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 <[email protected]> --- drivers/pwm/pwm-sti.c | 72 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 72 insertions(+) diff --git a/drivers/pwm/pwm-sti.c b/drivers/pwm/pwm-sti.c index 82a69e4..8de9b4a 100644 --- a/drivers/pwm/pwm-sti.c +++ b/drivers/pwm/pwm-sti.c @@ -309,7 +309,79 @@ 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, + int channel, char *buf) +{ + struct sti_pwm_chip *pc = to_sti_pwmchip(chip); + struct sti_pwm_compat_data *cdata = pc->cdata; + struct sti_cpt_data *d = pc->cpt_data[channel]; + struct device *dev = pc->dev; + unsigned int f, dc; + unsigned int high, low; + bool level; + int ret; + + if (channel > cdata->cpt_num_chan - 1) { + dev_err(dev, "Channel %d is not valid\n", channel); + return -EINVAL; + } + + mutex_lock(&d->lock); + + /* Prepare capture measurement */ + d->index = 0; + regmap_write(pc->regmap, PWM_CPT_EDGE(channel), CPT_EDGE_RISING); + regmap_field_write(pc->pwm_cpt_int_en, BIT(channel)); + ret = wait_event_interruptible_timeout(d->wait, d->index > 1, HZ); + + /* + * In case we woke up for another reason than completion + * make sure to disable the capture. + */ + regmap_write(pc->regmap, PWM_CPT_EDGE(channel), CPT_EDGE_DISABLED); + + if (ret == -ERESTARTSYS) + goto out; + + switch (d->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 + * level of the supposed constant signal is reported + * using duty cycle min and max values. + */ + level = gpio_get_value(d->gpio); + + ret = sprintf(buf, "0:%u\n", level ? CPT_DC_MAX : 0); + break; + case 2: + /* We have evertying we need */ + high = d->snapshot[1] - d->snapshot[0]; + low = d->snapshot[2] - d->snapshot[1]; + + /* Calculate frequency in Hz */ + f = clk_get_rate(pc->cpt_clk) / (1 * (high + low)); + + /* Calculate the duty cycle */ + dc = CPT_DC_MAX * high / (high + low); + + ret = sprintf(buf, "%u:%u\n", f, dc); + default: + dev_err(dev, "Internal error\n"); + } + +out: + mutex_unlock(&d->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, -- 1.9.1
