diff options
Diffstat (limited to 'drivers/pwm/pwm-omap-dmtimer.c')
| -rw-r--r-- | drivers/pwm/pwm-omap-dmtimer.c | 482 |
1 files changed, 482 insertions, 0 deletions
diff --git a/drivers/pwm/pwm-omap-dmtimer.c b/drivers/pwm/pwm-omap-dmtimer.c new file mode 100644 index 000000000..fa800fcf3 --- /dev/null +++ b/drivers/pwm/pwm-omap-dmtimer.c @@ -0,0 +1,482 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * 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 + * + * Description: + * This file is the core OMAP support for the generic, Linux + * PWM driver / controller, using the OMAP's dual-mode timers + * with a timer counter that goes up. When it overflows it gets + * reloaded with the load value and the pwm output goes up. + * When counter matches with match register, the output goes down. + * Reference Manual: https://www.ti.com/lit/ug/spruh73q/spruh73q.pdf + * + * Limitations: + * - When PWM is stopped, timer counter gets stopped immediately. This + * doesn't allow the current PWM period to complete and stops abruptly. + * - When PWM is running and changing both duty cycle and period, + * we cannot prevent in software that the output might produce + * a period with mixed settings. Especially when period/duty_cyle + * is updated while the pwm pin is high, current pwm period/duty_cycle + * can get updated as below based on the current timer counter: + * - period for current cycle = current_period + new period + * - duty_cycle for current period = current period + new duty_cycle. + * - PWM OMAP DM timer cannot change the polarity when pwm is active. When + * user requests a change in polarity when in active state: + * - PWM is stopped abruptly(without completing the current cycle) + * - Polarity is changed + * - A fresh cycle is started. + */ + +#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 <clocksource/timer-ti-dm.h> +#include <linux/platform_data/dmtimer-omap.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 +#define DM_TIMER_MAX 0xffffffff + +/** + * struct pwm_omap_dmtimer_chip - Structure representing a pwm chip + * corresponding to omap dmtimer. + * @chip: PWM chip structure representing PWM controller + * @mutex: Mutex to protect pwm apply state + * @dm_timer: Pointer to omap dm timer. + * @pdata: Pointer to omap dm timer ops. + * @dm_timer_pdev: Pointer to omap dm timer platform device + */ +struct pwm_omap_dmtimer_chip { + struct pwm_chip chip; + /* Mutex to protect pwm apply state */ + struct mutex mutex; + struct omap_dm_timer *dm_timer; + const struct omap_dm_timer_ops *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); +} + +/** + * pwm_omap_dmtimer_get_clock_cycles() - Get clock cycles in a time frame + * @clk_rate: pwm timer clock rate + * @ns: time frame in nano seconds. + * + * Return number of clock cycles in a given period(ins ns). + */ +static u32 pwm_omap_dmtimer_get_clock_cycles(unsigned long clk_rate, int ns) +{ + return DIV_ROUND_CLOSEST_ULL((u64)clk_rate * ns, NSEC_PER_SEC); +} + +/** + * pwm_omap_dmtimer_start() - Start the pwm omap dm timer in pwm mode + * @omap: Pointer to pwm omap dm timer chip + */ +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); +} + +/** + * pwm_omap_dmtimer_is_enabled() - Detect if the pwm is enabled. + * @omap: Pointer to pwm omap dm timer chip + * + * Return true if pwm is enabled else false. + */ +static bool pwm_omap_dmtimer_is_enabled(struct pwm_omap_dmtimer_chip *omap) +{ + u32 status; + + status = omap->pdata->get_pwm_status(omap->dm_timer); + + return !!(status & OMAP_TIMER_CTRL_ST); +} + +/** + * pwm_omap_dmtimer_polarity() - Detect the polarity of pwm. + * @omap: Pointer to pwm omap dm timer chip + * + * Return the polarity of pwm. + */ +static int pwm_omap_dmtimer_polarity(struct pwm_omap_dmtimer_chip *omap) +{ + u32 status; + + status = omap->pdata->get_pwm_status(omap->dm_timer); + + return !!