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Date: Mon, 24 Feb 2020 10:07:06 +0100
From: Uwe Kleine-König
<u.kleine-koenig@...gutronix.de>
To: Lokesh Vutla <lokeshvutla@...com>
Cc: Thierry Reding <thierry.reding@...il.com>,
Tony Lindgren <tony@...mide.com>,
Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
linux-kernel@...r.kernel.org, linux-pwm@...r.kernel.org,
Sekhar Nori <nsekhar@...com>
Subject: Re: [PATCH 4/4] pwm: omap-dmtimer: Implement .apply callback
On Mon, Feb 24, 2020 at 10:51:35AM +0530, Lokesh Vutla wrote:
> Implement .apply callback and drop the legacy callbacks(enable, disable,
> config, set_polarity).
>
> Signed-off-by: Lokesh Vutla <lokeshvutla@...com>
> ---
> drivers/pwm/pwm-omap-dmtimer.c | 141 +++++++++++++++++++--------------
> 1 file changed, 80 insertions(+), 61 deletions(-)
>
> diff --git a/drivers/pwm/pwm-omap-dmtimer.c b/drivers/pwm/pwm-omap-dmtimer.c
> index 58c61559e72f..aeda4ab12385 100644
> --- a/drivers/pwm/pwm-omap-dmtimer.c
> +++ b/drivers/pwm/pwm-omap-dmtimer.c
> @@ -31,8 +31,18 @@
> #define DM_TIMER_LOAD_MIN 0xfffffffe
> #define DM_TIMER_MAX 0xffffffff
>
> +/**
> + * struct pwm_omap_dmtimer_chip - Structure representing a pwm chip
> + * corresponding to omap dmtimer.
> + * @chip: PWM chip structure representing PWM controller
> + * @mutex: Mutex to protect pwm apply state
> + * @dm_timer: Pointer to omap dm timer.
> + * @pdata: Pointer to omap dm timer ops.
> + * dm_timer_pdev: Pointer to omap dm timer platform device
> + */
> struct pwm_omap_dmtimer_chip {
> struct pwm_chip chip;
> + /* Mutex to protect pwm apply state */
> struct mutex mutex;
> struct omap_dm_timer *dm_timer;
> const struct omap_dm_timer_ops *pdata;
> @@ -45,11 +55,22 @@ to_pwm_omap_dmtimer_chip(struct pwm_chip *chip)
> return container_of(chip, struct pwm_omap_dmtimer_chip, chip);
> }
>
> +/**
> + * pwm_omap_dmtimer_get_clock_cycles() - Get clock cycles in a time frame
> + * @clk_rate: pwm timer clock rate
> + * @ns: time frame in nano seconds.
> + *
> + * Return number of clock cycles in a given period(ins ns).
> + */
> static u32 pwm_omap_dmtimer_get_clock_cycles(unsigned long clk_rate, int ns)
> {
> return DIV_ROUND_CLOSEST_ULL((u64)clk_rate * ns, NSEC_PER_SEC);
> }
>
> +/**
> + * pwm_omap_dmtimer_start() - Start the pwm omap dm timer in pwm mode
> + * @omap: Pointer to pwm omap dm timer chip
> + */
> static void pwm_omap_dmtimer_start(struct pwm_omap_dmtimer_chip *omap)
> {
> /*
> @@ -67,32 +88,16 @@ static void pwm_omap_dmtimer_start(struct pwm_omap_dmtimer_chip *omap)
> omap->pdata->start(omap->dm_timer);
> }
>
> -static int pwm_omap_dmtimer_enable(struct pwm_chip *chip,
> - struct pwm_device *pwm)
> -{
> - struct pwm_omap_dmtimer_chip *omap = to_pwm_omap_dmtimer_chip(chip);
> -
> - mutex_lock(&omap->mutex);
> - omap->pdata->set_pwm(omap->dm_timer,
> - pwm_get_polarity(pwm) == PWM_POLARITY_INVERSED,
> - true, OMAP_TIMER_TRIGGER_OVERFLOW_AND_COMPARE);
> -
> - pwm_omap_dmtimer_start(omap);
> - mutex_unlock(&omap->mutex);
> -
> - return 0;
> -}
> -
> -static void pwm_omap_dmtimer_disable(struct pwm_chip *chip,
> - struct pwm_device *pwm)
> -{
> - struct pwm_omap_dmtimer_chip *omap = to_pwm_omap_dmtimer_chip(chip);
> -
> - mutex_lock(&omap->mutex);
> - omap->pdata->stop(omap->dm_timer);
> - mutex_unlock(&omap->mutex);
> -}
> -
> +/**
> + * pwm_omap_dmtimer_config() - Update the configuration of pwm omap dm timer
> + * @chip: Pointer to PWM controller
> + * @pwm: Pointer to PWM channel
> + * @duty_ns: New duty cycle in nano seconds
> + * @period_ns: New period in nano seconds
> + *
> + * Return 0 if successfully changed the period/duty_cycle else appropriate
> + * error.
