clk: clk-mux: implement remuxing on set_rate

Implement clk-mux remuxing if the CLK_SET_RATE_NO_REPARENT flag isn't
set. This implements determine_rate for clk-mux to propagate to each
parent and to choose the best one (like clk-divider this chooses the
parent which provides the fastest rate <= the requested rate).

The determine_rate op is implemented as a core helper function so that
it can be easily used by more complex clocks which incorporate muxes.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Cc: Mike Turquette <mturquette@linaro.org>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Mike Turquette <mturquette@linaro.org>

3 files changed, 53 insertions, 0 deletions

diff --git a/drivers/clk/clk-mux.c b/drivers/clk/clk-mux.c
index b918dc370bd0..0811633fcc4d 100644
--- a/drivers/clk/clk-mux.c
+++ b/drivers/clk/clk-mux.c
@@ -104,6 +104,7 @@ static int clk_mux_set_parent(struct clk_hw *hw, u8 index)
 const struct clk_ops clk_mux_ops = {
         .get_parent = clk_mux_get_parent,
         .set_parent = clk_mux_set_parent,
+        .determine_rate = __clk_mux_determine_rate,
 };
 EXPORT_SYMBOL_GPL(clk_mux_ops);
 
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index f33f1ccf1b2f..bc020372106b 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -692,6 +692,55 @@ struct clk *__clk_lookup(const char *name)
         return NULL;
 }
 
+/*
+ * Helper for finding best parent to provide a given frequency. This can be used
+ * directly as a determine_rate callback (e.g. for a mux), or from a more
+ * complex clock that may combine a mux with other operations.
+ */
+long __clk_mux_determine_rate(struct clk_hw *hw, unsigned long rate,
+                              unsigned long *best_parent_rate,
+                              struct clk **best_parent_p)
+{
+        struct clk *clk = hw->clk, *parent, *best_parent = NULL;
+        int i, num_parents;
+        unsigned long parent_rate, best = 0;
+
+        /* if NO_REPARENT flag set, pass through to current parent */
+        if (clk->flags & CLK_SET_RATE_NO_REPARENT) {
+                parent = clk->parent;
+                if (clk->flags & CLK_SET_RATE_PARENT)
+                        best = __clk_round_rate(parent, rate);
+                else if (parent)
+                        best = __clk_get_rate(parent);
+                else
+                        best = __clk_get_rate(clk);
+                goto out;
+        }
+
+        /* find the parent that can provide the fastest rate <= rate */
+        num_parents = clk->num_parents;
+        for (i = 0; i < num_parents; i++) {
+                parent = clk_get_parent_by_index(clk, i);
+                if (!parent)
+                        continue;
+                if (clk->flags & CLK_SET_RATE_PARENT)
+                        parent_rate = __clk_round_rate(parent, rate);
+                else
+                        parent_rate = __clk_get_rate(parent);
+                if (parent_rate <= rate && parent_rate > best) {
+                        best_parent = parent;
+                        best = parent_rate;
+                }
+        }
+
+out:
+        if (best_parent)
+                *best_parent_p = best_parent;
+        *best_parent_rate = best;
+
+        return best;
+}
+
 /***        clk api        ***/
 
 void __clk_unprepare(struct clk *clk)
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 5c0bc3904c9b..1f0285b2f422 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -436,6 +436,9 @@ unsigned long __clk_get_flags(struct clk *clk);
 bool __clk_is_prepared(struct clk *clk);
 bool __clk_is_enabled(struct clk *clk);
 struct clk *__clk_lookup(const char *name);
+long __clk_mux_determine_rate(struct clk_hw *hw, unsigned long rate,
+                              unsigned long *best_parent_rate,
+                              struct clk **best_parent_p);
 
 /*
  * FIXME clock api without lock protection