pwm: Add NVIDIA Tegra SoC support

This commit adds a generic PWM framework driver for the PWFM controller
found on NVIDIA Tegra SoCs. The driver is based on code from the
Chromium kernel tree and was originally written by Gary King (NVIDIA)
and later modified by Simon Que (Chromium).
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>

drivers/pwm/Kconfig

@@ -9,4 +9,14 @@ menuconfig PWM
 
 if PWM
 
+config PWM_TEGRA
+	tristate "NVIDIA Tegra PWM support"
+	depends on ARCH_TEGRA
+	help
+	  Generic PWM framework driver for the PWFM controller found on NVIDIA
+	  Tegra SoCs.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-tegra.
+
 endif

drivers/pwm/Makefile

 obj-$(CONFIG_PWM)		+= core.o
+obj-$(CONFIG_PWM_TEGRA)		+= pwm-tegra.o

drivers/pwm/pwm-tegra.c

+/*
+ * drivers/pwm/pwm-tegra.c
+ *
+ * Tegra pulse-width-modulation controller driver
+ *
+ * Copyright (c) 2010, NVIDIA Corporation.
+ * Based on arch/arm/plat-mxc/pwm.c by Sascha Hauer <s.hauer@pengutronix.de>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+ */
+
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/pwm.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+#define PWM_ENABLE	(1 << 31)
+#define PWM_DUTY_WIDTH	8
+#define PWM_DUTY_SHIFT	16
+#define PWM_SCALE_WIDTH	13
+#define PWM_SCALE_SHIFT	0
+
+#define NUM_PWM 4
+
+struct tegra_pwm_chip {
+	struct pwm_chip		chip;
+	struct device		*dev;
+
+	struct clk		*clk;
+
+	void __iomem		*mmio_base;
+};
+
+static inline struct tegra_pwm_chip *to_tegra_pwm_chip(struct pwm_chip *chip)
+{
+	return container_of(chip, struct tegra_pwm_chip, chip);
+}
+
+static inline u32 pwm_readl(struct tegra_pwm_chip *chip, unsigned int num)
+{
+	return readl(chip->mmio_base + (num << 4));
+}
+
+static inline void pwm_writel(struct tegra_pwm_chip *chip, unsigned int num,
+			     unsigned long val)
+{
+	writel(val, chip->mmio_base + (num << 4));
+}
+
+static int tegra_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
+			    int duty_ns, int period_ns)
+{
+	struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
+	unsigned long long c;
+	unsigned long rate, hz;
+	u32 val = 0;
+	int err;
+
+	/*
+	 * Convert from duty_ns / period_ns to a fixed number of duty ticks
+	 * per (1 << PWM_DUTY_WIDTH) cycles and make sure to round to the
+	 * nearest integer during division.
+	 */
+	c = duty_ns * ((1 << PWM_DUTY_WIDTH) - 1) + period_ns / 2;
+	do_div(c, period_ns);
+
+	val = (u32)c << PWM_DUTY_SHIFT;
+
+	/*
+	 * Compute the prescaler value for which (1 << PWM_DUTY_WIDTH)
+	 * cycles at the PWM clock rate will take period_ns nanoseconds.
+	 */
+	rate = clk_get_rate(pc->clk) >> PWM_DUTY_WIDTH;
+	hz = 1000000000ul / period_ns;
+
+	rate = (rate + (hz / 2)) / hz;
+
+	/*
+	 * Since the actual PWM divider is the register's frequency divider
+	 * field minus 1, we need to decrement to get the correct value to
+	 * write to the register.
+	 */
+	if (rate > 0)
+		rate--;
+
+	/*
+	 * Make sure that the rate will fit in the register's frequency
+	 * divider field.
+	 */
+	if (rate >> PWM_SCALE_WIDTH)
+		return -EINVAL;
+
+	val |= rate << PWM_SCALE_SHIFT;
