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    Subject[PATCH v4 14/17] pwm: sti: Add PWM Capture call-back
    Date
    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.jones@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 4686ba0..fcc80eb 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 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 - 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));
    +
    + 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);
    + result->period /= effective_ticks;
    +
    + result->duty_cycle = SECS_TO_NANOSECS(high);
    + 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))
    --
    2.9.0
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