[PATCH v3 5/5] pwm: omap-dmtimer: Implement .apply callback

Lokesh Vutla
2020-03-12T04:23:26Z

Implement .apply callback and drop the legacy callbacks(enable, disable,
config, set_polarity). In .apply() check for the current hardware status
before changing the pwm configuration.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
---
drivers/pwm/pwm-omap-dmtimer.c | 180 +++++++++++++++++++++++----------
1 file changed, 129 insertions(+), 51 deletions(-)

diff --git a/drivers/pwm/pwm-omap-dmtimer.c b/drivers/pwm/pwm-omap-dmtimer.c
index c56e7256e923..0d31833db2e2 100644
--- a/drivers/pwm/pwm-omap-dmtimer.c
+++ b/drivers/pwm/pwm-omap-dmtimer.c
@@ -26,6 +26,11 @@
* 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>
@@ -46,8 +51,18 @@
#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;
@@ -60,11 +75,22 @@ 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)
{
/*
@@ -82,33 +108,46 @@ static void pwm_omap_dmtimer_start(struct pwm_omap_dmtimer_chip *omap)
omap->pdata->start(omap->dm_timer);
}

-static int pwm_omap_dmtimer_enable(struct pwm_chip *chip,
- struct pwm_device *pwm)
+/**
+ * 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)
{
- struct pwm_omap_dmtimer_chip *omap = to_pwm_omap_dmtimer_chip(chip);
+ u32 status;

- mutex_lock(&omap->mutex);
- omap->pdata->set_pwm(omap->dm_timer,
- pwm_get_polarity(pwm) == PWM_POLARITY_INVERSED,
- true, OMAP_TIMER_TRIGGER_OVERFLOW_AND_COMPARE,
- true);
-
- pwm_omap_dmtimer_start(omap);
- mutex_unlock(&omap->mutex);
+ status = omap->pdata->get_pwm_status(omap->dm_timer);

- return 0;
+ return !!(status & OMAP_TIMER_CTRL_ST);
}

-static void pwm_omap_dmtimer_disable(struct pwm_chip *chip,
- struct pwm_device *pwm)
+/**
+ * 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)
{
- struct pwm_omap_dmtimer_chip *omap = to_pwm_omap_dmtimer_chip(chip);
+ u32 status;

- mutex_lock(&omap->mutex);
- omap->pdata->stop(omap->dm_timer);
- mutex_unlock(&omap->mutex);
+ 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)
@@ -116,30 +155,26 @@ static int pwm_omap_dmtimer_config(struct pwm_chip *chip,
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;
+ struct clk *fclk;

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);
+ 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");
- goto err_einval;
+ return -EINVAL;
}

clk_rate = clk_get_rate(fclk);
if (!clk_rate) {
dev_err(chip->dev, "invalid pmtimer fclk rate\n");
- goto err_einval;
+ return -EINVAL;
}

dev_dbg(chip->dev, "clk rate: %luHz\n", clk_rate);
@@ -167,7 +202,7 @@ static int pwm_omap_dmtimer_config(struct pwm_chip *chip,
dev_info(chip->dev,
"period %d ns too short for clock rate %lu Hz\n",
period_ns, clk_rate);
- goto err_einval;
+ return -EINVAL;
}

if (duty_cycles < 1) {
@@ -199,55 +234,97 @@ static int pwm_omap_dmtimer_config(struct pwm_chip *chip,
dev_dbg(chip->dev, "load value: %#08x (%d), match value: %#08x (%d)\n",
load_value, load_value, match_value, match_value);

- 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)
+/**
+ * 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);

- /*
- * 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, 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 0;
+ return ret;
}

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,
+ .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 device_node *timer;
- struct platform_device *timer_pdev;
- struct pwm_omap_dmtimer_chip *omap;
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;
- u32 v;
+ struct device_node *timer;
int ret = 0;
+ u32 v;

timer = of_parse_phandle(np, "ti,timers", 0);
if (!timer)
@@ -280,6 +357,7 @@ static int pwm_omap_dmtimer_probe(struct platform_device *pdev)
!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");
--
2.23.0