linux/drivers/pwm/pwm-omap-dmtimer.c
David Rivshin 922201d129 pwm: omap-dmtimer: Add debug message for effective period and duty cycle
After going through the math and constraints checking to compute load
and match values, it is helpful to know what the resultant period and
duty cycle are.

Signed-off-by: David Rivshin <drivshin@allworx.com>
Acked-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
2016-03-23 17:11:48 +01:00

370 lines
10 KiB
C

/*
* 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
#define DM_TIMER_MAX 0xffffffff
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 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);
}
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);
u32 period_cycles, duty_cycles;
u32 load_value, match_value;
struct clk *fclk;
unsigned long clk_rate;
bool timer_active;
dev_dbg(chip->dev, "requested duty cycle: %d ns, period: %d ns\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");
goto err_einval;
}
clk_rate = clk_get_rate(fclk);
if (!clk_rate) {
dev_err(chip->dev, "invalid pmtimer fclk rate\n");
goto err_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);
goto err_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;
/*
* 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;
err_einval:
mutex_unlock(&omap->mutex);
return -EINVAL;
}
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) {
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");