> + */
> static int pwm_omap_dmtimer_config(struct pwm_chip *chip,
> struct pwm_device *pwm,
> int duty_ns, int period_ns)
> @@ -100,30 +105,26 @@ static int pwm_omap_dmtimer_config(struct pwm_chip *chip,
> struct pwm_omap_dmtimer_chip *omap = to_pwm_omap_dmtimer_chip(chip);
> u32 period_cycles, duty_cycles;
> u32 load_value, match_value;
> - struct clk *fclk;
> unsigned long clk_rate;
> + struct clk *fclk;
>
> dev_dbg(chip->dev, "requested duty cycle: %d ns, period: %d ns\n",
> duty_ns, period_ns);
>
> - mutex_lock(&omap->mutex);
> if (duty_ns == pwm_get_duty_cycle(pwm) &&
> - period_ns == pwm_get_period(pwm)) {
> - /* No change - don't cause any transients. */
> - mutex_unlock(&omap->mutex);
> + period_ns == pwm_get_period(pwm))
> return 0;
> - }
>
> fclk = omap->pdata->get_fclk(omap->dm_timer);
> if (!fclk) {
> dev_err(chip->dev, "invalid pmtimer fclk\n");
> - goto err_einval;
> + return -EINVAL;
> }
>
> clk_rate = clk_get_rate(fclk);
> if (!clk_rate) {
> dev_err(chip->dev, "invalid pmtimer fclk rate\n");
> - goto err_einval;
> + return -EINVAL;
> }
>
> dev_dbg(chip->dev, "clk rate: %luHz\n", clk_rate);
> @@ -151,7 +152,7 @@ static int pwm_omap_dmtimer_config(struct pwm_chip *chip,
> dev_info(chip->dev,
> "period %d ns too short for clock rate %lu Hz\n",
> period_ns, clk_rate);
> - goto err_einval;
> + return -EINVAL;
> }
>
> if (duty_cycles < 1) {
> @@ -183,54 +184,72 @@ static int pwm_omap_dmtimer_config(struct pwm_chip *chip,
> dev_dbg(chip->dev, "load value: %#08x (%d), match value: %#08x (%d)\n",
> load_value, load_value, match_value, match_value);
>
> - mutex_unlock(&omap->mutex);
> -
> return 0;
> -
> -err_einval:
> - mutex_unlock(&omap->mutex);
> -
> - return -EINVAL;
> }
>
> -static int pwm_omap_dmtimer_set_polarity(struct pwm_chip *chip,
> - struct pwm_device *pwm,
> - enum pwm_polarity polarity)
> +/**
> + * pwm_omap_dmtimer_apply() - Changes the state of the pwm omap dm timer.
> + * @chip: Pointer to PWM controller
> + * @pwm: Pointer to PWM channel
> + * @state: New sate to apply
> + *
> + * Return 0 if successfully changed the state else appropriate error.
> + */
> +static int pwm_omap_dmtimer_apply(struct pwm_chip *chip,
> + struct pwm_device *pwm,
> + const struct pwm_state *state)
> {
> struct pwm_omap_dmtimer_chip *omap = to_pwm_omap_dmtimer_chip(chip);
> + int ret = 0;
>
> - /*
> - * PWM core will not call set_polarity while PWM is enabled so it's
> - * safe to reconfigure the timer here without stopping it first.
> - */
> mutex_lock(&omap->mutex);
> - omap->pdata->set_pwm(omap->dm_timer,
> - polarity == PWM_POLARITY_INVERSED,
> - true, OMAP_TIMER_TRIGGER_OVERFLOW_AND_COMPARE);
> +
> + if (pwm_is_enabled(pwm) && !state->enabled) {
In my book calling PWM API functions (designed for PWM consumers) is not
so nice. I would prefer you checking the hardware registers or cache the
state locally instead of relying on the core here.
It would be great to have a general description at the top of the driver
(like for example drivers/pwm/pwm-sifive.c) that answers things like:
- Does calling .stop completes the currently running period (it
should)?
- Does changing polarity, duty_cycle and period complete the running
period?
- How does the hardware behave on disable? (i.e. does it output the
state the pin is at in that moment? Does it go High-Z?)
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |
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