Re: [PATCH v5] pwm: atmel: Enable clk when pwm already enabled in bootloader

[Guiting Shen]

On Sat,Jul 15,2023 at 20:12:53PM GMT+8, Uwe Kleine-König wrote:
> On Sat, Jul 15, 2023 at 10:36:53AM +0800, Guiting Shen wrote:
> > The driver would never call clk_enable() if the PWM channel was already
> > enabled in bootloader which lead to dump the warning message "the PWM
> > clock already disabled" when turning off the PWM channel.
> >
> > Add atmel_pwm_enable_clk_if_on() in probe function to enable clock if
> > the PWM channel was already enabled in bootloader.
> >
> > Signed-off-by: Guiting Shen <aarongt.shen@xxxxxxxxx>
> > ---
> >   drivers/pwm/pwm-atmel.c | 50 +++++++++++++++++++++++++++++++++++++++--
> >   1 file changed, 48 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/pwm/pwm-atmel.c b/drivers/pwm/pwm-atmel.c
> > index cdbc23649032..4dd6e1319343 100644
> > --- a/drivers/pwm/pwm-atmel.c
> > +++ b/drivers/pwm/pwm-atmel.c
> > @@ -36,7 +36,7 @@
> >   #define PWM_SR			0x0C
> >   #define PWM_ISR			0x1C
> >   /* Bit field in SR */
> > -#define PWM_SR_ALL_CH_ON	0x0F
> > +#define PWM_SR_ALL_CH_MASK	0x0F
> >   
> >   /* The following register is PWM channel related registers */
> >   #define PWM_CH_REG_OFFSET	0x200
> > @@ -464,6 +464,45 @@ static const struct of_device_id atmel_pwm_dt_ids[] = {
> >   };
> >   MODULE_DEVICE_TABLE(of, atmel_pwm_dt_ids);
> >   
> > +static int atmel_pwm_enable_clk_if_on(struct atmel_pwm_chip *atmel_pwm, bool on)
> > +{
> > +	unsigned int i, cnt = 0;
> > +	int ret = 0;
> > +	u32 sr;
> > +
> > +	sr = atmel_pwm_readl(atmel_pwm, PWM_SR) & PWM_SR_ALL_CH_MASK;
> > +	if (!sr)
> > +		return 0;
> > +
> > +	for (i = 0; i < atmel_pwm->chip.npwm; i++) {
> > +		if (sr & (1 << i))
> > +			cnt++;
> > +	}
>
> If it's just about counting the set bits, there is the function
> bitmap_weight().

Got it, Thank you.


> > +	if (!on)
> > +		goto disable_clk;
> > +
> > +	for (i = 0; i < cnt; i++) {
> > +		ret = clk_enable(atmel_pwm->clk);
> > +		if (ret) {
> > +			dev_err(atmel_pwm->chip.dev,
> > +				"failed to enable clock for pwm #%d: %pe\n",
> > +							i, ERR_PTR(ret));
>
> The output is bogus here. If SR is say 0xc, and the second enable
> fails, it's about pwm #3, but then i is 1.

I would just output the error clock message like this to fix it:
	dev_err(atmel_pwm->chip.dev,
		"failed to enable clock for pwm %pe\n", ERR_PTR(ret));


> > +			cnt = i;
> > +			goto disable_clk;
> > +		}
> > +	}
> > +
> > +	return 0;
> > +
> > +disable_clk:
> > +	while (cnt--)
> > +		clk_disable(atmel_pwm->clk);
> > +
> > +	return ret;
> > +}
> > +
> >   static int atmel_pwm_probe(struct platform_device *pdev)
> >   {
> >   	struct atmel_pwm_chip *atmel_pwm;
>
> Best regards
> Uwe

--
Best regards,
Guiting Shen