drm/radeon: avoid high jitter with small frac divs
Signed-off-by: Christian König <christian.koenig@amd.com>
diff --git a/drivers/gpu/drm/radeon/radeon_display.c b/drivers/gpu/drm/radeon/radeon_display.c
index 14bd701..9ff0e2f 100644
--- a/drivers/gpu/drm/radeon/radeon_display.c
+++ b/drivers/gpu/drm/radeon/radeon_display.c
@@ -830,14 +830,14 @@
/* 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 @@
/* 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;
