Once a PWM Capture has been initiated, the capture call
enables a rising edge detection IRQ, then waits. Once each
of the 3 phase changes have been recorded the thread then
wakes. The remaining part of the call carries out the
relevant calculations and passes back a formatted string to
the caller.
Signed-off-by: Lee Jones <lee.jo...@linaro.org>
---
drivers/pwm/pwm-sti.c | 88 +++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 88 insertions(+)
diff --git a/drivers/pwm/pwm-sti.c b/drivers/pwm/pwm-sti.c
index 2230afb..cecb6d4 100644
--- a/drivers/pwm/pwm-sti.c
+++ b/drivers/pwm/pwm-sti.c
@@ -24,6 +24,8 @@
#include <linux/time.h>
#include <linux/wait.h>
+#define SECS_TO_NANOSECS(x) ((x) * 1000 * 1000 * 1000)
+
#define PWM_OUT_VAL(x) (0x00 + (4 * (x))) /* Device's Duty Cycle register */
#define PWM_CPT_VAL(x) (0x10 + (4 * (x))) /* Capture value */
#define PWM_CPT_EDGE(x) (0x30 + (4 * (x))) /* Edge to capture on */
@@ -305,7 +307,88 @@ static void sti_pwm_free(struct pwm_chip *chip, struct
pwm_device *pwm)
clear_bit(pwm->hwpwm, &pc->configured);
}
+static int sti_pwm_capture(struct pwm_chip *chip, struct pwm_device *pwm,
+ struct pwm_capture *result, unsigned int timeout_ms)
+{
+ struct sti_pwm_chip *pc = to_sti_pwmchip(chip);
+ struct sti_pwm_compat_data *cdata = pc->cdata;
+ struct sti_cpt_ddata *ddata = pwm_get_chip_data(pwm);
+ struct device *dev = pc->dev;
+ unsigned int effective_ticks;
+ unsigned long long high, low;
+ int ret;
+
+ if (pwm->hwpwm > cdata->cpt_num_devs - 1) {
+ dev_err(dev, "Device %d is not valid\n", pwm->hwpwm);
+ return -EINVAL;
+ }
+
+ mutex_lock(&ddata->lock);
+
+ /* Prepare capture measurement */
+ ddata->index = 0;
+ regmap_write(pc->regmap, PWM_CPT_EDGE(pwm->hwpwm), CPT_EDGE_RISING);
+ regmap_field_write(pc->pwm_cpt_int_en, BIT(pwm->hwpwm));
+
+ /* Enable capture */
+ ret = regmap_field_write(pc->pwm_cpt_en, 1);
+ if (ret) {
+ dev_err(dev, "failed to enable PWM capture %d\n", pwm->hwpwm);
+ goto out;
+ }
+
+ ret = wait_event_interruptible_timeout(ddata->wait,
+ ddata->index > 1,
+ msecs_to_jiffies(timeout_ms));
+
+ regmap_write(pc->regmap, PWM_CPT_EDGE(pwm->hwpwm), CPT_EDGE_DISABLED);
+
+ if (ret == -ERESTARTSYS)
+ goto out;
+
+ switch (ddata->index) {
+ case 0:
+ case 1:
+ /*
+ * Getting here could mean :
+ * - input signal is constant of less than 1Hz
+ * - there is no input signal at all
+ *
+ * In such case the frequency is rounded down to 0
+ */
+
+ result->period = 0;
+ result->duty_cycle = 0;
+
+ break;
+ case 2:
+ /* We have everying we need */
+ high = ddata->snapshot[1] - ddata->snapshot[0];
+ low = ddata->snapshot[2] - ddata->snapshot[1];
+
+ effective_ticks = clk_get_rate(pc->cpt_clk);
+
+ result->period = SECS_TO_NANOSECS(high + low);
+ do_div(result->period, effective_ticks);
+
+ result->duty_cycle = SECS_TO_NANOSECS(high);
+ do_div(result->duty_cycle, effective_ticks);
+
+ break;
+ default:
+ dev_err(dev, "Internal error\n");
+ }
+
+out:
+ /* Disable capture */
+ regmap_field_write(pc->pwm_cpt_en, 0);
+
+ mutex_unlock(&ddata->lock);
+ return ret;
+}
+
static const struct pwm_ops sti_pwm_ops = {
+ .capture = sti_pwm_capture,
.config = sti_pwm_config,
.enable = sti_pwm_enable,
.disable = sti_pwm_disable,
@@ -418,6 +501,11 @@ static int sti_pwm_probe_dt(struct sti_pwm_chip *pc)
if (IS_ERR(pc->pwm_out_en))
return PTR_ERR(pc->pwm_out_en);
+ pc->pwm_cpt_en = devm_regmap_field_alloc(dev, pc->regmap,
+ reg_fields[PWM_CPT_EN]);
+ if (IS_ERR(pc->pwm_cpt_en))
+ return PTR_ERR(pc->pwm_cpt_en);
+
pc->pwm_cpt_int_en = devm_regmap_field_alloc(dev, pc->regmap,
reg_fields[PWM_CPT_INT_EN]);
if (IS_ERR(pc->pwm_cpt_int_en))
--
2.8.0
