Commit 3b333c55 authored by Christian König's avatar Christian König
Browse files

drm/radeon: avoid high jitter with small frac divs 



Signed-off-by: default avatarChristian König <christian.koenig@amd.com>
parent 695daf1a

drivers/gpu/drm/radeon/radeon_display.c

+12 −2
Original line number Diff line number Diff line
@@ -830,14 +830,14 @@ static void avivo_reduce_ratio(unsigned *nom, unsigned *den, 


	/* make sure nominator is large enough */

        if (*nom < nom_min) {

		tmp = (nom_min + *nom - 1) / *nom;

		tmp = DIV_ROUND_UP(nom_min, *nom);

		*nom *= tmp;

		*den *= tmp;

	}



	/* make sure the denominator is large enough */

	if (*den < den_min) {

		tmp = (den_min + *den - 1) / *den;

		tmp = DIV_ROUND_UP(den_min, *den);

		*nom *= tmp;

		*den *= tmp;

	}
@@ -997,6 +997,16 @@ void radeon_compute_pll_avivo(struct radeon_pll *pll, 
	/* this also makes sure that the reference divider is large enough */

	avivo_reduce_ratio(&fb_div, &ref_div, fb_div_min, ref_div_min);



	/* avoid high jitter with small fractional dividers */

	if (pll->flags & RADEON_PLL_USE_FRAC_FB_DIV && (fb_div % 10)) {

		fb_div_min = max(fb_div_min, (9 - (fb_div % 10)) * 20 + 60);

		if (fb_div < fb_div_min) {

			unsigned tmp = DIV_ROUND_UP(fb_div_min, fb_div);

			fb_div *= tmp;

			ref_div *= tmp;

		}

	}



	/* and finally save the result */

	if (pll->flags & RADEON_PLL_USE_FRAC_FB_DIV) {

		*fb_div_p = fb_div / 10;