pwm: sti: Add PWM capture callback

Once a PWM capture has been initiated, the capture call enables a rising
edge detection interrupt, 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 returns a structure filled out
with the capture data.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

diff --git a/drivers/pwm/pwm-sti.c b/drivers/pwm/pwm-sti.c
index bd753fbad08ad8ad5efe620f0e7403379b67f0b1..95014f57a9c6d1d3ad7eae86b4f001777efe2e78 100644 (file)
--- a/drivers/pwm/pwm-sti.c
+++ b/drivers/pwm/pwm-sti.c
@@ -305,7 +305,90 @@ 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 long timeout)
+{
+       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) {
+               dev_err(dev, "device %u is not valid\n", pwm->hwpwm);
+               return -EINVAL;
+       }
+
+       mutex_lock(&ddata->lock);
+       ddata->index = 0;
+
+       /* Prepare capture measurement */
+       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 %u: %d\n",
+                       pwm->hwpwm, ret);
+               goto out;
+       }
+
+       ret = wait_event_interruptible_timeout(ddata->wait, ddata->index > 1,
+                                              msecs_to_jiffies(timeout));
+
+       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 1 Hz
+                *  - 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 = (high + low) * NSEC_PER_SEC;
+               result->period /= effective_ticks;
+
+               result->duty_cycle = high * NSEC_PER_SEC;
+               result->duty_cycle /= effective_ticks;
+
+               break;
+
+       default:
+               dev_err(dev, "internal error\n");
+               break;
+       }
+
+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))