Re: [PATCH v3 07/11] pwm: imx: Provide atomic PWM support for i.MX PWMv2

Stefan Agner
2016-11-22T22:08:20Z

On 2016-11-01 00:10, Lukasz Majewski wrote:
> This commit provides apply() callback implementation for i.MX's PWMv2.
>
> Suggested-by: Stefan Agner <stefan@agner.ch>
> Suggested-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> Signed-off-by: Lukasz Majewski <l.majewski@majess.pl>
> Reviewed-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> ---
> Changes for v3:
> - Remove ipg clock enable/disable functions
>
> Changes for v2:
> - None
> ---
> drivers/pwm/pwm-imx.c | 70 +++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 70 insertions(+)
>
> diff --git a/drivers/pwm/pwm-imx.c b/drivers/pwm/pwm-imx.c
> index ebe9b0c..cd53c05 100644
> --- a/drivers/pwm/pwm-imx.c
> +++ b/drivers/pwm/pwm-imx.c
> @@ -159,6 +159,75 @@ static void imx_pwm_wait_fifo_slot(struct pwm_chip *chip,
> }
> }
>
> +static int imx_pwm_apply_v2(struct pwm_chip *chip, struct pwm_device *pwm,
> + struct pwm_state *state)
> +{
> + unsigned long period_cycles, duty_cycles, prescale;
> + struct imx_chip *imx = to_imx_chip(chip);
> + struct pwm_state cstate;
> + unsigned long long c;
> + u32 cr = 0;
> + int ret;
> +
> + pwm_get_state(pwm, &cstate);
> +

Couldn't we do:

if (cstate.enabled) { ...

> + c = clk_get_rate(imx->clk_per);
> + c *= state->period;
> +
> + do_div(c, 1000000000);
> + period_cycles = c;
> +
> + prescale = period_cycles / 0x10000 + 1;
> +
> + period_cycles /= prescale;
> + c = (unsigned long long)period_cycles * state->duty_cycle;
> + do_div(c, state->period);
> + duty_cycles = c;
> +
> + /*
> + * according to imx pwm RM, the real period value should be
> + * PERIOD value in PWMPR plus 2.
> + */
> + if (period_cycles > 2)
> + period_cycles -= 2;
> + else
> + period_cycles = 0;
> +
> + /* Enable the clock if the PWM is being enabled. */
> + if (state->enabled && !cstate.enabled) {
> + ret = clk_prepare_enable(imx->clk_per);
> + if (ret)
> + return ret;
> + }
> +
> + /*
> + * Wait for a free FIFO slot if the PWM is already enabled, and flush
> + * the FIFO if the PWM was disabled and is about to be enabled.
> + */
> + if (cstate.enabled)
> + imx_pwm_wait_fifo_slot(chip, pwm);
> + else if (state->enabled)
> + imx_pwm_sw_reset(chip);
> +
> + writel(duty_cycles, imx->mmio_base + MX3_PWMSAR);
> + writel(period_cycles, imx->mmio_base + MX3_PWMPR);
> +
> + cr |= MX3_PWMCR_PRESCALER(prescale) |
> + MX3_PWMCR_DOZEEN | MX3_PWMCR_WAITEN |
> + MX3_PWMCR_DBGEN | MX3_PWMCR_CLKSRC_IPG_HIGH;
> +
> + if (state->enabled)
> + cr |= MX3_PWMCR_EN;

} else if (state->enabled) {
imx_pwm_sw_reset(chip);
}

and get rid of the if (state->enabled) in between? This would safe us
useless recalculation when disabling the controller...

--
Stefan

> +
> + writel(cr, imx->mmio_base + MX3_PWMCR);
> +
> + /* Disable the clock if the PWM is being disabled. */
> + if (!state->enabled && cstate.enabled)
> + clk_disable_unprepare(imx->clk_per);
> +
> + return 0;
> +}
> +
> static int imx_pwm_config_v2(struct pwm_chip *chip,
> struct pwm_device *pwm, int duty_ns, int period_ns)
> {
> @@ -273,6 +342,7 @@ static struct pwm_ops imx_pwm_ops_v2 = {
> .enable = imx_pwm_enable,
> .disable = imx_pwm_disable,
> .config = imx_pwm_config,
> + .apply = imx_pwm_apply_v2,
> .owner = THIS_MODULE,
> };