clk: renesas: div6: Consider all parents for requested rate

Currently the .determine_rate() callback considers only the current
parent clock, limiting the range of achievable clock rates on DIV6
clocks with multiple parents, as found on SH/R-Mobile SoCs.

Extend the callback to consider all available parent clocks.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/60e639692b462f99e0b6ab868c3675b3d97dbdb0.1617281699.git.geert+renesas@glider.be

diff --git a/drivers/clk/renesas/clk-div6.c b/drivers/clk/renesas/clk-div6.c
index 3af65ef..a9ac2a8 100644 (file)
--- a/drivers/clk/renesas/clk-div6.c
+++ b/drivers/clk/renesas/clk-div6.c
@@ -103,10 +103,39 @@ static unsigned int cpg_div6_clock_calc_div(unsigned long rate,
 static int cpg_div6_clock_determine_rate(struct clk_hw *hw,
                                         struct clk_rate_request *req)
 {
-       unsigned int div = cpg_div6_clock_calc_div(req->rate,
-                                                  req->best_parent_rate);
+       unsigned long prate, calc_rate, diff, best_rate, best_prate;
+       unsigned int num_parents = clk_hw_get_num_parents(hw);
+       struct clk_hw *parent, *best_parent = NULL;
+       unsigned long min_diff = ULONG_MAX;
+       unsigned int i, div;
+
+       for (i = 0; i < num_parents; i++) {
+               parent = clk_hw_get_parent_by_index(hw, i);
+               if (!parent)
+                       continue;
+
+               prate = clk_hw_get_rate(parent);
+               if (!prate)
+                       continue;
+
+               div = cpg_div6_clock_calc_div(req->rate, prate);
+               calc_rate = prate / div;
+               diff = calc_rate > req->rate ? calc_rate - req->rate
+                                            : req->rate - calc_rate;
+               if (diff < min_diff) {
+                       best_rate = calc_rate;
+                       best_parent = parent;
+                       best_prate = prate;
+                       min_diff = diff;
+               }
+       }
+
+       if (!best_parent)
+               return -EINVAL;
 
-       req->rate = req->best_parent_rate / div;
+       req->best_parent_rate = best_prate;
+       req->best_parent_hw = best_parent;
+       req->rate = best_rate;
        return 0;
 }