Hi Theirry,
If there are no more comments can this patch be applied?
Thanks,
Jon
On 15-06-15 02:21 PM, Jonathan Richardson wrote:
> Update the driver so that settings are applied in accordance with the
> most recent version of the hardware spec. The revised sequence clears
> the trigger bit, waits 400ns, writes settings, sets the trigger bit,
> and waits another 400ns. This corrects an issue where occasionally a
> requested change was not properly reflected in the PWM output.
>
> Reviewed-by: Arun Ramamurthy <arunr...@broadcom.com>
> Reviewed-by: Scott Branden <sbran...@broadcom.com>
> Tested-by: Scott Branden <sbran...@broadcom.com>
> Reviewed-by: Tim Kryger <tim.kry...@gmail.com>
> Signed-off-by: Jonathan Richardson <jonat...@broadcom.com>
> ---
> drivers/pwm/pwm-bcm-kona.c | 47
> +++++++++++++++++++++++++++++++++++---------
> 1 file changed, 38 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/pwm/pwm-bcm-kona.c b/drivers/pwm/pwm-bcm-kona.c
> index 7af8fea..9b1d397 100644
> --- a/drivers/pwm/pwm-bcm-kona.c
> +++ b/drivers/pwm/pwm-bcm-kona.c
> @@ -76,19 +76,36 @@ static inline struct kona_pwmc *to_kona_pwmc(struct
> pwm_chip *_chip)
> return container_of(_chip, struct kona_pwmc, chip);
> }
>
> -static void kona_pwmc_apply_settings(struct kona_pwmc *kp, unsigned int chan)
> +/*
> + * Clear trigger bit but set smooth bit to maintain old output.
> + */
> +static void kona_pwmc_prepare_for_settings(struct kona_pwmc *kp,
> + unsigned int chan)
> {
> unsigned int value = readl(kp->base + PWM_CONTROL_OFFSET);
>
> - /* Clear trigger bit but set smooth bit to maintain old output */
> value |= 1 << PWM_CONTROL_SMOOTH_SHIFT(chan);
> value &= ~(1 << PWM_CONTROL_TRIGGER_SHIFT(chan));
> writel(value, kp->base + PWM_CONTROL_OFFSET);
>
> + /*
> + * There must be a min 400ns delay between clearing trigger and setting
> + * it. Failing to do this may result in no PWM signal.
> + */
> + ndelay(400);
> +}
> +
> +static void kona_pwmc_apply_settings(struct kona_pwmc *kp, unsigned int chan)
> +{
> + unsigned int value = readl(kp->base + PWM_CONTROL_OFFSET);
> +
> /* Set trigger bit and clear smooth bit to apply new settings */
> value &= ~(1 << PWM_CONTROL_SMOOTH_SHIFT(chan));
> value |= 1 << PWM_CONTROL_TRIGGER_SHIFT(chan);
> writel(value, kp->base + PWM_CONTROL_OFFSET);
> +
> + /* Trigger bit must be held high for at least 400 ns. */
> + ndelay(400);
> }
>
> static int kona_pwmc_config(struct pwm_chip *chip, struct pwm_device *pwm,
> @@ -133,8 +150,14 @@ static int kona_pwmc_config(struct pwm_chip *chip,
> struct pwm_device *pwm,
> return -EINVAL;
> }
>
> - /* If the PWM channel is enabled, write the settings to the HW */
> + /*
> + * Don't apply settings if disabled. The period and duty cycle are
> + * always calculated above to ensure the new values are
> + * validated immediately instead of on enable.
> + */
> if (test_bit(PWMF_ENABLED, &pwm->flags)) {
> + kona_pwmc_prepare_for_settings(kp, chan);
> +
> value = readl(kp->base + PRESCALE_OFFSET);
> value &= ~PRESCALE_MASK(chan);
> value |= prescale << PRESCALE_SHIFT(chan);
> @@ -164,6 +187,8 @@ static int kona_pwmc_set_polarity(struct pwm_chip *chip,
> struct pwm_device *pwm,
> return ret;
> }
>
> + kona_pwmc_prepare_for_settings(kp, chan);
> +
> value = readl(kp->base + PWM_CONTROL_OFFSET);
>
> if (polarity == PWM_POLARITY_NORMAL)
> @@ -175,9 +200,6 @@ static int kona_pwmc_set_polarity(struct pwm_chip *chip,
> struct pwm_device *pwm,
>
> kona_pwmc_apply_settings(kp, chan);
>
> - /* Wait for waveform to settle before gating off the clock */
> - ndelay(400);
> -
> clk_disable_unprepare(kp->clk);
>
> return 0;
> @@ -207,13 +229,20 @@ static void kona_pwmc_disable(struct pwm_chip *chip,
> struct pwm_device *pwm)
> {
> struct kona_pwmc *kp = to_kona_pwmc(chip);
> unsigned int chan = pwm->hwpwm;
> + unsigned int value;
> +
> + kona_pwmc_prepare_for_settings(kp, chan);
>
> /* Simulate a disable by configuring for zero duty */
> writel(0, kp->base + DUTY_CYCLE_HIGH_OFFSET(chan));
> - kona_pwmc_apply_settings(kp, chan);
> + writel(0, kp->base + PERIOD_COUNT_OFFSET(chan));
>
> - /* Wait for waveform to settle before gating off the clock */
> - ndelay(400);
> + /* Set prescale to 0 for this channel */
> + value = readl(kp->base + PRESCALE_OFFSET);
> + value &= ~PRESCALE_MASK(chan);
> + writel(value, kp->base + PRESCALE_OFFSET);
> +
> + kona_pwmc_apply_settings(kp, chan);
>
> clk_disable_unprepare(kp->clk);
> }
>
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