+ /* No best (r,n,p) yet */
+ if (best->p == 0) {
+ best->p = p;
+ best->n2 = n2;
+ best->r2 = r2;
+ return;
+ }
+
+ /*
+ * Output clock is (LC_FREQ_2K / 2000) * N / (P * R), which compares to
+ * freq2k.
+ *
+ * delta = 1e6 *
+ * abs(freq2k - (LC_FREQ_2K * n2/(p * r2))) /
+ * freq2k;
+ *
+ * and we would like delta <= budget.
+ *
+ * If the discrepancy is above the PPM-based budget, always prefer to
+ * improve upon the previous solution. However, if you're within the
+ * budget, try to maximize Ref * VCO, that is N / (P * R^2).
+ */
+ a = freq2k * budget * p * r2;
+ b = freq2k * budget * best->p * best->r2;
+ diff = ABS_DIFF((freq2k * p * r2), (LC_FREQ_2K * n2));
+ diff_best = ABS_DIFF((freq2k * best->p * best->r2),
+ (LC_FREQ_2K * best->n2));
+ c = 1000000 * diff;
+ d = 1000000 * diff_best;
+
+ if (a < c && b < d) {
+ /* If both are above the budget, pick the closer */
+ if (best->p * best->r2 * diff < p * r2 * diff_best) {
+ best->p = p;
+ best->n2 = n2;
+ best->r2 = r2;
+ }
+ } else if (a >= c && b < d) {
+ /* If A is below the threshold but B is above it? Update. */
+ best->p = p;
+ best->n2 = n2;
+ best->r2 = r2;
+ } else if (a >= c && b >= d) {
+ /* Both are below the limit, so pick the higher n2/(r2*r2) */
+ if (n2 * best->r2 * best->r2 > best->n2 * r2 * r2) {
+ best->p = p;
+ best->n2 = n2;
+ best->r2 = r2;
+ }
+ }
+ /* Otherwise a < c && b >= d, do nothing */
+}
+
+static void
+intel_ddi_calculate_wrpll(int clock /* in Hz */,
+ unsigned *r2_out, unsigned *n2_out, unsigned *p_out)
+{
+ uint64_t freq2k;
+ unsigned p, n2, r2;
+ struct wrpll_rnp best = { 0, 0, 0 };
+ unsigned budget;
+
+ freq2k = clock / 100;
+
+ budget = wrpll_get_budget_for_freq(clock);
+
+ /* Special case handling for 540 pixel clock: bypass WR PLL entirely
+ * and directly pass the LC PLL to it. */
+ if (freq2k == 5400000) {
+ *n2_out = 2;
+ *p_out = 1;
+ *r2_out = 2;
+ return;
+ }