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Message-ID: <20201209070516.yw5bpsh474k7mnfx@pengutronix.de>
Date: Wed, 9 Dec 2020 08:05:16 +0100
From: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To: Lino Sanfilippo <LinoSanfilippo@....de>
Cc: thierry.reding@...il.com, lee.jones@...aro.org,
nsaenzjulienne@...e.de, f.fainelli@...il.com, rjui@...adcom.com,
sean@...s.org, sbranden@...adcom.com,
bcm-kernel-feedback-list@...adcom.com, linux-pwm@...r.kernel.org,
linux-rpi-kernel@...ts.infradead.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] pwm: bcm2835: Support apply function for atomic
configuration
Hello Lino,
On Tue, Dec 08, 2020 at 11:01:45PM +0100, Lino Sanfilippo wrote:
> Use the newer .apply function of pwm_ops instead of .config, .enable,
> .disable and .set_polarity. This guarantees atomic changes of the pwm
> controller configuration. It also reduces the size of the driver.
>
> Since now period is a 64 bit value, add an extra check to reject periods
> that exceed the possible max value for the 32 bit register.
>
> This has been tested on a Raspberry PI 4.
This looks right, just two small nitpicks below.
> Signed-off-by: Lino Sanfilippo <LinoSanfilippo@....de>
> ---
>
> v3: Check against period truncation (based on a review by Uwe Kleine-König)
> v2: Fix compiler error for 64 bit builds
>
> drivers/pwm/pwm-bcm2835.c | 72 +++++++++++++++++------------------------------
> 1 file changed, 26 insertions(+), 46 deletions(-)
>
> diff --git a/drivers/pwm/pwm-bcm2835.c b/drivers/pwm/pwm-bcm2835.c
> index 6841dcf..d339898 100644
> --- a/drivers/pwm/pwm-bcm2835.c
> +++ b/drivers/pwm/pwm-bcm2835.c
> @@ -58,13 +58,15 @@ static void bcm2835_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
> writel(value, pc->base + PWM_CONTROL);
> }
>
> -static int bcm2835_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
> - int duty_ns, int period_ns)
> +static int bcm2835_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> + const struct pwm_state *state)
> {
> +
> struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
> unsigned long rate = clk_get_rate(pc->clk);
> + unsigned long long period;
> unsigned long scaler;
> - u32 period;
> + u32 val;
>
> if (!rate) {
> dev_err(pc->dev, "failed to get clock rate\n");
> @@ -72,65 +74,43 @@ static int bcm2835_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
> }
>
> scaler = DIV_ROUND_CLOSEST(NSEC_PER_SEC, rate);
> - period = DIV_ROUND_CLOSEST(period_ns, scaler);
> + /* set period */
> + period = DIV_ROUND_CLOSEST_ULL(state->period, scaler);
>
> - if (period < PERIOD_MIN)
> + /* dont accept a period that is too small or has been truncated */
> + if ((period < PERIOD_MIN) || (period > U32_MAX))
> return -EINVAL;
>
> - writel(DIV_ROUND_CLOSEST(duty_ns, scaler),
> - pc->base + DUTY(pwm->hwpwm));
> - writel(period, pc->base + PERIOD(pwm->hwpwm));
> -
> - return 0;
> -}
> -
> -static int bcm2835_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
> -{
> - struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
> - u32 value;
> -
> - value = readl(pc->base + PWM_CONTROL);
> - value |= PWM_ENABLE << PWM_CONTROL_SHIFT(pwm->hwpwm);
> - writel(value, pc->base + PWM_CONTROL);
> -
> - return 0;
> -}
> -
> -static void bcm2835_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
> -{
> - struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
> - u32 value;
> + writel((u32) period, pc->base + PERIOD(pwm->hwpwm));
This cast isn't necessary. (And if it was, I *think* the space between
"(u32)" and "period" is wrong. But my expectation that checkpatch warns
about this is wrong, so take this with a grain of salt.)
> - value = readl(pc->base + PWM_CONTROL);
> - value &= ~(PWM_ENABLE << PWM_CONTROL_SHIFT(pwm->hwpwm));
> - writel(value, pc->base + PWM_CONTROL);
> -}
> + /* set duty cycle */
> + val = DIV_ROUND_CLOSEST_ULL(state->duty_cycle, scaler);
> + writel(val, pc->base + DUTY(pwm->hwpwm));
>
> -static int bcm2835_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
> - enum pwm_polarity polarity)
> -{
> - struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
> - u32 value;
> + /* set polarity */
> + val = readl(pc->base + PWM_CONTROL);
>
> - value = readl(pc->base + PWM_CONTROL);
> + if (state->polarity == PWM_POLARITY_NORMAL)
> + val &= ~(PWM_POLARITY << PWM_CONTROL_SHIFT(pwm->hwpwm));
> + else
> + val |= PWM_POLARITY << PWM_CONTROL_SHIFT(pwm->hwpwm);
>
> - if (polarity == PWM_POLARITY_NORMAL)
> - value &= ~(PWM_POLARITY << PWM_CONTROL_SHIFT(pwm->hwpwm));
> + /* enable/disable */
> + if (state->enabled)
> + val |= PWM_ENABLE << PWM_CONTROL_SHIFT(pwm->hwpwm);
> else
> - value |= PWM_POLARITY << PWM_CONTROL_SHIFT(pwm->hwpwm);
> + val &= ~(PWM_ENABLE << PWM_CONTROL_SHIFT(pwm->hwpwm));
>
> - writel(value, pc->base + PWM_CONTROL);
> + writel(val, pc->base + PWM_CONTROL);
>
> return 0;
> }
>
> +
I wouldn't have added this empty line. But I guess that's subjective. Or
did you add this by mistake?
> static const struct pwm_ops bcm2835_pwm_ops = {
> .request = bcm2835_pwm_request,
> .free = bcm2835_pwm_free,
> - .config = bcm2835_pwm_config,
> - .enable = bcm2835_pwm_enable,
> - .disable = bcm2835_pwm_disable,
> - .set_polarity = bcm2835_set_polarity,
> + .apply = bcm2835_pwm_apply,
> .owner = THIS_MODULE,
> };
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |
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