Implement .get_state to read-out the current hardware state.
The hardware readout may return slightly different values than those
that were set in apply due to the limited range of possible prescale and
counter register values.
Also note that although the datasheet mentions 200 Hz as default
frequency when using the internal 25 MHz oscillator, the calculated
period from the default prescaler register setting of 30 is 5079040ns.
Signed-off-by: Clemens Gruber <[email protected]>
---
Changes since v8:
- As we left the math in apply as-is, use DIV_ROUND_DOWN in get_state
Changes since v7:
- Always return enabled=true for channels except "all LEDs" channel
- Use DIV_ROUND_UP in .get_state
Changes since v6:
- Added a comment regarding the division (Suggested by Uwe)
- Rebased
drivers/pwm/pwm-pca9685.c | 36 ++++++++++++++++++++++++++++++++++++
1 file changed, 36 insertions(+)
diff --git a/drivers/pwm/pwm-pca9685.c b/drivers/pwm/pwm-pca9685.c
index ea19d72e5c34..aa48c45bd294 100644
--- a/drivers/pwm/pwm-pca9685.c
+++ b/drivers/pwm/pwm-pca9685.c
@@ -331,6 +331,41 @@ static int pca9685_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
return 0;
}
+static void pca9685_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+ struct pwm_state *state)
+{
+ struct pca9685 *pca = to_pca(chip);
+ unsigned long long duty;
+ unsigned int val = 0;
+
+ /* Calculate (chip-wide) period from prescale value */
+ regmap_read(pca->regmap, PCA9685_PRESCALE, &val);
+ /*
+ * PCA9685_OSC_CLOCK_MHZ is 25, i.e. an integer divider of 1000.
+ * The following calculation is therefore only a multiplication
+ * and we are not losing precision.
+ */
+ state->period = (PCA9685_COUNTER_RANGE * 1000 / PCA9685_OSC_CLOCK_MHZ) *
+ (val + 1);
+
+ /* The (per-channel) polarity is fixed */
+ state->polarity = PWM_POLARITY_NORMAL;
+
+ if (pwm->hwpwm >= PCA9685_MAXCHAN) {
+ /*
+ * The "all LEDs" channel does not support HW readout
+ * Return 0 and disabled for backwards compatibility
+ */
+ state->duty_cycle = 0;
+ state->enabled = false;
+ return;
+ }
+
+ state->enabled = true;
+ duty = pca9685_pwm_get_duty(pca, pwm->hwpwm);
+ state->duty_cycle = DIV_ROUND_DOWN_ULL(duty * state->period, PCA9685_COUNTER_RANGE);
+}
+
static int pca9685_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
{
struct pca9685 *pca = to_pca(chip);
@@ -353,6 +388,7 @@ static void pca9685_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
static const struct pwm_ops pca9685_pwm_ops = {
.apply = pca9685_pwm_apply,
+ .get_state = pca9685_pwm_get_state,
.request = pca9685_pwm_request,
.free = pca9685_pwm_free,
.owner = THIS_MODULE,
--
2.31.1
Hello,
On Thu, Apr 15, 2021 at 02:14:49PM +0200, Clemens Gruber wrote:
> Implement .get_state to read-out the current hardware state.
>
> The hardware readout may return slightly different values than those
> that were set in apply due to the limited range of possible prescale and
> counter register values.
>
> Also note that although the datasheet mentions 200 Hz as default
> frequency when using the internal 25 MHz oscillator, the calculated
> period from the default prescaler register setting of 30 is 5079040ns.
>
> Signed-off-by: Clemens Gruber <[email protected]>
> ---
> Changes since v8:
> - As we left the math in apply as-is, use DIV_ROUND_DOWN in get_state
I first thought this was wrong, because .apply uses ROUND_CLOSEST for
period and ROUND_UP for duty. But as the calculation for period is exact
this doesn't matter and round-down is indeed correct here.
Reviewed-by: Uwe Kleine-K?nig <[email protected]>
Thanks
Uwe
--
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