(status & OMAP_TIMER_CTRL_SCPWM); +} + +/** + * pwm_omap_dmtimer_config() - Update the configuration of pwm omap dm timer + * @chip: Pointer to PWM controller + * @pwm: Pointer to PWM channel + * @duty_ns: New duty cycle in nano seconds + * @period_ns: New period in nano seconds + * + * Return 0 if successfully changed the period/duty_cycle else appropriate + * error. + */ +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); + u32 period_cycles, duty_cycles; + u32 load_value, match_value; + unsigned long clk_rate; + struct clk *fclk; + + dev_dbg(chip->dev, "requested duty cycle: %d ns, period: %d ns\n", + duty_ns, period_ns); + + if (duty_ns == pwm_get_duty_cycle(pwm) && + period_ns == pwm_get_period(pwm)) + return 0; + + fclk = omap->pdata->get_fclk(omap->dm_timer); + if (!fclk) { + dev_err(chip->dev, "invalid pmtimer fclk\n"); + return -EINVAL; + } + + clk_rate = clk_get_rate(fclk); + if (!clk_rate) { + dev_err(chip->dev, "invalid pmtimer fclk rate\n"); + 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 + * period time and the match value determines the duty time. + * + * The period lasts for (DM_TIMER_MAX-load_value+1) clock cycles. + * Similarly, the active time lasts (match_value-load_value+1) cycles. + * The non-active time is the remainder: (DM_TIMER_MAX-match_value) + * clock cycles. + * + * NOTE: It is required that: load_value <= match_value < DM_TIMER_MAX + * + * References: + * OMAP4430/60/70 TRM sections 22.2.4.10 and 22.2.4.11 + * AM335x Sitara TRM sections 20.1.3.5 and 20.1.3.6 + */ + period_cycles = pwm_omap_dmtimer_get_clock_cycles(clk_rate, period_ns); + duty_cycles = pwm_omap_dmtimer_get_clock_cycles(clk_rate, duty_ns); + + if (period_cycles < 2) { + dev_info(chip->dev, + "period %d ns too short for clock rate %lu Hz\n", + period_ns, clk_rate); + return -EINVAL; + } + + if (duty_cycles < 1) { + dev_dbg(chip->dev, + "duty cycle %d ns is too short for clock rate %lu Hz\n", + duty_ns, clk_rate); + dev_dbg(chip->dev, "using minimum of 1 clock cycle\n"); + duty_cycles = 1; + } else if (duty_cycles >= period_cycles) { + dev_dbg(chip->dev, + "duty cycle %d ns is too long for period %d ns at clock rate %lu Hz\n", + duty_ns, period_ns, clk_rate); + dev_dbg(chip->dev, "using maximum of 1 clock cycle less than period\n"); + duty_cycles = period_cycles - 1; + } + + dev_dbg(chip->dev, "effective duty cycle: %lld ns, period: %lld ns\n", + DIV_ROUND_CLOSEST_ULL((u64)NSEC_PER_SEC * duty_cycles, + clk_rate), + DIV_ROUND_CLOSEST_ULL((u64)NSEC_PER_SEC * period_cycles, + clk_rate)); + + load_value = (DM_TIMER_MAX - period_cycles) + 1; + match_value = load_value + duty_cycles - 1; + + omap->pdata->set_load(omap->dm_timer, 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); + + return 0; +} + +/** + * pwm_omap_dmtimer_set_polarity() - Changes the polarity of the pwm dm timer. + * @chip: Pointer to PWM controller + * @pwm: Pointer to PWM channel + * @polarity: New pwm polarity to be set + */ +static void 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); + bool enabled; + + /* Disable the PWM before changing the polarity. */ + enabled = pwm_omap_dmtimer_is_enabled(omap); + if (enabled) + omap->pdata->stop(omap->dm_timer); + + omap->pdata->set_pwm(omap->dm_timer, + polarity == PWM_POLARITY_INVERSED, + true, OMAP_TIMER_TRIGGER_OVERFLOW_AND_COMPARE, + true); + + if (enabled) + pwm_omap_dmtimer_start(omap); +} + +/** + * pwm_omap_dmtimer_apply() - Changes the state of the pwm omap dm timer. + * @chip: Pointer to PWM controller + * @pwm: Pointer to PWM channel + * @state: New state to apply + * + * Return 0 if successfully changed the state else appropriate error. + */ +static int pwm_omap_dmtimer_apply(struct pwm_chip *chip, + struct pwm_device *pwm, + const struct pwm_state *state) +{ + struct pwm_omap_dmtimer_chip *omap = to_pwm_omap_dmtimer_chip(chip); + int ret = 