pwm: Add PWM driver for OMAP using dual-mode timers

Adds support for using a OMAP dual-mode timer with PWM capability
as a Linux PWM device. The driver controls the timer by using the
dmtimer API.

Add a platform_data structure for each pwm-omap-dmtimer nodes containing
the dmtimers functions in order to get driver not rely on platform
specific functions.

Cc: Grant Erickson <marathon96@gmail.com>
Cc: NeilBrown <neilb@suse.de>
Cc: Joachim Eastwood <manabian@gmail.com>
Suggested-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Tony Lindgren <tony@atomide.com>
[thierry.reding@gmail.com: coding style bikeshed, fix timer leak]
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

Documentation/devicetree/bindings/pwm/pwm-omap-dmtimer.txt

@@ -0,0 +1,18 @@
+* OMAP PWM for dual-mode timers
+
+Required properties:
+- compatible: Shall contain "ti,omap-dmtimer-pwm".
+- ti,timers: phandle to PWM capable OMAP timer. See arm/omap/timer.txt for info
+  about these timers.
+- #pwm-cells: Should be 3. See pwm.txt in this directory for a description of
+  the cells format.
+
+Optional properties:
+- ti,prescaler: Should be a value between 0 and 7, see the timers datasheet
+
+Example:
+	pwm9: dmtimer-pwm@9 {
+		compatible = "ti,omap-dmtimer-pwm";
+		ti,timers = <&timer9>;
+		#pwm-cells = <3>;
+	};

drivers/pwm/Kconfig

@@ -265,6 +265,15 @@ config PWM_MXS
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-mxs.
 
+config PWM_OMAP_DMTIMER
+	tristate "OMAP Dual-Mode Timer PWM support"
+	depends on OF && ARCH_OMAP && OMAP_DM_TIMER
+	help
+	  Generic PWM framework driver for OMAP Dual-Mode Timer PWM output
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-omap-dmtimer
+
 config PWM_PCA9685
 	tristate "NXP PCA9685 PWM driver"
 	depends on I2C

drivers/pwm/Makefile

@@ -24,6 +24,7 @@ obj-$(CONFIG_PWM_LPSS_PCI)	+= pwm-lpss-pci.o
 obj-$(CONFIG_PWM_LPSS_PLATFORM)	+= pwm-lpss-platform.o
 obj-$(CONFIG_PWM_MTK_DISP)	+= pwm-mtk-disp.o
 obj-$(CONFIG_PWM_MXS)		+= pwm-mxs.o
+obj-$(CONFIG_PWM_OMAP_DMTIMER)	+= pwm-omap-dmtimer.o
 obj-$(CONFIG_PWM_PCA9685)	+= pwm-pca9685.o
 obj-$(CONFIG_PWM_PUV3)		+= pwm-puv3.o
 obj-$(CONFIG_PWM_PXA)		+= pwm-pxa.o

