[PATCH 2/3] clk: keystone: sci-clk: cache results of last query rate operation

[Tero Kristo]

Cache results of the latest query rate operation. This optimizes the
firmware interface a bit, avoiding unnecessary calls to firmware if we
know the result already; the firmware interface is pretty expensive
to use for query rate functionality.

Signed-off-by: Tero Kristo <t-kristo@xxxxxx>
---
 drivers/clk/keystone/sci-clk.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/clk/keystone/sci-clk.c b/drivers/clk/keystone/sci-clk.c
index f126b6045afa..b6477b08af04 100644
--- a/drivers/clk/keystone/sci-clk.c
+++ b/drivers/clk/keystone/sci-clk.c
@@ -54,6 +54,8 @@ struct sci_clk_provider {
  * @provider:	 Master clock provider
  * @flags:	 Flags for the clock
  * @node:	 Link for handling clocks probed via DT
+ * @cached_req:	 Cached requested freq for determine rate calls
+ * @cached_res:	 Cached result freq for determine rate calls
  */
 struct sci_clk {
 	struct clk_hw hw;
@@ -63,6 +65,8 @@ struct sci_clk {
 	struct sci_clk_provider *provider;
 	u8 flags;
 	struct list_head node;
+	unsigned long cached_req;
+	unsigned long cached_res;
 };
 
 #define to_sci_clk(_hw) container_of(_hw, struct sci_clk, hw)
@@ -175,6 +179,11 @@ static int sci_clk_determine_rate(struct clk_hw *hw,
 	int ret;
 	u64 new_rate;
 
+	if (clk->cached_req && clk->cached_req == req->rate) {
+		req->rate = clk->cached_res;
+		return 0;
+	}
+
 	ret = clk->provider->ops->get_best_match_freq(clk->provider->sci,
 						      clk->dev_id,
 						      clk->clk_id,
@@ -189,6 +198,9 @@ static int sci_clk_determine_rate(struct clk_hw *hw,
 		return ret;
 	}
 
+	clk->cached_req = req->rate;
+	clk->cached_res = new_rate;
+
 	req->rate = new_rate;
 
 	return 0;
@@ -249,6 +261,8 @@ static int sci_clk_set_parent(struct clk_hw *hw, u8 index)
 {
 	struct sci_clk *clk = to_sci_clk(hw);
 
+	clk->cached_req = 0;
+
 	return clk->provider->ops->set_parent(clk->provider->sci, clk->dev_id,
 					      clk->clk_id,
 					      index + 1 + clk->clk_id);
-- 
2.17.1

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