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clk: bcm/kona: implement determine_rate()

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Implement the clk->determine_rate method for Broadcom Kona peripheral
clocks.  This allows a peripheral clock to be re-parented in order to
satisfy a rate change request.  This takes the place of the previous
kona_peri_clk_round_rate() functionality, though that function remains
because it is used by the new one.

The parent clock that allows the peripheral clock to produce a rate
closest to the one requested is the one selected, though the current
parent is used by default.

Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Mike Turquette <mturquette@linaro.org>
This commit is contained in:
Alex Elder 2014-05-27 11:56:56 -05:00 committed by Mike Turquette
parent 63a00269cb
commit c2152d0e4d
1 changed files with 53 additions and 1 deletions
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54
drivers/clk/bcm/clk-kona.c
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@ -1031,6 +1031,58 @@ static long kona_peri_clk_round_rate(struct clk_hw *hw, unsigned long rate,
rate ? rate : 1, *parent_rate, NULL);
}
static long kona_peri_clk_determine_rate(struct clk_hw *hw, unsigned long rate,
unsigned long *best_parent_rate, struct clk **best_parent)
{
struct kona_clk *bcm_clk = to_kona_clk(hw);
struct clk *clk = hw->clk;
struct clk *current_parent;
unsigned long parent_rate;
unsigned long best_delta;
unsigned long best_rate;
u32 parent_count;
u32 which;
/*
* If there is no other parent to choose, use the current one.
* Note: We don't honor (or use) CLK_SET_RATE_NO_REPARENT.
*/
WARN_ON_ONCE(bcm_clk->init_data.flags & CLK_SET_RATE_NO_REPARENT);
parent_count = (u32)bcm_clk->init_data.num_parents;
if (parent_count < 2)
return kona_peri_clk_round_rate(hw, rate, best_parent_rate);
/* Unless we can do better, stick with current parent */
current_parent = clk_get_parent(clk);
parent_rate = __clk_get_rate(current_parent);
best_rate = kona_peri_clk_round_rate(hw, rate, &parent_rate);
best_delta = abs(best_rate - rate);
/* Check whether any other parent clock can produce a better result */
for (which = 0; which < parent_count; which++) {
struct clk *parent = clk_get_parent_by_index(clk, which);
unsigned long delta;
unsigned long other_rate;
BUG_ON(!parent);
if (parent == current_parent)
continue;
/* We don't support CLK_SET_RATE_PARENT */
parent_rate = __clk_get_rate(parent);
other_rate = kona_peri_clk_round_rate(hw, rate, &parent_rate);
delta = abs(other_rate - rate);
if (delta < best_delta) {
best_delta = delta;
best_rate = other_rate;
*best_parent = parent;
*best_parent_rate = parent_rate;
}
}
return best_rate;
}
static int kona_peri_clk_set_parent(struct clk_hw *hw, u8 index)
{
struct kona_clk *bcm_clk = to_kona_clk(hw);
@ -1135,7 +1187,7 @@ struct clk_ops kona_peri_clk_ops = {
.disable = kona_peri_clk_disable,
.is_enabled = kona_peri_clk_is_enabled,
.recalc_rate = kona_peri_clk_recalc_rate,
.round_rate = kona_peri_clk_round_rate,
.determine_rate = kona_peri_clk_determine_rate,
.set_parent = kona_peri_clk_set_parent,
.get_parent = kona_peri_clk_get_parent,
.set_rate = kona_peri_clk_set_rate,