drivers/pwm/pwm-omap-dmtimer.c

@@ -0,0 +1,327 @@
+/*
+ * Copyright (c) 2015 Neil Armstrong <narmstrong@baylibre.com>
+ * Copyright (c) 2014 Joachim Eastwood <manabian@gmail.com>
+ * Copyright (c) 2012 NeilBrown <neilb@suse.de>
+ * Heavily based on earlier code which is:
+ * Copyright (c) 2010 Grant Erickson <marathon96@gmail.com>
+ *
+ * Also based on pwm-samsung.c
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * Description:
+ *   This file is the core OMAP support for the generic, Linux
+ *   PWM driver / controller, using the OMAP's dual-mode timers.
+ */
+
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/platform_data/pwm_omap_dmtimer.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+#include <linux/pwm.h>
+#include <linux/slab.h>
+#include <linux/time.h>
+
+#define DM_TIMER_LOAD_MIN 0xfffffffe
+
+struct pwm_omap_dmtimer_chip {
+	struct pwm_chip chip;
+	struct mutex mutex;
+	pwm_omap_dmtimer *dm_timer;
+	struct pwm_omap_dmtimer_pdata *pdata;
+	struct platform_device *dm_timer_pdev;
+};
+
+static inline struct pwm_omap_dmtimer_chip *
+to_pwm_omap_dmtimer_chip(struct pwm_chip *chip)
+{
+	return container_of(chip, struct pwm_omap_dmtimer_chip, chip);
+}
+
+static int pwm_omap_dmtimer_calc_value(unsigned long clk_rate, int ns)
+{
+	u64 c = (u64)clk_rate * ns;
+
+	do_div(c, NSEC_PER_SEC);
+
+	return DM_TIMER_LOAD_MIN - c;
+}
+
+static void pwm_omap_dmtimer_start(struct pwm_omap_dmtimer_chip *omap)
+{
+	/*
+	 * According to OMAP 4 TRM section 22.2.4.10 the counter should be
+	 * started at 0xFFFFFFFE when overflow and match is used to ensure
+	 * that the PWM line is toggled on the first event.
+	 *
+	 * Note that omap_dm_timer_enable/disable is for register access and
+	 * not the timer counter itself.
+	 */
+	omap->pdata->enable(omap->dm_timer);
+	omap->pdata->write_counter(omap->dm_timer, DM_TIMER_LOAD_MIN);
+	omap->pdata->disable(omap->dm_timer);
+
+	omap->pdata->start(omap->dm_timer);
+}
+
+static int pwm_omap_dmtimer_enable(struct pwm_chip *chip,
+				   struct pwm_device *pwm)
+{
+	struct pwm_omap_dmtimer_chip *omap = to_pwm_omap_dmtimer_chip(chip);
+
+	mutex_lock(&omap->mutex);
+	pwm_omap_dmtimer_start(omap);
+	mutex_unlock(&omap->mutex);
+
+	return 0;
+}
+
+static void pwm_omap_dmtimer_disable(struct pwm_chip *chip,
+				     struct pwm_device *pwm)
+{
+	struct pwm_omap_dmtimer_chip *omap = to_pwm_omap_dmtimer_chip(chip);
+
+	mutex_lock(&omap->mutex);
+	omap->pdata->stop(omap->dm_timer);
+	mutex_unlock(&omap->mutex);
+}
+
+static int pwm_omap_dmtimer_config(struct pwm_chip *chip,
+				   struct pwm_device *pwm,
+				   int duty_ns, int period_ns)
+{
+	struct pwm_omap_dmtimer_chip *omap = to_pwm_omap_dmtimer_chip(chip);
+	int load_value, match_value;
+	struct clk *fclk;
+	unsigned long clk_rate;
+	bool timer_active;
+
+	dev_dbg(chip->dev, "duty cycle: %d, period %d\n", duty_ns, period_ns);
+
+	mutex_lock(&omap->mutex);
+	if (duty_ns == pwm_get_duty_cycle(pwm) &&
+	    period_ns == pwm_get_period(pwm)) {
+		/* No change - don't cause any transients. */
+		mutex_unlock(&omap->mutex);
+		return 0;
+	}
+
+	fclk = omap->pdata->get_fclk(omap->dm_timer);
+	if (!fclk) {
+		dev_err(chip->dev, "invalid pmtimer fclk\n");
+		mutex_unlock(&omap->mutex);
+		return -EINVAL;
+	}
+
+	clk_rate = clk_get_rate(fclk);
+	if (!clk_rate) {
+		dev_err(chip->dev, "invalid pmtimer fclk rate\n");
+		mutex_unlock(&omap->mutex);
+		return -EINVAL;
+	}
+
+	dev_dbg(chip->dev, "clk rate: %luHz\n", clk_rate);
+
+	/*
+	 * Calculate the appropriate load and match values based on the
+	 * specified period and duty cycle. The load value determines the
+	 * cycle time and the match value determines the duty cycle.
+	 */
+	load_value = pwm_omap_dmtimer_calc_value(clk_rate, period_ns);
+	match_value = pwm_omap_dmtimer_calc_value(clk_rate,
+						  period_ns - duty_ns);
+
+	/*
+	 * We MUST stop the associated dual-mode timer before attempting to
+	 * write its registers, but calls to omap_dm_timer_start/stop must
+	 * be balanced so check if timer is active before calling timer_stop.
+	 */
+	timer_active = pm_runtime_active(&omap->dm_timer_pdev->dev);
+	if (timer_active)
+		omap->pdata->stop(omap->dm_timer);
+
+	omap->pdata->set_load(omap->dm_timer, true, load_value);
+	omap->pdata->set_match(omap->dm_timer, true, match_value);
+
+	dev_dbg(chip->dev, "load value: %#08x (%d), match value: %#08x (%d)\n",
+		load_value, load_value,	match_value, match_value);
+
+	omap->pdata->set_pwm(omap->dm_timer,
+			      pwm->polarity == PWM_POLARITY_INVERSED,
