Re: [PATCH 1/2] pwm: meson: consider 128 a valid pre-divider

[Uwe Kleine-König]

Hello Martin,

On Mon, Apr 01, 2019 at 08:18:16PM +0200, Martin Blumenstingl wrote:
> diff --git a/drivers/pwm/pwm-meson.c b/drivers/pwm/pwm-meson.c
> index f6e738ad7bd9..4b708c1fcb1d 100644
> --- a/drivers/pwm/pwm-meson.c
> +++ b/drivers/pwm/pwm-meson.c
> @@ -188,7 +188,7 @@ static int meson_pwm_calc(struct meson_pwm *meson,
>  	do_div(fin_ps, fin_freq);
>  
>  	/* Calc pre_div with the period */
> -	for (pre_div = 0; pre_div < MISC_CLK_DIV_MASK; pre_div++) {
> +	for (pre_div = 0; pre_div <= MISC_CLK_DIV_MASK; pre_div++) {
>  		cnt = DIV_ROUND_CLOSEST_ULL((u64)period * 1000,
>  					    fin_ps * (pre_div + 1));
>  		dev_dbg(meson->chip.dev, "fin_ps=%llu pre_div=%u cnt=%u\n",

You could even calculate pre_div without the loop.

Something like:

	u64 pre_div = (u64)period * rate;
	do_div_round_up(pre_div, NSEC_PER_SEC * 0xffff);
	pre_div--;

(I didn't check rounding and maybe its off by one and ...) This would
also get rid of the strange 1000 that is currently used in the
calculation without a real benefit (unless I missed something).

Best regards
Uwe

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