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clk: k210: Try harder to get the best config

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In some cases, the best config cannot be used because the VCO would be
out-of-spec. In these cases, we may need to try a worse combination of r/od
in order to find the best representable config. This also adds a few test
cases to catch this and other (possible) unlikely errors.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
This commit is contained in:
Sean Anderson 2021-09-11 13:20:03 -04:00 committed by Leo Yu-Chi Liang
parent 6e23c9f0c1
commit 425c08faa8
2 changed files with 28 additions and 0 deletions
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24
drivers/clk/clk_kendryte.c
View file

@ -816,6 +816,30 @@ again:
i--;
}
/*
* Try looking back to see if there is a worse ratio
* that we could try anyway
*/
while (i > 0) {
i--;
new_r = UNPACK_R(factors[i]);
new_od = UNPACK_OD(factors[i]);
/*
* Don't loop over factors for the same product
* to avoid getting stuck because of the above
* clause
*/
if (r * od != new_r * new_od) {
if (new_r * new_od > last_r * last_od) {
r = new_r;
od = new_od;
swapped = false;
goto again;
}
break;
}
}
/* We ran out of things to try */
continue;
}

4
test/dm/k210_pll.c
View file

@ -84,6 +84,10 @@ static int dm_test_k210_pll(struct unit_test_state *uts)
compare(400000000, 26000000);
compare(27000000, 26000000);
compare(26000000, 27000000);
compare(13300000 * 64, 13300000);
compare(21250000, 21250000 * 70);
compare(21250000, 1750000000);
compare(1750000000, 1750000000);
return 0;
}