tegra: pwm: Add a driver for the tegra PWM

This PWM supports four channels. The driver always uses the 32KHz clock,
and adjusts the duty cycle accordingly.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Warren <twarren@nvidia.com>

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

@@ -27,6 +27,7 @@ struct pwm_ctlr {
 #define PWM_DIVIDER_SHIFT	0
 #define PWM_DIVIDER_MASK	(0x1FFF << PWM_DIVIDER_SHIFT)
 
+#ifndef CONFIG_PWM
 /**
  * Program the PWM with the given parameters.
  *
@@ -56,5 +57,6 @@ int pwm_request(const void *blob, int node, const char *prop_name);
  * @return 0 if ok, -1 if the device tree node was not found or invalid.
  */
 int pwm_init(const void *blob);
+#endif
 
 #endif	/* __ASM_ARCH_TEGRA_PWM_H */

drivers/pwm/Makefile

@@ -13,3 +13,6 @@
 obj-$(CONFIG_DM_PWM) += pwm-uclass.o
 obj-$(CONFIG_PWM_ROCKCHIP) += rk_pwm.o
 obj-$(CONFIG_PWM_IMX) += pwm-imx.o pwm-imx-util.o
+ifdef CONFIG_DM_PWM
+obj-$(CONFIG_PWM_TEGRA) += tegra_pwm.o
+endif

drivers/pwm/tegra_pwm.c

@@ -0,0 +1,85 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * SPDX-License-Identifier:     GPL-2.0+
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <pwm.h>
+#include <asm/io.h>
+#include <asm/arch/clock.h>
+#include <asm/arch/pwm.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+struct tegra_pwm_priv {
+	struct pwm_ctlr *regs;
+};
+
+static int tegra_pwm_set_config(struct udevice *dev, uint channel,
+				uint period_ns, uint duty_ns)
+{
+	struct tegra_pwm_priv *priv = dev_get_priv(dev);
+	struct pwm_ctlr *regs = priv->regs;
+	uint pulse_width;
+	u32 reg;
+
+	if (channel >= 4)
+		return -EINVAL;
+	debug("%s: Configure '%s' channel %u\n", __func__, dev->name, channel);
+	/* We ignore the period here and just use 32KHz */
+	clock_start_periph_pll(PERIPH_ID_PWM, CLOCK_ID_SFROM32KHZ, 32768);
+
+	pulse_width = duty_ns * 255 / period_ns;
+
+	reg = pulse_width << PWM_WIDTH_SHIFT;
+	reg |= 1 << PWM_DIVIDER_SHIFT;
+	writel(reg, &regs[channel].control);
+	debug("%s: pulse_width=%u\n", __func__, pulse_width);
+
+	return 0;
+}
+
+static int tegra_pwm_set_enable(struct udevice *dev, uint channel, bool enable)
+{
+	struct tegra_pwm_priv *priv = dev_get_priv(dev);
+	struct pwm_ctlr *regs = priv->regs;
+
+	if (channel >= 4)
+		return -EINVAL;
+	debug("%s: Enable '%s' channel %u\n", __func__, dev->name, channel);
+	clrsetbits_le32(&regs[channel].control, PWM_ENABLE_MASK,
+			enable ? PWM_ENABLE_MASK : 0);
+
+	return 0;
+}
+
+static int tegra_pwm_ofdata_to_platdata(struct udevice *dev)
+{
+	struct tegra_pwm_priv *priv = dev_get_priv(dev);
+
+	priv->regs = (struct pwm_ctlr *)dev_get_addr(dev);
+
+	return 0;
+}
+
+static const struct pwm_ops tegra_pwm_ops = {
+	.set_config	= tegra_pwm_set_config,
+	.set_enable	= tegra_pwm_set_enable,
+};
+
+static const struct udevice_id tegra_pwm_ids[] = {
+	{ .compatible = "nvidia,tegra124-pwm" },
+	{ .compatible = "nvidia,tegra20-pwm" },
+	{ }
+};
+
+U_BOOT_DRIVER(tegra_pwm) = {
+	.name	= "tegra_pwm",
+	.id	= UCLASS_PWM,
+	.of_match = tegra_pwm_ids,
+	.ops	= &tegra_pwm_ops,
+	.ofdata_to_platdata	= tegra_pwm_ofdata_to_platdata,
+	.priv_auto_alloc_size	= sizeof(struct tegra_pwm_priv),
+};