Re: [PATCH v3] pwm: atmel: Enable clk when pwm already enabled in bootloader

From: Uwe Kleine-König
Date: Wed Jul 12 2023 - 06:01:22 EST


On Wed, Jul 12, 2023 at 09:45:08AM +0800, Guiting Shen wrote:
> On Wed, Jul 12, 2023 at 04:30:17AM GMT+8, Uwe Kleine-König wrote:
> > Hello,
> >
> > On Wed, Jul 12, 2023 at 04:09:05AM +0800, Guiting Shen wrote:
> >> +static int atmel_pwm_enable_clk_if_on(struct atmel_pwm_chip *atmel_pwm)
> >> +{
> >> + unsigned int i;
> >> + int err;
> >> + u32 sr;
> >> +
> >> + sr = atmel_pwm_readl(atmel_pwm, PWM_SR);
> >> + if (!sr)
> >> + return 0;
> >> +
> >> + for (i = 0; i < atmel_pwm->chip.npwm; i++) {
> >> + if (!(sr & (1 << i)))
> >> + continue;
> >> +
> >> + err = clk_enable(atmel_pwm->clk);
> >> + if (err) {
> >> + dev_err(atmel_pwm->chip.dev,
> >> + "failed to enable clock: %pe\n", ERR_PTR(err));
> >
> > Here you leak possibly a few enables. While it's not likely that the
> > (say) third enable goes wrong, it's also not that hard to handle?!
>
> The driver used the enable_count member of struct clk_core to count the
> PWM channels(4 channels). It will enable hardware clock only when one of
> the PWM channels becomed on from all PWM channels off which maybe return
> error. And in second/third/fourth times to clk_enable(), it just
> increased the enable_count of struct clk_core which would never return
> error.
>
> It maybe confused at first time to view the code.
> Do it need to add something like that: ?
>
> for (i = 0; i < atmel_pwm->chip.npwm; i++) {
> if (!(sr & (1 << i)))
> continue;
>
> err = clk_enable(atmel_pwm->clk);
> if (err) {
> dev_err(atmel_pwm->chip.dev,
> "failed to enable clock: %pe\n", ERR_PTR(err));
>
> for (i = 0; i < cnt; i++)
> clk_disable(atmel_pwm->clk);
> return err;
> }
> cnt++;
> }

Yes, that approx. what I thought of. Maybe also mention i in the error
message? (So something like:

"failed to enable clock for pwm #%d: %pe\n"

Best regards
Uwe

--
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