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clk: sunxi-ng: nkm: consider alternative parent rates when determining rate

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In case the CLK_SET_RATE_PARENT flag is set, consider using a different
parent rate when determining a new rate.

To find the best match for the requested rate, perform the following
steps for each NKM combination:
 - calculate the optimal parent rate,
 - find the best parent rate that the parent clock actually supports
 - use that parent rate to calculate the effective rate.

In case the clk does not support setting the parent rate, use the same
algorithm as before.

Acked-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Frank Oltmanns <frank@oltmanns.dev>
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Link: https://lore.kernel.org/r/20230807-pll-mipi_set_rate_parent-v6-2-f173239a4b59@oltmanns.dev
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
This commit is contained in:
Frank Oltmanns 2023-08-07 14:43:35 +02:00 committed by Chen-Yu Tsai
parent 80c439cd1f
commit 3492e4f6db
1 changed files with 43 additions and 1 deletions
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44
drivers/clk/sunxi-ng/ccu_nkm.c
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@ -16,6 +16,45 @@ struct _ccu_nkm {
unsigned long m, min_m, max_m;
};
static unsigned long ccu_nkm_find_best_with_parent_adj(struct clk_hw *parent_hw,
unsigned long *parent, unsigned long rate,
struct _ccu_nkm *nkm)
{
unsigned long best_rate = 0, best_parent_rate = *parent, tmp_parent = *parent;
unsigned long best_n = 0, best_k = 0, best_m = 0;
unsigned long _n, _k, _m;
for (_k = nkm->min_k; _k <= nkm->max_k; _k++) {
for (_n = nkm->min_n; _n <= nkm->max_n; _n++) {
for (_m = nkm->min_m; _m <= nkm->max_m; _m++) {
unsigned long tmp_rate;
tmp_parent = clk_hw_round_rate(parent_hw, rate * _m / (_n * _k));
tmp_rate = tmp_parent * _n * _k / _m;
if (tmp_rate > rate)
continue;
if ((rate - tmp_rate) < (rate - best_rate)) {
best_rate = tmp_rate;
best_parent_rate = tmp_parent;
best_n = _n;
best_k = _k;
best_m = _m;
}
}
}
}
nkm->n = best_n;
nkm->k = best_k;
nkm->m = best_m;
*parent = best_parent_rate;
return best_rate;
}
static unsigned long ccu_nkm_find_best(unsigned long parent, unsigned long rate,
struct _ccu_nkm *nkm)
{
@ -124,7 +163,10 @@ static unsigned long ccu_nkm_round_rate(struct ccu_mux_internal *mux,
if (nkm->common.features & CCU_FEATURE_FIXED_POSTDIV)
rate *= nkm->fixed_post_div;
rate = ccu_nkm_find_best(*parent_rate, rate, &_nkm);
if (!clk_hw_can_set_rate_parent(&nkm->common.hw))
rate = ccu_nkm_find_best(*parent_rate, rate, &_nkm);
else
rate = ccu_nkm_find_best_with_parent_adj(parent_hw, parent_rate, rate, &_nkm);
if (nkm->common.features & CCU_FEATURE_FIXED_POSTDIV)
rate /= nkm->fixed_post_div;