0; + + mutex_lock(&omap->mutex); + + if (pwm_omap_dmtimer_is_enabled(omap) && !state->enabled) { + omap->pdata->stop(omap->dm_timer); + goto unlock_mutex; + } + + if (pwm_omap_dmtimer_polarity(omap) != state->polarity) + pwm_omap_dmtimer_set_polarity(chip, pwm, state->polarity); + + ret = pwm_omap_dmtimer_config(chip, pwm, state->duty_cycle, + state->period); + if (ret) + goto unlock_mutex; + + if (!pwm_omap_dmtimer_is_enabled(omap) && state->enabled) { + omap->pdata->set_pwm(omap->dm_timer, + state->polarity == PWM_POLARITY_INVERSED, + true, + OMAP_TIMER_TRIGGER_OVERFLOW_AND_COMPARE, + true); + pwm_omap_dmtimer_start(omap); + } + +unlock_mutex: + mutex_unlock(&omap->mutex); + + return ret; +} + +static const struct pwm_ops pwm_omap_dmtimer_ops = { + .apply = pwm_omap_dmtimer_apply, + .owner = THIS_MODULE, +}; + +static int pwm_omap_dmtimer_probe(struct platform_device *pdev) +{ + struct device_node *np = pdev->dev.of_node; + struct dmtimer_platform_data *timer_pdata; + const struct omap_dm_timer_ops *pdata; + struct platform_device *timer_pdev; + struct pwm_omap_dmtimer_chip *omap; + struct omap_dm_timer *dm_timer; + struct device_node *timer; + int ret = 0; + u32 v; + + timer = of_parse_phandle(np, "ti,timers", 0); + if (!timer) + return -ENODEV; + + timer_pdev = of_find_device_by_node(timer); + if (!timer_pdev) { + dev_err(&pdev->dev, "Unable to find Timer pdev\n"); + ret = -ENODEV; + goto err_find_timer_pdev; + } + + timer_pdata = dev_get_platdata(&timer_pdev->dev); + if (!timer_pdata) { + dev_dbg(&pdev->dev, + "dmtimer pdata structure NULL, deferring probe\n"); + ret = -EPROBE_DEFER; + goto err_platdata; + } + + pdata = timer_pdata->timer_ops; + + if (!pdata || !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->get_pwm_status || + !pdata->set_prescaler || + !pdata->write_counter) { + dev_err(&pdev->dev, "Incomplete dmtimer pdata structure\n"); + ret = -EINVAL; + goto err_platdata; + } + + if (!of_get_property(timer, "ti,timer-pwm", NULL)) { + dev_err(&pdev->dev, "Missing ti,timer-pwm capability\n"); + ret = -ENODEV; + goto err_timer_property; + } + + dm_timer = pdata->request_by_node(timer); + if (!dm_timer) { + ret = -EPROBE_DEFER; + goto err_request_timer; + } + + omap = devm_kzalloc(&pdev->dev, sizeof(*omap), GFP_KERNEL); + if (!omap) { + ret = -ENOMEM; + goto err_alloc_omap; + } + + omap->pdata = pdata; + omap->dm_timer = dm_timer; + omap->dm_timer_pdev = timer_pdev; + + /* + * 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); + + if (!of_property_read_u32(pdev->dev.of_node, "ti,prescaler", &v)) + omap->pdata->set_prescaler(omap->dm_timer, v); + + /* setup dmtimer clock source */ + if (!of_property_read_u32(pdev->dev.of_node, "ti,clock-source", &v)) + omap->pdata->set_source(omap->dm_timer, v); + + omap->chip.dev = &pdev->dev; + omap->chip.ops = &pwm_omap_dmtimer_ops; + omap->chip.npwm = 1; + + mutex_init(&omap->mutex); + + ret = pwmchip_add(&omap->chip); + if (ret < 0) { + dev_err(&pdev->dev, "failed to register PWM\n"); + goto err_pwmchip_add; + } + + of_node_put(timer); + + platform_set_drvdata(pdev, omap); + + return 0; + +err_pwmchip_add: + + /* + * *omap is allocated using devm_kzalloc, + * so no free necessary here + */ +err_alloc_omap: + + pdata->free(dm_timer); +err_request_timer: + +err_timer_property: +err_platdata: + + put_device(&timer_pdev->dev); +err_find_timer_pdev: + + of_node_put(timer); + + return ret; +} + +static int pwm_omap_dmtimer_remove(struct platform_device *pdev) +{ + struct pwm_omap_dmtimer_chip *omap = platform_get_drvdata(pdev); + + pwmchip_remove(&omap->chip); + + if (pm_runtime_active(&omap->dm_timer_pdev->dev)) + omap->pdata->stop(omap->dm_timer); + + omap->pdata->free(omap->dm_timer); + + put_device(&omap->dm_timer_pdev->dev); + + mutex_destroy(&omap->mutex); + + return 0; +} + +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"); |