linux-kernel - Re: [PATCH v5 07/11] pwm: imx: Provide atomic PWM support for i.MX PWMv2

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Date:   Mon, 30 Jan 2017 08:54:46 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:     Lukasz Majewski <lukma@...x.de>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Stefan Agner <stefan@...er.ch>, linux-pwm@...r.kernel.org,
        Bhuvanchandra DV <bhuvanchandra.dv@...adex.com>,
        linux-kernel@...r.kernel.org,
        Lothar Wassmann <LW@...o-electronics.de>,
        kernel@...gutronix.de, Fabio Estevam <fabio.estevam@....com>,
        Lukasz Majewski <l.majewski@...ess.pl>
Subject: Re: [PATCH v5 07/11] pwm: imx: Provide atomic PWM support for i.MX
 PWMv2

On Mon, Jan 30, 2017 at 08:49:14AM +0100, Boris Brezillon wrote:
> On Sun, 29 Jan 2017 22:54:11 +0100
> Lukasz Majewski <lukma@...x.de> wrote:
> 
> > This commit provides apply() callback implementation for i.MX's PWMv2.
> > 
> > Suggested-by: Stefan Agner <stefan@...er.ch>
> > Suggested-by: Boris Brezillon <boris.brezillon@...e-electrons.com>
> > Signed-off-by: Lukasz Majewski <l.majewski@...ess.pl>
> > Reviewed-by: Boris Brezillon <boris.brezillon@...e-electrons.com>
> > ---
> > Changes for v5:
> > - Modify ->apply() function to avoid unbalanced clock enabling/disabling
> > - Fix preventing iMX7 from hanging
> > 
> > Changes for v4:
> > - Avoid recalculation of PWM parameters when disabling PWM signal
> > - Unconditionally call clk_prepare_enable(imx->clk_per) and
> >   clk_disable_unprepare(imx->clk_per)
> > 
> > Changes for v3:
> > - Remove ipg clock enable/disable functions
> > 
> > Changes for v2:
> > - None
> > ---
> >  drivers/pwm/pwm-imx.c | 68 +++++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 68 insertions(+)
> > 
> > diff --git a/drivers/pwm/pwm-imx.c b/drivers/pwm/pwm-imx.c
> > index 60cdc5c..fdaa11b 100644
> > --- a/drivers/pwm/pwm-imx.c
> > +++ b/drivers/pwm/pwm-imx.c
> > @@ -249,6 +249,73 @@ static int imx_pwm_config(struct pwm_chip *chip,
> >  	return ret;
> >  }
> >  
> > +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;
> > +	int ret;
> > +
> > +	pwm_get_state(pwm, &cstate);
> > +
> > +	if (state->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;
> > +
> > +		/*
> > +		 * 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) {
> 
> Should just be
> 
> 		} else {
> 
> since we're already in the 'if (state->enabled)' block (see above).
> 
> I see that Thierry already applied the series, so, just for the record,
> with this fixed, the whole series is
> 
> Reviewed-by: Boris Brezillon <boris.brezillon@...e-electrons.com>

I haven't gotten to that patch yet because I need to manually apply a
bunch of these because of the const pwm_ops patch. I'll apply the change
you mentioned and will add your R-b tag.

Thanks,
Thierry

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