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drm/radeon: avoid high jitter with small frac divs
Signed-off-by: Christian König <christian.koenig@amd.com>
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parent
695daf1a8e
commit
3b333c5548
1 changed files with 12 additions and 2 deletions
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@ -830,14 +830,14 @@ static void avivo_reduce_ratio(unsigned *nom, unsigned *den,
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/* make sure nominator is large enough */
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if (*nom < nom_min) {
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tmp = (nom_min + *nom - 1) / *nom;
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tmp = DIV_ROUND_UP(nom_min, *nom);
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*nom *= tmp;
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*den *= tmp;
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}
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/* make sure the denominator is large enough */
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if (*den < den_min) {
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tmp = (den_min + *den - 1) / *den;
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tmp = DIV_ROUND_UP(den_min, *den);
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*nom *= tmp;
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*den *= tmp;
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}
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@ -997,6 +997,16 @@ void radeon_compute_pll_avivo(struct radeon_pll *pll,
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/* this also makes sure that the reference divider is large enough */
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avivo_reduce_ratio(&fb_div, &ref_div, fb_div_min, ref_div_min);
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/* avoid high jitter with small fractional dividers */
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if (pll->flags & RADEON_PLL_USE_FRAC_FB_DIV && (fb_div % 10)) {
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fb_div_min = max(fb_div_min, (9 - (fb_div % 10)) * 20 + 60);
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if (fb_div < fb_div_min) {
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unsigned tmp = DIV_ROUND_UP(fb_div_min, fb_div);
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fb_div *= tmp;
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ref_div *= tmp;
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}
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}
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/* and finally save the result */
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if (pll->flags & RADEON_PLL_USE_FRAC_FB_DIV) {
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*fb_div_p = fb_div / 10;
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