[PATCH v5 5/5] clk: clk-mux: implement remuxing on set_rate

James Hogan
2013-06-13T16:06:02Z

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 at lists.infradead.org
---
Changes in v4:

* never pass NULL to determine_rate's best_parent_clk parameter.

Changes in v3:

* rename/invert CLK_SET_RATE_REMUX to CLK_SET_RATE_NO_REPARENT and move
to patch 3.

drivers/clk/clk-mux.c | 1 +
drivers/clk/clk.c | 49 ++++++++++++++++++++++++++++++++++++++++++++
include/linux/clk-provider.h | 3 +++
3 files changed, 53 insertions(+)

diff --git a/drivers/clk/clk-mux.c b/drivers/clk/clk-mux.c
index 25b1734..cecfa01 100644
--- a/drivers/clk/clk-mux.c
+++ b/drivers/clk/clk-mux.c
@@ -100,6 +100,7 @@ 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 52abc3f..30aaaef 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 5500af6..c94385b 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -419,6 +419,9 @@ 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
--
1.8.1.2