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>

1 files changed, 327 insertions, 0 deletions

diff --git a/drivers/pwm/pwm-omap-dmtimer.c b/drivers/pwm/pwm-omap-dmtimer.c
new file mode 100644
index 000000000000..c453b3360605
--- /dev/null
+++ b/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");