diff mbox

[v5,1/7] clk: at91: clk-generated: remove useless divisor loop

Message ID fe26a470c87e39b5e07fbada6ce7020a6b65429b.1502346448.git-series.quentin.schulz@free-electrons.com (mailing list archive)
State New, archived
Headers show

Commit Message

Quentin Schulz Aug. 10, 2017, 6:34 a.m. UTC 
The driver requests the current clk rate of each of its parent clocks to
decide whether a clock rate is suitable or not. It does not request
determine_rate from a parent clock which could request a rate change in
parent clock (i.e. there is no parent rate propagation).

We know the rate we want (passed along req argument of the function) and
the parent clock rate, thus we know the closest rounded divisor, we
don't need to iterate over the available divisors to find the best one
for a given clock.

Signed-off-by: Quentin Schulz <quentin.schulz@free-electrons.com>
Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
---
 drivers/clk/at91/clk-generated.c | 25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)

Comments

Stephen Boyd Sept. 1, 2017, 10:55 p.m. UTC | #1 
On 08/10, Quentin Schulz wrote:
> The driver requests the current clk rate of each of its parent clocks to
> decide whether a clock rate is suitable or not. It does not request
> determine_rate from a parent clock which could request a rate change in
> parent clock (i.e. there is no parent rate propagation).
> 
> We know the rate we want (passed along req argument of the function) and
> the parent clock rate, thus we know the closest rounded divisor, we
> don't need to iterate over the available divisors to find the best one
> for a given clock.
> 
> Signed-off-by: Quentin Schulz <quentin.schulz@free-electrons.com>
> Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
> ---

Applied to clk-next
diff mbox

Patch

diff --git a/drivers/clk/at91/clk-generated.c b/drivers/clk/at91/clk-generated.c
index f0b7ae9..ef4b4e0 100644
--- a/drivers/clk/at91/clk-generated.c
+++ b/drivers/clk/at91/clk-generated.c
@@ -124,19 +124,18 @@  static int clk_generated_determine_rate(struct clk_hw *hw,
 		    (gck->range.max && min_rate > gck->range.max))
 			continue;
 
-		for (div = 1; div < GENERATED_MAX_DIV + 2; div++) {
-			tmp_rate = DIV_ROUND_CLOSEST(parent_rate, div);
-			tmp_diff = abs(req->rate - tmp_rate);
-
-			if (best_diff < 0 || best_diff > tmp_diff) {
-				best_rate = tmp_rate;
-				best_diff = tmp_diff;
-				req->best_parent_rate = parent_rate;
-				req->best_parent_hw = parent;
-			}
-
-			if (!best_diff || tmp_rate < req->rate)
-				break;
+		div = DIV_ROUND_CLOSEST(parent_rate, req->rate);
+		if (!div)
+			tmp_rate = parent_rate;
+		else
+			tmp_rate = parent_rate / div;
+		tmp_diff = abs(req->rate - tmp_rate);
+
+		if (best_diff < 0 || best_diff > tmp_diff) {
+			best_rate = tmp_rate;
+			best_diff = tmp_diff;
+			req->best_parent_rate = parent_rate;
+			req->best_parent_hw = parent;
 		}
 
 		if (!best_diff)