drm/radeon: avoid high jitter with small frac divs (3b333c55) · Commits · e / devices / android_kernel_samsung_universal8890

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;