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clk: rockchip: half-divider: Use maximal and best divider

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The bigger the divider, the better the clock jitter.

Change-Id: I4b4e06c71c2f0bdb0e32422fb42c8d490c3ec4bd
Signed-off-by: Finley Xiao <finley.xiao@rock-chips.com>
Signed-off-by: Elaine Zhang <zhangqing@rock-chips.com>
This commit is contained in:
Finley Xiao
2018-06-25 18:06:41 +08:00
committed by Tao Huang
parent 75ec41628c
commit 58b846439b
1 changed files with 7 additions and 15 deletions
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22
drivers/clk/rockchip/clk-half-divider.c
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@@ -14,9 +14,9 @@ static bool _is_best_half_div(unsigned long rate, unsigned long now,
unsigned long best, unsigned long flags)
{
if (flags & CLK_DIVIDER_ROUND_CLOSEST)
return abs(rate - now) < abs(rate - best);
return abs(rate - now) <= abs(rate - best);
return now <= rate && now > best;
return now <= rate && now >= best;
}
static unsigned long clk_half_divider_recalc_rate(struct clk_hw *hw,
@@ -38,7 +38,7 @@ static int clk_half_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
{
unsigned int i, bestdiv = 0;
unsigned long parent_rate, best = 0, now, maxdiv;
unsigned long parent_rate_saved = *best_parent_rate;
bool is_bestdiv = false;
if (!rate)
rate = 1;
@@ -51,7 +51,7 @@ static int clk_half_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
if (bestdiv < 3)
bestdiv = 0;
else
bestdiv = (bestdiv - 3) / 2;
bestdiv = DIV_ROUND_UP(bestdiv - 3, 2);
bestdiv = bestdiv > maxdiv ? maxdiv : bestdiv;
return bestdiv;
}
@@ -63,28 +63,20 @@ static int clk_half_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
maxdiv = min(ULONG_MAX / rate, maxdiv);
for (i = 0; i <= maxdiv; i++) {
if (((u64)rate * (i * 2 + 3)) == ((u64)parent_rate_saved * 2)) {
/*
* It's the most ideal case if the requested rate can be
* divided from parent clock without needing to change
* parent rate, so return the divider immediately.
*/
*best_parent_rate = parent_rate_saved;
return i;
}
parent_rate = clk_hw_round_rate(clk_hw_get_parent(hw),
((u64)rate * (i * 2 + 3)) / 2);
now = DIV_ROUND_UP_ULL(((u64)parent_rate * 2),
(i * 2 + 3));
if (_is_best_half_div(rate, now, best, flags)) {
is_bestdiv = true;
bestdiv = i;
best = now;
*best_parent_rate = parent_rate;
}
}
if (!bestdiv) {
if (!is_bestdiv) {
bestdiv = div_mask(width);
*best_parent_rate = clk_hw_round_rate(clk_hw_get_parent(hw), 1);
}
@@ -114,7 +106,7 @@ static int clk_half_divider_set_rate(struct clk_hw *hw, unsigned long rate,
u32 val;
value = DIV_ROUND_UP_ULL(((u64)parent_rate * 2), rate);
value = (value - 3) / 2;
value = DIV_ROUND_UP(value - 3, 2);
value = min_t(unsigned int, value, div_mask(divider->width));
if (divider->lock)