linux-kernel - Re: [PATCH 11/14] pwm: meson: read the full hardware state in meson_pwm_get

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Date:   Mon, 27 May 2019 14:31:00 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        linux-amlogic@...ts.infradead.org, linux-pwm@...r.kernel.org,
        thierry.reding@...il.com, u.kleine-koenig@...gutronix.de
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 11/14] pwm: meson: read the full hardware state in
 meson_pwm_get_state()

On 25/05/2019 20:11, Martin Blumenstingl wrote:
> Update the meson_pwm_get_state() implementation to take care of all
> information in the registers instead of only reading the "enabled"
> state.
> 
> The PWM output is only enabled if two conditions are met:
> 1. the per-channel clock is enabled
> 2. the PWM output is enabled
> 
> Calculate the PWM period and duty cycle using the reverse formula which
> we already have in meson_pwm_calc() and update struct pwm_state with the
> results.
> 
> As result of this /sys/kernel/debug/pwm now shows the PWM state set by
> the bootloader (or firmware) after booting Linux.
> 
> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
> ---
>  drivers/pwm/pwm-meson.c | 52 ++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 49 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-meson.c b/drivers/pwm/pwm-meson.c
> index 9afa1e5aaebf..010212166d5d 100644
> --- a/drivers/pwm/pwm-meson.c
> +++ b/drivers/pwm/pwm-meson.c
> @@ -287,19 +287,65 @@ static int meson_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
>  	return 0;
>  }
>  
> +static unsigned int meson_pwm_cnt_to_ns(struct pwm_chip *chip,
> +					struct pwm_device *pwm, u32 cnt)
> +{
> +	struct meson_pwm *meson = to_meson_pwm(chip);
> +	struct meson_pwm_channel *channel;
> +	unsigned long fin_freq;
> +	u32 fin_ns;
> +
> +	/* to_meson_pwm() can only be used after .get_state() is called */
> +	channel = &meson->channels[pwm->hwpwm];
> +
> +	fin_freq = clk_get_rate(channel->clk);
> +	if (fin_freq == 0)
> +		return 0;
> +
> +	fin_ns = div_u64(NSEC_PER_SEC, fin_freq);
> +
> +	return cnt * fin_ns * (channel->pre_div + 1);
> +}
> +
>  static void meson_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
>  				struct pwm_state *state)
>  {
>  	struct meson_pwm *meson = to_meson_pwm(chip);
> -	u32 value, mask;
> +	struct meson_pwm_channel_data *channel_data;
> +	struct meson_pwm_channel *channel;
> +	u32 value, tmp;
>  
>  	if (!state)
>  		return;
>  
> -	mask = meson_pwm_per_channel_data[pwm->hwpwm].pwm_en_mask;
> +	channel = &meson->channels[pwm->hwpwm];
> +	channel_data = &meson_pwm_per_channel_data[pwm->hwpwm];
>  
>  	value = readl(meson->base + REG_MISC_AB);
> -	state->enabled = (value & mask) != 0;
> +
> +	tmp = channel_data->pwm_en_mask | channel_data->clk_en_mask;
> +	state->enabled = (value & tmp) == tmp;
> +
> +	tmp = value >> channel_data->clk_div_shift;
> +	channel->pre_div = FIELD_GET(MISC_CLK_DIV_MASK, tmp);
> +
> +	value = readl(meson->base + channel_data->reg_offset);
> +
> +	channel->lo = FIELD_GET(PWM_LOW_MASK, value);
> +	channel->hi = FIELD_GET(PWM_HIGH_MASK, value);
> +
> +	if (channel->lo == 0) {
> +		state->period = meson_pwm_cnt_to_ns(chip, pwm, channel->hi);
> +		state->duty_cycle = state->period;
> +	} else if (channel->lo >= channel->hi) {
> +		state->period = meson_pwm_cnt_to_ns(chip, pwm,
> +						    channel->lo + channel->hi);
> +		state->duty_cycle = meson_pwm_cnt_to_ns(chip, pwm,
> +							channel->hi);
> +	} else {
> +		state->period = 0;
> +		state->duty_cycle = 0;
> +	}
>  }
>  
>  static const struct pwm_ops meson_pwm_ops = {
> 

Thanks for that !!!

Reviewed-by: Neil Armstrong <narmstrong@...libre.com>