+			      true,
+			      PWM_OMAP_DMTIMER_TRIGGER_OVERFLOW_AND_COMPARE);
+
+	/* If config was called while timer was running it must be reenabled. */
+	if (timer_active)
+		pwm_omap_dmtimer_start(omap);
+
+	mutex_unlock(&omap->mutex);
+
+	return 0;
+}
+
+static int pwm_omap_dmtimer_set_polarity(struct pwm_chip *chip,
+					 struct pwm_device *pwm,
+					 enum pwm_polarity polarity)
+{
+	struct pwm_omap_dmtimer_chip *omap = to_pwm_omap_dmtimer_chip(chip);
+
+	/*
+	 * PWM core will not call set_polarity while PWM is enabled so it's
+	 * safe to reconfigure the timer here without stopping it first.
+	 */
+	mutex_lock(&omap->mutex);
+	omap->pdata->set_pwm(omap->dm_timer,
+			      polarity == PWM_POLARITY_INVERSED,
+			      true,
+			      PWM_OMAP_DMTIMER_TRIGGER_OVERFLOW_AND_COMPARE);
+	mutex_unlock(&omap->mutex);
+
+	return 0;
+}
+
+static const struct pwm_ops pwm_omap_dmtimer_ops = {
+	.enable	= pwm_omap_dmtimer_enable,
+	.disable = pwm_omap_dmtimer_disable,
+	.config	= pwm_omap_dmtimer_config,
+	.set_polarity = pwm_omap_dmtimer_set_polarity,
+	.owner = THIS_MODULE,
+};
+
+static int pwm_omap_dmtimer_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct device_node *timer;
+	struct pwm_omap_dmtimer_chip *omap;
+	struct pwm_omap_dmtimer_pdata *pdata;
+	pwm_omap_dmtimer *dm_timer;
+	u32 prescaler;
+	int status;
+
+	pdata = dev_get_platdata(&pdev->dev);
+	if (!pdata) {
+		dev_err(&pdev->dev, "Missing dmtimer platform data\n");
+		return -EINVAL;
+	}
+
+	if (!pdata->request_by_node ||
+	    !pdata->free ||
+	    !pdata->enable ||
+	    !pdata->disable ||
+	    !pdata->get_fclk ||
+	    !pdata->start ||
+	    !pdata->stop ||
+	    !pdata->set_load ||
+	    !pdata->set_match ||
+	    !pdata->set_pwm ||
+	    !pdata->set_prescaler ||
+	    !pdata->write_counter) {
+		dev_err(&pdev->dev, "Incomplete dmtimer pdata structure\n");
+		return -EINVAL;
+	}
+
+	timer = of_parse_phandle(np, "ti,timers", 0);
+	if (!timer)
+		return -ENODEV;
+
+	if (!of_get_property(timer, "ti,timer-pwm", NULL)) {
+		dev_err(&pdev->dev, "Missing ti,timer-pwm capability\n");
+		return -ENODEV;
+	}
+
+	dm_timer = pdata->request_by_node(timer);
+	if (!dm_timer)
+		return -EPROBE_DEFER;
+
+	omap = devm_kzalloc(&pdev->dev, sizeof(*omap), GFP_KERNEL);
+	if (!omap) {
+		omap->pdata->free(dm_timer);
+		return -ENOMEM;
+	}
+
+	omap->pdata = pdata;
+	omap->dm_timer = dm_timer;
+
+	omap->dm_timer_pdev = of_find_device_by_node(timer);
+	if (!omap->dm_timer_pdev) {
+		dev_err(&pdev->dev, "Unable to find timer pdev\n");
+		omap->pdata->free(dm_timer);
+		return -EINVAL;
+	}
+
+	/*
+	 * Ensure that the timer is stopped before we allow PWM core to call
+	 * pwm_enable.
+	 */
+	if (pm_runtime_active(&omap->dm_timer_pdev->dev))
+		omap->pdata->stop(omap->dm_timer);
+
+	/* setup dmtimer prescaler */
+	if (!of_property_read_u32(pdev->dev.of_node, "ti,prescaler",
+				&prescaler))
+		omap->pdata->set_prescaler(omap->dm_timer, prescaler);
+
+	omap->chip.dev = &pdev->dev;
+	omap->chip.ops = &pwm_omap_dmtimer_ops;
+	omap->chip.base = -1;
+	omap->chip.npwm = 1;
+	omap->chip.of_xlate = of_pwm_xlate_with_flags;
+	omap->chip.of_pwm_n_cells = 3;
+
+	mutex_init(&omap->mutex);
+
+	status = pwmchip_add(&omap->chip);
+	if (status < 0) {
+		dev_err(&pdev->dev, "failed to register PWM\n");
+		omap->pdata->free(omap->dm_timer);
+		return status;
+	}
+
+	platform_set_drvdata(pdev, omap);
+
+	return 0;
+}
+
+static int pwm_omap_dmtimer_remove(struct platform_device *pdev)
+{
+	struct pwm_omap_dmtimer_chip *omap = platform_get_drvdata(pdev);
+
+	if (pm_runtime_active(&omap->dm_timer_pdev->dev))
+		omap->pdata->stop(omap->dm_timer);
+
+	omap->pdata->free(omap->dm_timer);
+
+	mutex_destroy(&omap->mutex);
+
+	return pwmchip_remove(&omap->chip);
+}
+
+static const struct of_device_id pwm_omap_dmtimer_of_match[] = {
+	{.compatible = "ti,omap-dmtimer-pwm"},
+	{}
+};
+MODULE_DEVICE_TABLE(of, pwm_omap_dmtimer_of_match);
+
+static struct platform_driver pwm_omap_dmtimer_driver = {
+	.driver = {
+		.name = "omap-dmtimer-pwm",
+		.of_match_table = of_match_ptr(pwm_omap_dmtimer_of_match),
+	},
+	.probe = pwm_omap_dmtimer_probe,
+	.remove	= pwm_omap_dmtimer_remove,
+};
+module_platform_driver(pwm_omap_dmtimer_driver);
+
+MODULE_AUTHOR("Grant Erickson <marathon96@gmail.com>");
+MODULE_AUTHOR("NeilBrown <neilb@suse.de>");
+MODULE_AUTHOR("Neil Armstrong <narmstrong@baylibre.com>");
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("OMAP PWM Driver using Dual-mode Timers");