clk: k210: Try harder to get the best config

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>

diff --git a/drivers/clk/clk_kendryte.c b/drivers/clk/clk_kendryte.c
index 69691c4..97efda5 100644 (file)
--- a/drivers/clk/clk_kendryte.c
+++ b/drivers/clk/clk_kendryte.c
@@ -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;
                }

diff --git a/test/dm/k210_pll.c b/test/dm/k210_pll.c
index 5574ac9..f55379f 100644 (file)
--- a/test/dm/k210_pll.c
+++ b/test/dm/k210_pll.c
@@ -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;
 }