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drm/sun4i: dotclock: Round to closest clock rate

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With display pixel clocks we want to have the closest possible clock
rate, to minimize timing and refresh rate skews. Whether the actual
clock rate is higher or lower than the requested rate is less important.

Also check candidates against the requested rate, rather than the
ideal parent rate, the varying dividers also influence the difference
between the requested rate and the rounded rate.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
This commit is contained in:
Chen-Yu Tsai 2016-09-15 23:14:02 +08:00 committed by Maxime Ripard
parent 15ae0ea4bf
commit ac412c3d4f
1 changed files with 2 additions and 1 deletions
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3
drivers/gpu/drm/sun4i/sun4i_dotclock.c
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@ -90,7 +90,8 @@ static long sun4i_dclk_round_rate(struct clk_hw *hw, unsigned long rate,
goto out;
}
if ((rounded < ideal) && (rounded > best_parent)) {
if (abs(rate - rounded / i) <
abs(rate - best_parent / best_div)) {
best_parent = rounded;
best_div = i;
}