+
+	/*
+	 * If the PWM channel is disabled, make sure to turn on the clock
+	 * before writing the register. Otherwise, keep it enabled.
+	 */
+	if (!test_bit(PWMF_ENABLED, &pwm->flags)) {
+		err = clk_prepare_enable(pc->clk);
+		if (err < 0)
+			return err;
+	} else
+		val |= PWM_ENABLE;
+
+	pwm_writel(pc, pwm->hwpwm, val);
+
+	/*
+	 * If the PWM is not enabled, turn the clock off again to save power.
+	 */
+	if (!test_bit(PWMF_ENABLED, &pwm->flags))
+		clk_disable_unprepare(pc->clk);
+
+	return 0;
+}
+
+static int tegra_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
+	int rc = 0;
+	u32 val;
+
+	rc = clk_prepare_enable(pc->clk);
+	if (rc < 0)
+		return rc;
+
+	val = pwm_readl(pc, pwm->hwpwm);
+	val |= PWM_ENABLE;
+	pwm_writel(pc, pwm->hwpwm, val);
+
+	return 0;
+}
+
+static void tegra_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct tegra_pwm_chip *pc = to_tegra_pwm_chip(chip);
+	u32 val;
+
+	val = pwm_readl(pc, pwm->hwpwm);
+	val &= ~PWM_ENABLE;
+	pwm_writel(pc, pwm->hwpwm, val);
+
+	clk_disable_unprepare(pc->clk);
+}
+
+static const struct pwm_ops tegra_pwm_ops = {
+	.config = tegra_pwm_config,
+	.enable = tegra_pwm_enable,
+	.disable = tegra_pwm_disable,
+	.owner = THIS_MODULE,
+};
+
+static int tegra_pwm_probe(struct platform_device *pdev)
+{
+	struct tegra_pwm_chip *pwm;
+	struct resource *r;
+	int ret;
+
+	pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);
+	if (!pwm) {
+		dev_err(&pdev->dev, "failed to allocate memory\n");
+		return -ENOMEM;
+	}
+
+	pwm->dev = &pdev->dev;
+
+	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!r) {
+		dev_err(&pdev->dev, "no memory resources defined\n");
+		return -ENODEV;
+	}
+
+	pwm->mmio_base = devm_request_and_ioremap(&pdev->dev, r);
+	if (!pwm->mmio_base) {
+		dev_err(&pdev->dev, "failed to ioremap() region\n");
+		return -EADDRNOTAVAIL;
+	}
+
+	platform_set_drvdata(pdev, pwm);
+
+	pwm->clk = clk_get(&pdev->dev, NULL);
+	if (IS_ERR(pwm->clk))
+		return PTR_ERR(pwm->clk);
+
+	pwm->chip.dev = &pdev->dev;
+	pwm->chip.ops = &tegra_pwm_ops;
+	pwm->chip.base = -1;
+	pwm->chip.npwm = NUM_PWM;
+
+	ret = pwmchip_add(&pwm->chip);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
+		clk_put(pwm->clk);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int __devexit tegra_pwm_remove(struct platform_device *pdev)
+{
+	struct tegra_pwm_chip *pc = platform_get_drvdata(pdev);
+	int i;
+
+	if (WARN_ON(!pc))
+		return -ENODEV;
+
+	for (i = 0; i < NUM_PWM; i++) {
+		struct pwm_device *pwm = &pc->chip.pwms[i];
+
+		if (!test_bit(PWMF_ENABLED, &pwm->flags))
+			if (clk_prepare_enable(pc->clk) < 0)
+				continue;
+
+		pwm_writel(pc, i, 0);
+
+		clk_disable_unprepare(pc->clk);
+	}
+
+	pwmchip_remove(&pc->chip);
+	clk_put(pc->clk);
+
+	return 0;
+}
+
+static struct platform_driver tegra_pwm_driver = {
+	.driver = {
+		.name = "tegra-pwm",
+	},
+	.probe = tegra_pwm_probe,
+	.remove = __devexit_p(tegra_pwm_remove),
+};
+
+module_platform_driver(tegra_pwm_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("NVIDIA Corporation");
+MODULE_ALIAS("platform:tegra-pwm");