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Groups > linux.kernel > #1680898

[PATCH v2 1/9] clk: at91: clk-generated: remove useless divisor loop

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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>
---
 drivers/clk/at91/clk-generated.c | 25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/drivers/clk/at91/clk-generated.c b/drivers/clk/at91/clk-generated.c
index 07c8f701e51c..dab7002937e6 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)
-- 
2.11.0

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[PATCH v2 0/9] add support for Sama5d2 audio PLLs and enable ClassD Quentin Schulz <quentin.schulz@free-electrons.com> - 2017-07-04 14:10 +0200
  [PATCH v2 1/9] clk: at91: clk-generated: remove useless divisor loop Quentin Schulz <quentin.schulz@free-electrons.com> - 2017-07-04 14:10 +0200
  [PATCH v2 4/9] ARM: dts: at91: sama5d2: add classd nodes Quentin Schulz <quentin.schulz@free-electrons.com> - 2017-07-04 14:10 +0200
  [PATCH v2 8/9] ASoC: atmel-classd: remove aclk clock Quentin Schulz <quentin.schulz@free-electrons.com> - 2017-07-04 14:10 +0200
    Re: [PATCH v2 8/9] ASoC: atmel-classd: remove aclk clock Mark Brown <broonie@kernel.org> - 2017-07-07 14:50 +0200
  [PATCH v2 7/9] ASoC: atmel-classd: remove aclk clock from DT binding Quentin Schulz <quentin.schulz@free-electrons.com> - 2017-07-04 14:10 +0200
    Re: [PATCH v2 7/9] ASoC: atmel-classd: remove aclk clock from DT  binding Mark Brown <broonie@kernel.org> - 2017-07-07 14:50 +0200
    Re: [PATCH v2 7/9] ASoC: atmel-classd: remove aclk clock from DT  binding Rob Herring <robh@kernel.org> - 2017-07-10 03:10 +0200
  [PATCH v2 3/9] clk: at91: add audio pll clock drivers Quentin Schulz <quentin.schulz@free-electrons.com> - 2017-07-04 14:10 +0200
  [PATCH v2 2/9] clk: at91: add audio plls to the compatible list in DT binding Quentin Schulz <quentin.schulz@free-electrons.com> - 2017-07-04 14:10 +0200

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