+		v &= ~SUNXI_PWM_CTRL_CLK_GATE;
+		writel(v, &regs->ctrl);
+		v &= ~SUNXI_PWM_CTRL_PRESCALE0_MASK;
+		v |= (priv->prescaler & SUNXI_PWM_CTRL_PRESCALE0_MASK);
+		writel(v, &regs->ctrl);
+		v |= SUNXI_PWM_CTRL_CLK_GATE;
+		writel(v, &regs->ctrl);
+		priv->prescaler = prescaler;
+	}
+
+	writel(SUNXI_PWM_CH0_PERIOD_PRD(period) |
+	       SUNXI_PWM_CH0_PERIOD_DUTY(duty), &regs->ch0_period);
+
+	debug("%s: prescaler: %d, period: %d, duty: %d\n",
+	      __func__, priv->prescaler,
+	      period, duty);
+
+	return 0;
+}
+
+static int sunxi_pwm_set_enable(struct udevice *dev, uint channel, bool enable)
+{
+	struct sunxi_pwm_priv *priv = dev_get_priv(dev);
+	struct sunxi_pwm *regs = priv->regs;
+	u32 v;
+
+	debug("%s: Enable '%s'\n", __func__, dev->name);
+
+	v = readl(&regs->ctrl);
+	if (!enable) {
+		v &= ~SUNXI_PWM_CTRL_ENABLE0;
+		writel(v, &regs->ctrl);
+		return 0;
+	}
+
+	sunxi_pwm_config_pinmux();
+
+	if (priv->invert)
+		v &= ~SUNXI_PWM_CTRL_CH0_ACT_STA;
+	else
+		v |= SUNXI_PWM_CTRL_CH0_ACT_STA;
+	v |= SUNXI_PWM_CTRL_ENABLE0;
+	writel(v, &regs->ctrl);
+
+	return 0;
+}
+
+static int sunxi_pwm_ofdata_to_platdata(struct udevice *dev)
+{
+	struct sunxi_pwm_priv *priv = dev_get_priv(dev);
+
+	priv->regs = (struct sunxi_pwm *)devfdt_get_addr(dev);
+
+	return 0;
+}
+
+static int sunxi_pwm_probe(struct udevice *dev)
+{
+	return 0;
+}
+
+static const struct pwm_ops sunxi_pwm_ops = {
+	.set_invert	= sunxi_pwm_set_invert,
+	.set_config	= sunxi_pwm_set_config,
+	.set_enable	= sunxi_pwm_set_enable,
+};
+
+static const struct udevice_id sunxi_pwm_ids[] = {
+	{ .compatible = "allwinner,sun5i-a13-pwm" },
+	{ .compatible = "allwinner,sun50i-a64-pwm" },
+	{ }
+};
+
+U_BOOT_DRIVER(sunxi_pwm) = {
+	.name	= "sunxi_pwm",
+	.id	= UCLASS_PWM,
+	.of_match = sunxi_pwm_ids,
+	.ops	= &sunxi_pwm_ops,
+	.ofdata_to_platdata	= sunxi_pwm_ofdata_to_platdata,
+	.probe		= sunxi_pwm_probe,
+	.priv_auto_alloc_size	= sizeof(struct sunxi_pwm_priv),
+};